How we survived the Harbor Freight assembly manual, and modified our greenhouse to withstand New Mexico winds (so far)...

Sunday, August 19, 2007

Part Seven: Greenhouse Enhancements

This part will be a rambling list of things we've added to the greenhouse. It will probably never end. :-)

Benches and Shelves
I wanted a long bench on each side of the greenhouse, and several additional peninsula-style benches attached to the south bench. I was thinking of simple pine 2x4 frames with a hardware cloth top, but my husband’s design was much more graceful.

They should provide lots of space for pots on top, and lots of free space underneath. They aren't movable, however, so I spent lots of time scribbling on graph paper before we started, and it took a little math!

We started the greenhouse benches before the greenhouse panels were up (much cooler for us to dig the concrete footings.) Each long side bench is supported by two pressure-treated 4x4s, buried 24" deep and set in concrete.

The next day, two horizontal Douglas Fir 4x4's were clamped to either side of the two pressure treated posts. We checked for level, and then temporaried with long screws.

The horizontal 4x4’s were attached by using a 12" long 3/8" drill bit to drill a hole through all three 4x4's. A length of 3/8" all-threads rod was inserted in the hole, and capped on each end with a washer and nut.

The completed bench support for the north wall. It’s a bit over 10’ long. When the redwood slats are added to the top of the horizontal 4x4's, the benches will be 30” tall.

Bench supports after staining. The posts are pressure-treated pine, the horizontal beams are fir, and the top horizontal slats will be redwood. I used a redwood-colored stain to blend the different woods together. I doubt the color will hold up to our sun, but it’ll look nice for a while.

The floor is also in place in this photo. The 12" x 12" concrete pavers weren't very expensive, and should be easy to walk on. We chose gravel in a color complementary to the pavers, and in a size large enough to not get constantly stuck in our shoe treads.

Eventually, we'll do some kind of outdoor threshold to eliminate stepping over the greenhouse frame base. I trip over that daily.

The slats for the bench tops were ripped from 2” by 6” by 12’ redwood. Each resulting slat is 1 ¾” by 1 ½”. We knocked the sharp edges down with a rasp, and sanded them. We used a template to mark the location of the screws, and drilled pilot holes with a drill press.

They were sealed with two coats of stain before attaching, and one more coat on the top surfaces after installation. I used a penetrating oil waterproofing sealant, Olympus Maximum Redwood Naturaltone. Here’s a pile of redwood slats waiting to be installed.

Slats are laid out and temporarily propped up before we build more legs. We decided to cut a few more slats to reduce the spacing between the slats to roughly 3/4" seemed less tippy for small pots.

Completed bench on the south side, with 16” rubber-coated closet shelf from Lowes in place.I bought the “close mesh” which has ½” spacing between the wires. The standard mesh has 7/8” spacing between the wires, and I thought that would be too tippy for 4” pots.

We were concerned the ClosetMaid shelves and braces would not support large numbers of heavy clay pots (especially on a 16” deep shelf.)

So, we used a combination of ClosetMaid braces (the thin white diagonal braces barely visible in the photo above) and wooden support posts.

First, we positioned the shelf so it sat directly on top of the horizontal wall braces (Part 30) and secured it to the top of the hollow brace with screws.

We added a 1”x2” piece of wood behind the front shelf edge to strengthen the outer edge, and to give the posts something to support.

The vertical 2x2" posts were notched at the top so the shelf weight sits directly on the post. Screws go through the post front, through the shelf front, and into the 1x2 wood, tying all three parts together.

The bottom of each vertical post is also screwed to the top of our wooden benches.

There were a few spots requiring the use of bolt cutters to notch out some of the wires, to avoid diagonal wall braces.

In one corner we were able to also support the side of the shelf by resting it on the horizontal braces of the back wall, but we also added a wooden post as well.

This is how it looked after I moved the plants onto the south benches and south shelf.

Installing shelves on the north wall was much more difficult because of the ¾” polyisocyanurate insulation I’ve installed on that entire wall (more about that soon.)

We had to locate the wall studs behind the foam insulation, and cut small holes through the insulation to insert T-bolts into the studs. We found we had to use bolts that varied from 2 ½” to 3”, depending on where they were in the wall.

Once the bolts were in place and firmly secured, we could attach 1x6 boards to the bolts, which gave us a broader surface area to mount shelves. More washers and nuts to secure the boards...

The back of the 16” ClosetMaid shelf rests on the top edge of the 1x6”, and is attached with screws into the top edge of the wooden board.

Then we attached a wooden1x2 to the front of the shelf, just as we did on the south side shelving.

Finally, we added three notched wooden 2x2" posts to support the shelf weight, and screwed them to the wooden benches below.

This is how the north side looked after moving the plants in.

We also planned a potting area with sink on the north wall.

I decided to try my hand at a mosaic countertop. I had a lot of floor tile pieces left over from our house, and other odd tile scraps.

I had fun doing it (and I learned a lot about what a challenge it can be to keep the tiles of varying thicknesses even and smooth on a countertop!) Here is the countertop in progress in my work room.

The finished countertop and sink installed.

The sink drain isn’t connected to our house plumbing. It drains into a gravel pit we dug in the floor, and the soil beneath the gravel is the coarse sand of our yard. Another option for the future would be to route the drain water through the wall of the greenhouse and outdoors, to water a planting bed.

In addition to the sink, I also have a faucet under the bench where I can attach a hose.

I can brush potting soil into the hole in the center, where it falls into a plastic bin below. I keep the hole covered by a removable grill. It's actually a cheap metal trivet I bought at Hobby Lobby, painted it with acrylic paints to blend in a bit with the tile color.

That's the benches/shelves/sink to date...I have a feeling I'll eventually add another tier of low shelves under the benches for shade-loving plants.

There's never enough room for plants.


Insulating the North Wall

The north wall of my greenhouse allows very little light because it faces our house. I decided to install insulation on that wall to reduce the square footage of walls that would easily lose heat in the winter. Many folks install opaque insulation on the north wall, the lower half of the north roof, and partial sections of the other walls, but for this year I'm starting with the north wall only.

Let's pause here for an Embarrassing Newbie Admission. I'm having a bit of a hard time with the looks of all the best insulating and heat-reflecting materials. Sometimes I worry my greenhouse will look more like a NASA laboratory than a pretty gardening space. (No offense, NASA.) I figure one winter of high heating bills will cure that; come Spring, I'll be slapping reflective foil insulation and bubble wrap everywhere. OK, back to more serious details.

Tip: Before installing the insulation, now would be a good time to do any last-minute checking for loose bolts, or gaps that need caulking. Our first rain did reveal some gaps in the frame (especially at the top of all four corner posts, and at the seam in the center of one gutter, which allowed some water to run a central wall stud.) I'm using a gray silicone caulk made for caulking aluminum.

We used polyisocyanurate foil-faced foam sheeting. I couldn’t find 1” thick, so we used ¾” thick, which has an R-value of 5. I purchased three 4’x8’ sheets at Lowe’s for about $12 each. Mine had foil on one side, facing the interior. My plan was to install three pieces vertically, but I found they couldn’t be maneuvered into place because of our EMT braces overhead, and our bench supports below. (These insulation panels don't flex, and they're brittle.) Instead of unbolting the bench supports, I cut the pieces differently.

This stuff cuts easily with a box knife. I put the pieces in place for a dry fit, and found they would sit nicely on the ledge of our pressure treated wood base (dumb luck, not good planning.)

I used an X-acto knife to notch around a few of the EMT braces at the top of the wall.

After I had the panels cut to fit, I removed them and covered all the raw edges with aluminum tape. (I read this helps for insulation purposes, but don’t look to me for a scientific explanation.)

The inside surface is foil, but the outer side is a plastic/paper sheet with big blue lettering that looked awful on the outside of the greenhouse. So, I rolled a coat of white paint on the outside of the panels to cover the lettering.

When the panels were back in place, I covered the seams with aluminum tape. I hoped the fit would be so perfect the panels would just wedge into place, but no luck. I found I needed to add a few screws with washers to keep the wall of insulation snugged up to the frame. We aimed for the hollow horizontal braces, pre-drilled a hole through the foam and the brace, and inserted a screw and washers in a few spots.

North wall taped and completed (for this season, anyway.)

Update: I later needed access to the greenhouse wall studs to hang shelves on this wall. It was tricky to work through the foam insulation to do so, but possible. We were able to locate the wall studs and cut small holes to insert long T-bolts into the channel. Then we installed 1 x 6 boards to equalize the pressure on the foam over a larger area, and we attached the shelves to those boards. Not easy, but I don't think trying to fit this foam insulation around shelves would have been easy either.

One more note about this foil-faced insulation. The foil acts as a radiant barrier, and I've read you defeat the purpose of this barrier if you put anything directly on top of the foil (touching it.) I'm not in love with the look, as I've said, but I've determined that I could cover it with another material if I used some sort of spacers to preserve the air space in front of the foil. If I find the reflective surface increases temperatures in the summer (yet to be determined) I could simply hang a fabric drape in front of it, removing it for winter when I'll probably enjoy the light it reflects back into the greenhouse.


Electrical Outlets

We added three GFCI (ground fault circuit interrupter) outlets, because they’re recommended for greenhouse use.

Outlet location is tricky. I knew I didn't want them too low so I'd have to crawl under benches to reach them, but if you put them too high you have to be careful about the length of your electric heater cords (assuming your electric heater sits on the ground like mine.)

Also, I accidentally had one outlet installed against a panel that was later replaced with a screen, which potentially exposes the outlet to rain. That outlet will now have to live in a plastic bag when the screen is in place. Moral: think ahead as much as possible!

We installed in-use outlet covers; these have a hinged lid, and an opening for the cords to pass through, so the outlet is protected from water even while being used. I wondered if the in-use covers were necessary in a greenhouse full of cacti (no misting or spraying in my plans) but then I realized my plans to add screens would allow rain in the greenhouse. Also, one of my outlets ended up under a shelf of plants, and the outlet cover ensures that no water splashes from watering my plants will end up in that outlet.

The only problem I've encountered with these in-use outlet covers is that they will only close over normal standard plugs. I didn't plan on using anything else, but I later bought thermostats that utilize a piggy-back plug system (the heater plug goes in the back of the thermostat plug, which results in a very long combined plug!) As a result, the covers won't close, as shown to the right. That's something to keep in mind.

¾” PVC conduit was used to protect the wiring. The conduit was attached at the ground level by screwing into the wood of the foundation. We secured it above by putting screws into some of the horizontal wall braces.


Aluminet Shade Cloth Screen Panels
The soaring temps in the new greenhouse (130° with the doors and roof vents open) told me I’d be needing shadecloth (and more) to lower the heat.

I ordered Aluminet reflective shadecloth from IGC. It comes in different densities, and I chose 40%. I agonized over the choice, but I read that 40% was used by several cactus and succulent greenhouses, and I was worried that a heavier density might block too much of the light my plants need. Time will tell.

(Update: Time did tell, and the strong summer sun proved too intense for the health of my plants. I kept the 40% Aluminet as an interior drape just inside my greenhouse roof, and added a second layer of 60% Aluminet to go on the outside of my roof. During most of the year, I need both layers. In addition, I'm sure adding the Aluminet to the outside of my roof has been helpful in extending the life of my (questionable) Harbor Freight polycarbonate panels.)

Aluminet is woven from tiny reflective fibers of high-density polyethylene. It stretches perpendicular to the lines in the fabric, and diagonally. It can tear on a sharp object, but tears can be sewn up by hand. It doesn’t unravel, and it’s very lightweight. I’ve read the fibers attract dust like a magnet, but it’s supposed to rinse right off. This article says that Aluminet comes either shiny on both sides, or double-sided with one shiny side and one colored side. Mine came with both sides shiny. I had several ideas for the Aluminet, so I ordered mine as raw fabric (no seamed edges or grommets.)

Some people make screen panels to replace the regular polycarbonate panels in hot weather. I wanted to try screens using Aluminet shade cloth as the fabric (for shade and air ventilation at the same time.) I used do-it-yourself window screen components (Home Depot or Lowes) as shown in the photo above. You cut the metal frame to length with a hack saw, and plug plastic corners into the ends. The fabric is attached with plastic spline pushed into the groove, using a spline tool.

I wanted to use the same spring glazing clips to secure the screen panels in the greenhouse frame, so I chose the thinner 5/16” screen bars (instead of 7/16”.)

Brace Tip: I had to build two cross braces into each panel frame. Without the cross braces, the stretchiness of the Aluminet bowed in the long sides of the frame …over 1” on each side. The cross braces are attached with small metal clips purchased separately. In my kits, they didn’t stay in place until I added the fabric and spline.

Measuring Tip: The plastic corners add ¾” to the length of each side, but my directions said to “subtract 1 ¾” from your desired length” to compensate for both corners. That didn’t make sense ( ¾” plus ¾” equals 1 ½”) but I followed the directions. Sure enough, my first screen was ¼” too short and ¼” too narrow to fit well. So, just determine the final screen length, subtract 1 ½” for the length added by the plastic corners, and cut the metal to size.

Density Tip: I now have Aluminet stretched in screens in some parts of my greenhouse, and draped loosely in other parts. The Aluminet installed in screens lets through a bit more sunlight, since the stretching opens the weave a bit. You might keep this in mind when deciding which density to order, if you're planning to use it in screens.

I cut the cloth so it was roughly 1” larger than the size of the screen frame.

The 40% Aluminet was easy to secure with .140 size spline. I’m sure higher densities of Aluminet are thicker, but this material is so soft I think they’d still work. If it seemed too thick to fit into the groove, you could try smaller spline.

I secured one long side first, top to bottom. Then I did the other long side, but this side involved pulling and securing a few inches at a time (stretchy stuff) so I started in the center and worked towards both ends. The top and bottom were last.

Aluminet has lines in the weave, and it stretches in the direction that’s perpendicular to the lines. In my screens the Aluminet lines ran vertically (the least stretchy way) but I think it would work in the other direction as well. It’s possible the cross braces wouldn’t be as critical if you installed the fabric so the most stretchy direction went lengthwise, instead of installing it like I did.

Also, Aluminet has a seam every 7 feet, and one of my panels includes the seam. It didn't cause any problems, so you don't need to design around the seams in the fabric.

I trimmed the excess fabric with scissors, leaving about ½” edge (thought it might pull out if I trimmed it close.) The photo to the right shows how it looks inside the greenhouse.

I attached the Aluminet panels with the same glazing clips that secure the polycarbonate panels.

When I made the screens, I was careful to position the cross braces so they would line up with the horizontal braces inside the greenhouse. I thought I might need to attach the screens to the braces with screws, using the same screw holes I use to attach the poly panels. However, I found the clips worked great by themselves.

Tip: I numbered each polycarbonate panel with a permanent marker before removing them. We didn't center the self-piercing screws carefully when we attached the panels, so now I have to put each panel back in the same place to make sure it lines up with the drilled hole in the horizontal braces.

Okay, two-thirds of my south greenhouse wall is now Aluminet panels. I love the clean appearance and the increased ventilation! Before installing these, the temperature in my greenhouse was at least 130° with the doors and all four vents open; with these panels in place, it’s closer to the outside temperature. Installing the roof shade cloth and exhaust fan should help even more.

I'm tickled pink with how these turned out!

Of course, summer rains will easily penetrate the screens, so I’m aware of what I put on that side of the greenhouse. Annually, we have lots of heat and little rain, so it should be a worthwhile trade-off for me. I’ve thought about a clear plastic curtain on the inside of the south wall to be pulled into place during heavy rains.

Here’s what happens when you don’t consider screen placement when doing your electrical. Although we used GFIC outlets and in-use outlet covers, I didn’t plan on the back of the outlet being exposed to rain. I’ll have to figure out how to weatherproof the back, or live with a baggie over that outlet in the summer. Darn.

When the fall night temps get too cool, I’ll remove the screens and replace the polycarbonate panels. I tried leaving the screens in and putting the poly panels on top, but the combined thickness of the two layers won’t allow the glazing clips to fit in the channels.

Later I discovered I could put the polycarbonate panel back in place, with clips and screws as usual, for protection from cool night temps. And, if I still need a bit of shade for a while longer in the season, I can put the screens back on TOP of the poly panel, and I can make them stay in place by inserting clips into the gap backwards (photo soon.) Yes, it looks odd, but hey, it works. After I get a bit deeper into the winter season, I'll take the screens off again so I can have all the sun possible.

The cost for each 6 ½’ tall frame was about $12 (not including the cost of the Aluminet.) Of course, once you have the screens, you'd be able to swap out the Aluminet for different densities, or even replace it with regular screen material, bird netting, or whatever you wanted to be creative with.

Adding an Exhaust Fan

We used this fan calculator to determine that our greenhouse would require a fan capable of exchanging roughly 1500 CFM (cubic feet per minute.) I ordered a 16” three-speed louvered exhaust fan from ACF Greenhouses. The three speeds are capable of 2950, 2050, and 1200 CFM, so at the highest setting it should exchange the air in the greenhouse about every 30 seconds. I wanted at least one air exchange per minute, so I’m glad to have the extra cooling capacity.

Normally people install an exhaust fan in one side of the greenhouse, and a shuttered vent in the opposite side, so there's a way to let air in (the vent) and a way to pull air out (the fan.) We're going to try using screen doors instead of the shuttered vent for air intake, so we only ordered the fan.

We installed the fan in the high part of the back wall. First we removed the Rear Center Panel (part 57.)

One of the modifications we made to the back wall was the addition of a ½” x ½” aluminum angle (so we could screw the upper polycarbonate panels to something for strength in winds.) Now, we had to cut part of the brace away to install the fan.

This is called Lack of Planning.

The fan came prewired with a 9’ cord, and four mounting holes (two on the top, two on the bottom.)

We bought a 4’ length of 1/8” thick 1” x 1” aluminum angle from Lowe’s, and cut it in half.

We drilled four holes in each piece of aluminum angle; the two center holes were used to bolt the angle to the fan.

Here’s the fan in place, attached by putting bolts into the track and through the holes we drilled in each end of the aluminum angle.

Putting this in place and securing the four bolts is one of those times when four hands are a lot better than two.

Yes, that sky is getting threatening. (The best way to get it to rain in the desert is to start a project that is best accomplished dry.)

Time to cut the hole in the polycarbonate panel. No pressure; just ignore the rumbling thunderstorm approaching.

I measured the outside part of the fan, and the space on each side of the fan, and marked the hole on the panel using a permanent black marker.

The poly was actually much easier to cut than I thought it would be, making several passes with a good sharp box knife and a metal straightedge on cardboard. Phew.

The completed panel ready to be reinstalled, with the hole to fit over the outside portion of the exhaust fan.

I won't be afraid to cut more holes in my polycarbonate panels if I need's quite easy.

Here’s the panel reinstalled over the fan.

I later caulked around all four sides of the fan with clear silicone caulk, to keep rain and cold air out. I'll have to build some sort of cold weather cover for the fan for the coldest part of the winter...I can see small gaps between the louvers.

Is that a black sky or what?

The installed fan from inside the greenhouse. It works! At the highest speed it's noiser than I'd like, but I'm getting used to it.

Without this fan I wouldn't be able to keep plants in the greenhouse year round...our summers would be far too hot. With this fan in place, as well as some additional small fans for HAF (Horizontal Air Flow), and generous amounts of shade cloth, I'll have a fighting chance.

It never rained a drop. All that bluster and no moisture. Welcome to the desert!


Adding Thermostats

I needed a way to have my heaters and exhaust fan turn on and off automatically, depending on temperature. I purchased thermostats from Their price was good and their shipping was lightning fast.

I needed three thermostats (one for the exhaust fan, and one for each of my two 1500w electric heaters.)

Some thermostats are designed to be wired directly into the heating or cooling appliance, but this pre-wired portable thermostat plugs into the wall outlet. The fan (or heater) plugs into the back of the thermostat plug.

The thermostats from come wired to use with heating appliances. To use it with a fan, you make a simple adjustment inside (moving two wires) as explained in directions they send with the thermostat.

The location of your thermostats affects how often the fans or heaters will kick on. If the thermostats are located in full hot sun (or right in front of a heater) they won’t give an accurate reading of the real temperatures in the greenhouse.

Some people build small wooden boxes, painted white, to shield the thermostats from sun. These can be open on the front and bottom, and solid on the back, top and sides. I’ve even seen pics of vented thermostat boxes that were cooled by tiny fans installed in the box. (That's not gonna happen.)

I bought an unfinished slatted craft box at Hobby Lobby. I pulled the slats off the bottom, and pulled one off on the top, to make room for my three thermostats. I used a dremel tool to make the cut outs for the tops of the thermostats, and I painted it white.

Then I covered the outside of the box with a few layers of scraps of Aluminet shadecloth, secured with aluminum tape. (A further continuation of my favorite Nasa space shuttle decorating scheme.)

My hope is the slats and fabric will allow air to pass through for ventilation, and the shiny Aluminet surface will also reflect sun away. I'm really not sure this will provide enough shade for the thermostats...we'll see.

I tried keeping the thermostats in the shade under my benches. This worked well, but I knew it would only be a matter of time before I accidentally poured water on them while happily watering plants.

I decided I needed them in one location, protected from sun, centrally located, with good air flow, roughly at plant level, and where they wouldn’t hit me in the head. I spent a lot of time staring at my small greenhouse, trying to find a spot that would work. I finally hung the box from the EMT braces we installed at the top of the walls, over a bench. The back of the box faces the sunny south wall, and the open front faces the north wall.

Visually, it's not the lovliest addition to the greenhouse, but if it will keep my heating and cooling systems working well, and keep my plants happy, I'll put up with it. It's annoyingly visible, but it's easy for me to access, and it's out of the way of plant tending.

To get all the thermostats to the center of the greenhouse (from various outlets on different walls) I ordered them with 20’ cords, instead of the usual 8’ cords. This cost me about $5 extra per thermostat.

photos soon...


wenders said...

Hello Mudhouse,
In case the lack of comments has deflated your interest in sharing these amazing experiences, buck up. I have just started looking around for some kind of greenhouse set-up, live in NM, outside Santa Fe, deal with the same kinds of winds, snow in October (gotcha), hail in July (double gotcha). DO NOT want to succumb to shopping at Whole Foods; prices a little to rich, folks a little too snooty. Hence the return to EARTH.
How is your assembly doing? What have you planted? How is it going?
Thank you for your excellent instructions; I think you may have a future in competition with whoever Harbor Freight is (especially if they are Chinese).
Please post more.
Thank you.

mudhouse said...

Hello wenders,
Thank you for your kind words. I'm shamefully behind in updating our progress, and I will remedy that soon. As of last week, the greenhouse has been filled with my collection of cacti and other succulents, and I am happy to report that everyone has survived the first night requiring a heater. Phew.

The Harbor Freight greenhouse has remained quite sturdy in our New Mexico winds so far, although I do get annoyed by how loudly the roof vents rattle in gusty winds. I know of folks who use these HF greenhouses in areas with snow, and I think (in my newbie opinion) it would take pretty large hail to damage the polycarbonate panels. A number of my plants have permanent tattoes from small hail during our last monsoon season, but that was just before the greenhouse was up, so I have yet to see that first hand!

I will update as soon as I can stop fiddling with thermometers and heater thermostats. ;-)

The sky photos in your blog are absolutely lovely, as is your wonderful poetry. Thank you for posting them.

Peyton said...

Greetings from Louisiana,

Just a short note to say "Thank you" for this blog. I'll be putting up two of these greenhouses soon, and I have already learned a lot from a partial reading of your greenhouse building diary...
I appreciate your great documentation with photos.

Thanks & regards,


mudhouse said...

Thanks so much Peyton, I'm really pleased you found it helpful! Best of luck to you as you work on your new greenhouse.

Paul said...


Thanks so much for posting your experiences with this greenhouse. Very informative!

Good groing,

mudhouse said...

Paul, you are quite welcome! Good luck with your growing too.

wyndyacre said...

Hi Mudhouse,
Have enjoyed your account of building your HFGH. You have made some sensible and creative adjustments to what has been a frightening endeavor for some. I'm sure that many people will find your excellent instructions very helpful in building their own GH and you have ended up with a beautiful setup!

mudhouse said...

Hi wyndyacre, I missed your nice comment here, sorry to be so late in replying. You're very kind, and right on target about my motivation...I hope some of this will help the process be more fun and less stressful for folks who decide to tackle it. Fun is the whole point! Happy New Year,

Moraga said...

We just finished putting up the HFGH, which would have been even MORE frustating without your documentation and images. I added diagonal braces from the front and back wall to the sides using half inch conduit. We will be using it for starting tomato and chili seedlings for our pesticide free farm here in Los Ranchos de Albuquerque. Thanks for your contributions!

mudhouse said...

Hello moraga, thanks so much for taking the time to leave a comment, and for your nice words. The diagonal braces sound good (never too much bracing in NM winds.) I'm glad the photos helped, and best of luck with the tomatoes and chili!

Scott said...

Wow! I'm impressed with the effort you've made to improve the dismal instructions from HF. Great job! I had been thinking about getting a 10 x 12 to grow live coral for the saltwater reef tank hobbists. I now grow a lot inside. Now I can clearly see how it goes together with some very nice modifications. I have found a 300 gal. resin farm stock tank (for water for cattle) and that 2 will fit inside the HFGH. In my reading, I have learned that a large body of water is what can keep the temp. inside the GH and the corals inside the water at the proper temp. over the winter. With 600 gals. of water, it should be hard for the mild winters in Oregon (zone 8b) to change the temp. of the water very much overnight. I'm hoping the consitently overcast stretches of days in the winter will still provide enough warmth to keep the GH and water warm enough for the corals to least until the sun comes out again. LOL I'll have heaters in the water so we'll see. I've read that there is no comparision to how great corals look grown in sunlight vs. under metal halide lighting. Of course we've all seen what they look like in the underwater specials on the Discovery channel, so I am anxious to see what dazzling colored corals I can grow. Your efforts are an inspiration for me to start my project, even though it is to grow an underwater garden vs. the above water variety.
Thanks for all of your help. (:^) I'll try to let you know how my version of growing in a GH works out. Looking forward to more of your posts....

mudhouse said...

Hi Scott, what a fascinating use for a greenhouse! I can only imagine how beautiful that space would be. I know there are at least a few folks who post in the greenhouse forum at GardenWeb (link in the first part of my blog) that use their greenhouses for fish tanks instead of plants. I hope you'll wander in there and post some pictures; they might be able to offer help with your your unique project, and I could see your pictures there. (Did I mention you could post pictures? Don't forget the pictures!) :-)

Isn't in interesting how diverse a simple structure can be...chili peppers in Albuquerque, my own plants from arid places around the world, or an underwater garden of coral. How cool is that? Best of luck, it sounds great!

twopalmtrees said...

Hey Mudhouse,

Thanks for the blog! There was just so much useful information in here. I can honestly say that it saved me from numerous errors in building my own HFGH (although I did make a few new ones!).

I started construction with both the original user manual from HF and your blog printed off and I ended up with some well-worn, dog-eared papers covered in scribbles and comments and a cheap, but now robustly re-inforced greenhouse that has just survived its first storm!

Many, many thanks


mudhouse said...

Howdy Eurotrash,
Glad some of this helped. Making a few new mistakes in the building process just proves you are a creative thinker (good for you.)

You should see my HF manual...notes/pics from the GardenWeb greenhouse forum stapled everywhere, scrawled comments (some not very nice), question marks, dirt from being stepped on, and a few crinkles from exasperated flings into the air. But it got us through, huh?

Congratulations and happy growing! Sheri

Gary said...

Hi Mudhouse,

You should write instructional manuals! Yours is excellent! Thanks for the info and insights. I am like many others on a budget and have tried the polyethylene type greenhouses and have fair experience with a 6x12 made by Weatherguard. They seem to last for about 4 years then between the effects of the sun and our high winds here in Casper, Wyoming (45 mph plus winds with 75 to 80 mph gusts) which occur mostly during the winter and spring months, will shred in a few hours. I really want to go with something like polycarb panels that will last longer but most gh kits are costly for anything larger than 6x8 or the materials can also be costly. The HFGH 10x12 would be a nice size but again I worry about the winds even after the mods you and Gardenerwantabe show should be made. Many on the Gardenweb forums talk about high winds they experience but usually during a storm which doesn't usually last 24 to 72 hours like some of ours do each windy season. You said it is windy in NM where you live but are they as extreme as I have indicated for Wyoming? If so, then I am "sold" on trying a HFGH with the many mods to be made and will order one while I can still buy it for $599 in my current catalog. I really would appreciate you honest opinion. BTW you have meticulously constructed a nice setup and really enjoyed your blog.

Thanks so very much,

mudhouse said...

Hello Gary, and thanks very much! I understand your concern, but I’m hesitant to try to compare the winds in my area to yours. We don’t currently have a way to measure the actual wind speeds on our greenhouse (maybe someday.) I know that even if a local weather station reports "gusts to 50 mph" that doesn’t necessarily reflect the true wind speed on any single property.

We do have periods (usually in spring, or during our summer monsoon season) when the wind can blow for several days straight (no fun.) However, I regret that I can't quote specific wind speeds.

I’d agree that rigid polycarbonate panels would be better in winds, since I would think the wear and tear on the polyethylene results from the inevitable flapping or up-and-down movement of the flexible plastic in a big wind. With the screwed-in poly panels, the concern then switches to the force of the wind on the flat walls.

From my reading, these structures have failed in big winds when the first panel is lost; once the wind enters the structure, more panels are blown out, the frame can bend, and so on. We think our firmly anchored foundation, and firmly screwed down panels will withstand very strong winds, but I don’t know how to put a number on the wind speed.

We get our strongest winds from the north and west. For this reason, we placed our greenhouse so it’s blocked on the north by our house. I still get full west winds on the doors, which is not ideal, but I find that my ugly but efficient clamp keeps the doors closed tightly in any wind.

On very windy (but sunny) winter days a strong west wind can be a worry; I need the doors open for ventilation (no screens are open yet since the nights are too cold.) I don’t like to have big gusts going in the doors all day long, but frankly, it hasn’t hurt anything so just makes me uncomfortable!

I've been trying to use open doors as my air intake for my exhaust fan. This is a bit unconventional, but it seems to work fine as long as you can open the doors. I may eventually add some louvered air intakes so I can close the doors against the wind when necessary, and still have an air intake opposite my fan. I’m just mentioning this so you can consider door placement as you contemplate wind. On really windy days, I'm aware that it would be better if the winds didn’t blow right on my doors.

Another idea might be to post a thread on the GardenWeb greenhouse forum, and ask if any other HFGH owners have been able to monitor actual wind speeds...maybe other folks can provide more specific info for you. Hope this helps!

masscactus said...

Happy St. Paddy's day, Sherri and all.
I have a question about possible corrosion on my new, unassembled HFGH 10x12. The gravel has arrived, the foundation timbers are in place, and I'm ready to build the greenhouse. But, before I begin, I wonder if someone can enlighten me on potential electrical contact corrosion where the steel "L" brackets connect the EMT to the frame, where the hold-downs meet the steel base, and where the studs also meet the base. Should I somehow insulate (with rubber?) these contact points? is there actually a problem at these spots?

Thanks so much.
masscactus - ready to build

mudhouse said...

Hi masscactus,
In my reading about HFGH's on several internet forums, I haven't seen any reporting of this corrosion as a problem, but we do agree it's a possibility. The 10x12 HFGH has only been available for several years, but so far I don't recall seeing this mentioned as a problem for the 6x8 size either, which has been out longer. (Of course, just because I haven't stumbled across the mention doesn't mean it's not happening to anyone.)

Our extremely dry environment probably helps us in this regard, and you may have differing experiences in your wetter climate. One idea would be to do a post in the greenhouse forum at GardenWeb, because many folks there own HFGHs in much wetter climates than mine, and you might get a more accurate prediction of what to expect. If you do that, I'd be sure to include the words "contact corrosion" in the title, since it's a issue that might affect owners of many makes of aluminum-frame greenhouses, not just the Harbor Freights.

I remember you asked a question about snow load in another forum, and since then there have been some posts at GardenWeb about this question. One 10x12 HFGH owner reported a partial roof failure in January after about 10" of accumulation, and he plans to build a support for the center of the roof studs as a result. If you send me an email (either through GardenWeb's system, or through the other forum you've visited previously) I can send you links to the pertinent threads. I should post some info on snow load questions in my blog, but haven't had the time to tackle it yet. I don't get much practice with snow load here in the desert, but I could at least share what others have mentioned. Stay in touch!
Sheri (mudhouse)

masscactus said...

Hi Sheri,

Thanks for the quick response. I had a bit of a problem accessing the Garden Web forums recently, but their tech staff straightened me out and I finally did manage to post my question there. Pretty much the same question I sent directly to you. I'm looking forward to hearing back on solutions to the possible corrosion problem.

I have been following along on the "snow load" discussion and have decided to build an internal frame to distribute as much weight as possible into the ground. The idea is to make it both work, and look good. I'll probably work on it in the fall and I'll keep you posted on my progress. In addition to the internal framework, I'll employ my trusty roof rake. I think that should take care of the snow.

You should know that I printed out your entire "Field Manual." It's fabulous, and I'll be using it right alongside the HF manual. Thanks for putting it together.


chrishall1956 said...

Thank you thank you thank you!!!! With out your amazing pictures and tutorial I would still be on page 2. You have done a wonderful service for all of us.

mudhouse said...

Chrishall1956, thanks very much. I'm so glad some of it was helpful to you, and best of luck with your new greenhouse!

Laserfan said...

Hey mudhouse, just a note to say I've not seen your blog in a long while--great job! But especially you've done a wonderful job building and outfitting your HFGH. Very classy indeed. See you "around"! ;-)

Web4Deb said...

Hi Mudhouse. Your blog on building the 10x12 is excellent. I built the same one this spring and have posted some of my modifications to a blog.

Click for Blog

Keep up the good work!

-Rob T

rls1950 said...

What a wonderful blog. Thank you.

rls1950 said...

Have the thermostats performed well.

mudhouse said...

Hello rls1950, and thanks for your kind words. Yes, the thermostats have performed perfectly, for both the exhaust fan and my two heaters. No problems whatsoever!

heliconialover said...

Hello Mudhouse,
THANK YOU so much for the FANTASTIC instructions for the HF greenhouse! We just completed ours (just hours before a blizzard hit), and I can't imagine how it would have held up had we not used your ideas! We live in eastern WA, and get some NASTY windstorms up here.
Have you ever had any problem with your doors freezing up? It has been a major problem with ours. I have tried using window deicer in the lower tracks, but, at 7 degrees, it doesn't seem to do much. We clear the tracks out, and the doors off everytime we go into the greenhouse, but low and behold, the next time out, it's frozen up solid again. I am afraid this constant ice issue is going to destroy the doors. Got any ideas?
Thanks again, and please continue to post!

mudhouse said...

Hello heliconialover,
I'm so glad the blog was helpful. The problem you mention with the doors freezing shut has been discussed on the Gardenweb greenhouse forum as well; it seems to be a recurring problem for some folks in cold climates.

Some folks have eventually replaced the sliding doors with a hinged storm door to eliminate this problem. I've just updated the last part of Section Four, Adding The Doors, with some links to a few threads in that forum. You might find some of the photos in those threads helpful if this problem persists.

I sure wish I had a better solution for you (sand deposits are usually what cause my doors to bog down, instead of ice.) If you do discover something helpful, you might post it on the Gardenweb forum, since you'd probably be helping others in cold climates. Congratulations on the new greenhouse!

Stormsteed said...

Hello Mudhouse,
Your writeup is exceptional and inspirational, thank you.

I was curious to know if you had considered using a solar powered fan when you selected your fan. If yes, why did you eventually not choose that? If no, do you think this would be a feasible choice?

Thank you,

mudhouse said...

Howdy Storm,
Posts in the Greenhouse forum at indicate that the solar fan sold by Harbor Freight doesn't move enough air to sufficiently cool a 10x12 greenhouse. Folks calculate it would take four of them to cool the HFGH 10x12, so it's not very practical.

Here's a March 2008 post from cuestaroble, a very helpful GardenWeb greenhouse forum contributor:
"For a 10X12 greenhouse, you need to provide about 1000 cfm to adequately ventilate. You can subtract the ventilation provided by the passive bottom/top vents to arrive at the figure needed for a solar exhaust fan. The Harbor Freight model that I found provides about 250 cfm, at a cost of $200 plus shipping. This is close to one dollar per cfm. This would provide less than 25% of the needed total ventilation of the greenhouse. Other commercial solar models provide about 2 cfm per dollar. A 1000 cfm costs about $550, 1250 cfm, $650. If you want to look at more reasonably sized vent fans, at more reasonable prices, just search for "solar attic fans".

(Me again) For more good info, you can enter "HFGH solar fan" into the search box at GardenWeb.

Fortunately, my GH is close to electricity, and I planned on electric heating as well, so going with an electric fan was by far the most cost effective method. Hope this helps!

Stewart_Green_Energy said...

I really want to thank you for the work you put into this blog and the fact that you keep up with it. I am going to add my experiences with it as soo as I am doen putting mine up.

I was on ebay today and found this. 220357459199 This looks alot like your greenhouse, is it? If it is does the person have rights to use your picture? I have had my pictures stolen and used on the net before is why I ask.


mudhouse said...

Hello Keith,
Thanks so much for alerting me. You're correct, that eBay seller is using a photo from this blog, without my permission. I've contacted the seller, and I really appreciate the heads-up.

I'm glad the blog has helped! I hope you will post back with your helps everyone when we share our experiences. Good luck with your build!

tcmiv said...


Thanks for the excellent guide. Did you pre-drill the panels for the self piercing screws or just pierce them?

Thanks again,


mudhouse said...

Hi Ted,
If memory serves me, we predrilled holes in the first polycarbonate panels we installed, because we were concerned about cracking the panel. We then worked up our courage, and found we could use the self-piercing screws without predrilling holes. The new polycarbonate panels are more pliable than we thought, and we had no problems with cracks or splitting.

It also helps that the aluminum braces have such thin walls; the self piercing screws went right through with no trouble.

Now that my polycarbonate panels have baked in the intense New Mexico sun for several years, they have become slightly yellow and more brittle, and I’d definitely predrill before attempting to insert a screw. This brittleness has become most apparent on the panels that get full sun exposure without shadecloth protection, and this may not be a problem for folks in other climates.

SomervilleTx said...

Im so excited and thankful that I found this site. Thank you in advance for taking the time to post all this helpful information. I just today purchased this 10x12 greenhouse and for a really great price!! Onsale here in College Station Tx for $649...PLUS they allowed me to use a 20% OFF coupon that I printed from this web site:

Le said...

We've just put in our first two panels. It got too cold for the insulation to stick to the studs, so we had to quit for the night. Looks as if we will not get the greenhouse completed before Christmas as things are going (I work 12-hour days, six days a week).

We are eventually going to put the greenhouse over a 4 ft wide, by 4 ft deep fish tank, dug into the ground (immediately inside the door — a bridge will allow access without a standing broad jump) with a 2 ft deep, concrete foundation. We'll also have about nine female rabbits and their mate below the plants which we hope will supply some heat in the winter as well as their meat.

We wanted a temporary foundation so we could use the greenhouse this winter. because our early start tomatoes were so wonderful this past summer. (I get carried away, but on this blog, it's obvious I don't have to "sell" greenhousing.)

We dug a four-square trench, level bottom, about 12 in wide (depth varied from a couple of inches to the full depth of the metal foundation).

I took six 2x6x10 and six 2x6x12, pressure treated boards and cut them to the required lengths. These lengths are roughly (four of each of these) 9'11" and 10'9" and (two of each of these) 8'11" and 11'11". The longer dimensions in each case are the inside length of the foundation. The shorter lengths are the inside dimension minus twice the width of a (nominal) 2x6.

Then, for the longest "10 ft" and shortest "12 foot" boards, I cut a kerf, 3/4 in deep, and one inch from one edge of the board the full length. On the "10 foot" boards, I added an additional kerf on each end (same dimensions).

For each dimension, I also notched two of the "kerfed" boards to accept the stud tie-down brackets without crushing or distorting them.

Then came the fun. I put one of the unnotched "kerfed" 10 ft boards (kerf side down) so the grove fit into the "lips" on the lower edge of the foundation along its length and on both ends. Then I did the same thing with a 12 foot board on each side.

At this point, I had the whole foundation "inscribed" with the 2x6s, the ten-foot boards ran from one side of the foundation to the other and the twelve-foot pieces running between the ten-footers.

Using the notched boards, I followed this with doing the same thing for the upper edges of the foundation (using scraps of 2x to hold them temporarily in place).

The next piece of the puzzle was to force the longer "12 ft" boards between the "10-ft" pieces on each end and the two 12-ft sections that were already in place on each side. A mighty slam with a ten-pound sledge did the trick. (Well, okeh, it was several such blows, but it worked.)

The nearly last step was to put the shorter 10 ft pieces in place, using the same technique.

I then pre-drilled a hole about 2" from the inside edge of the sills in each corner and at the base of each stud. I then drove in a 5" lag screw to secure the boards to each other. (I used clamps to insure the boards were fully in contact with each other and to be sure that there was no warping as the screws pushed the lower boards apart before grabbing them.) I also used 4" screws to hold the "loose" ends of the top "12 ft" boards to the middle layer of the sandwich.

To keep the greenhouse firmly pied-à-terre, I used a "Dog Auger" (animal tether tie downs) in each corner with a short piece of 3/8" rebar that I ran through the "handle" and across the corners of the new wooden foundation. Of course, we're backfilling, as well.

This adds about 200 pounds to the weight of the greenhouse. It also gave me a good place to attach put the eye screws for cables holding the turnbuckles we're using to keep the greenhouse square when we move it next year onto the permanent foundation.

Freezing, Le

josh said...

Well, I've just about completed my 10x12 thanks mainly to you! One question though, I am planning to insulate my north wall the same as you and was wondering what would happen if I took the north panels and doubled them up on the front? would that increase my zone and can you see any value/harm in doing this?

Thanks again for the incredible help! I did this by myself and simply could not have without you. - Josh

mudhouse said...

Hello Le, sounds like you're well on the way to a nice set up! Your temporary foundation sounds great, and also a lot to accomplish with freezing temps nearby. I have read about folks who have successfully constructed their HFGH in one location, and moved it on top of a permanent foundation later. I'm sure you're aware, if the panels are in place when you move it next year, you're basically moving a giant box kite...beware of any breezes working against you!

Glad to hear you've made such good progress, and best of luck!

mudhouse said...

Hello Josh, glad some of this has helped!

I have read that much more heat is actually lost through the roof of a greenhouse than is lost through the walls or floor, so I don't think doubling up the poly on the opposing wall would actually make much of a difference in retaining heat. (In fact, in colder climates, many folks extend the foil-faced insulation I used on my north wall at least partway up the northern roof slope as well, to help prevent some of the heat loss through the roof.)

Also, we think the poly panels are pretty important to have in place in the north wall, behind the insulation, unless you fabricated some other strong panel material to use in their place. Although the poly panels won't be able to transmit light when covered with insulation, they do stiffen that wall, adding strength to the structure. With foam weatherstripping tape around the edges, they provide a pretty good seal to help keep that precious warmed air inside your greenhouse.

So, our take would be to use the poly panels on the north wall as per the kit, but perhaps someone else will chime in here with other observations or ideas as well.

Le said...

Actually, moving the thing with the panels in place is not in the cards. We do this ourselves, so it's just too heavy. We'll simply remove the panels (and the doors), tie a rope to the temporary foundation, lift it onto the new one, and then start anchoring it in place with J-bolts in the concrete.

We haven't been able to make much progress over the past few weeks because of the intense cold and 18" of snow.

A neighbor is helping build some trusses that we'll weld to the cross braces at the top of each stud (I believe you only installed three — we wanted five because we've seen at least two three-to-four foot snowfalls in our back yard in the past three years; thank goodness for global warming, or they'd have been nine feet deep, I'm sure). They will attach to the center of the braces in a "V", then have an additional cross brace from rafter to rafter. He can weld EMT, a skill I lack.

I used a piece of the original carton as a template so we didn't have to stand on a couple of ladders to make the measurements, especially the angles.

We'll let you all know how they work.

Still cold, but not freezing this week, Le

Ed said...

Today, Oct 15, 2010 I finally finsihed this greenhouse. Took about a day and half. Foundation and sides yesterday. Rest of sides (supports), roof and glazing today. Directions have changed some. No longer is it stating to build roof on ground, they piece it together like the author did here. Back is still a pain in the ass. I put mine on 4x4 posts and achored to the posts. Regular screws go right through with some pressure, no need for self tapping. Be sure to read the directions, they were not that bad when you paid attention to them. Be sure to follow the arrows or things won't line up. Made that mistake once. The glazing clip God must have shined down on me. I got two large bags plus some extras. I was able to put 10 clips on the the large roof sections, 6 on the smaller. 8 on the sides and front sections as well as others. I could probably use another dozen or so but I am going to caulk the sides and roof in. Doors are another story, hard to glide so I will play with them another day. Best to put them together in the house on a large empty spot on the floor rather than outsides. Only use one screw per section until you get the door together then once all ok then go back and tighten and add extra screws. Also, hand tighten the nuts/bolts to the GH, you might need to shift it to get thing right. Be sure to check squareness and plumb. I was lucky, mine came ups pretty much square from the get go. Guess the Sqaurness God was looking down.

mudhouse said...

Hello Ed, congratulations on your greenhouse, and thanks for your post. I suspect your care in construction may have had more to do with your nice squareness than luck (it's easy to get this flexible frame out of square.) Good job.
Regarding the doors not sliding well, I have one tip that helped my doors slide better, involving adding a small shim at the top of the door frame. I have an explanation of this, and some photos, in this thread on the GardenWeb greenhouse forum. I haven't taken the time to add this to my blog here, so for now, try just clicking on this link. Maybe it will help.
Sticky Doors on the Harbor Freight 10x12 Greenhouse

Ed said...

Update on the doors... I used WD40 and the doors glide with ease now. I also have seen pics posted with these bent in half from wind. I added 5 cross bars for extra support adn I am running two from the back to the front. All using L brackets to the attached bolts/nuts. Where the EMT's meet they will be attached. Feel this will give the extra support in high winds and this can be done for about $50.00

Dave said...

Dear "MudHouse":

I cannot THANK YOU ENOUGH for taking the time to post such AWESOME information. The HF greenhouse is again on sale, and I am trying to decide if I want to take on this massive project. If I do, I will be referencing you blog ALOT!! Thank you VERY MUCH... -Dave, Colorado

mudhouse said...

You're very welcome Dave. My greenhouse brings me a lot of happiness, and if you decide to build one, I hope yours does too.

jd said...

Hello Mudhouse:
When you began your greenhouse and your informational postings in 2007 I don't imagine that you expected to find grateful readers four years later. Yet here we are. I think your comment that the HF GH is a great starting point for a finished GH is right on the mark. For just a few dollars more and the kind of ingenuity that you and others have shown, you can have a sturdy and workable structure for an extremely competitive price. You just have to approach it the way you would a crossword puzzle. Sometimes the Sunday puzzle takes more than one day to solve, and similarly, the HF GH takes more than one day to build.

mudhouse said...

Hello jd, and thanks for your very kind words. I agree; I tend to see growing stuff (with or without a greenhouse) as an ongoing and eternal process anyway...emphasis on the word process. We never really worried about putting up our greenhouse in a hurry, since each step was another lesson in learning how the structure worked, and it gave me time to think about how it might best work for the particular plants I had in mind. It's all a learning process, and that continues to this day. Hopefully, it always will, since that's the fun of it, for me.

My little HFGH and two 1500 watt heaters just got hundreds of my succulents through the coldest weather here in Las Cruces in about 40 years (-6.5F) I can't say I want to repeat the experience (too cold for me, and the sliding doors did freeze shut for about 18 hours.) However, it's reinforced my feelings that the rather humble HF can be a great way to learn about greenhousing without breaking the bank. It can be a good stepping stone in seeing where gardening can take you, and whether or not it makes you happy. It sure works for me.

Richard Leon said...

We have 5 chain link 6x14 dog kennels on a concrete slab. in 2004 three hurricanes in Central Florida dropped an oak on the first two. I bought a HFGH the next year intending to place it there. Then Wilma struck and it has sat in the garage since. Reading your Blog has encourage me to get cracking and put it up. My luck, next year we will get another hurricane.

Out of curiosity how has it held up over the years? Panels? Did the base rust?

masscactus said...

Hi Richard,

This is Laurence in Massachusetts. I just want to wish you the best with your HFGH project. I built mine a couple of years ago, closely following the guidance of Sheri (Mudhouse). Whatever you do, take her advice - it is spot on.

To your question on how has it held up, let me say that it is doing just fine. No signs of rust, warping, or any other serious problems. So far my 10x12 greenhouse has survived winds over 60 mph, and 2 feet of heavy snow. Now I know snow won't be a problem for you, but wind surely will be. Therefore, I highly recommend that you brace the greenhouse all around, on the inside of course. In fact, the removable snow poles that I incorporated into the structure could possibly be made permanent in your greenhouse, attached at the roof and base. This would help to prevent "lift" in extraordinary winds. Even with the extra bracing, though, I doubt it will survive a full-blown hurricane!

If you'd like to see pictues of the bracing system I built into the green house go to

masscactus (Laurence)

Web4Deb said...

I am also happy with my HFGH I build a few years ago. I live in Connecticut and it did suffer a hit with the snow this year, but the extra bracing helped a lot. My blog about it (and other things) is at

mudhouse said...

Laurence, great to hear from you again! Your photos of the snow load bracing are extremely helpful, and that looks like a wonderful solution (nice that they are removable, too.) I the event of a hurricane, all bets are off! Hope your succulents are surviving the winter. This has been a very mean-spirited winter for succulent lovers in southern New Mexico.

Richard, I will echo Laurence's comments, we see no signs of rust on the base at all, no signs of warping or any problems with the frame at all.

My panels, however, have yellowed from sun exposure, and many panels unprotected by shadecloth have now developed multiple 1/8" size holes in the outer wall (about 4-10 holes per panel on the south and east sides.)

I mention the problem of premature Harbor Freight poly panel deterioration on the first page of this blog. From reading several online gardening forums, it seems to be a problem that only affects some Harbor Freight owners, and those with the most problems tend to be in hot climates with increased sun exposure. There may even be some manufacturing variability...? There is no warranty on the kit or the panels.

My panels will have lasted almost 4years in New Mexico sun when I replace them (this spring or summer.)

It's my educated guess/opinion that the HF panels do not actually have a true UV coating as other greenhouse-quality twinwall poly panels do. This would help explain the very reasonable price of the kit (quality twinwall poly with true UV protection is expensive.) If the panels did have the typical UV coating on one side, we'd be given instructions about which side of the panels to face out, but HF says it doesn't matter. Normally, twinwall poly panels are clearly marked as to which side has the UV protective coating, and it's critical that the coated side faces out. HF has been somewhat evasive when I've emailed them direct questions about the UV coating. I personally don't think it exists, but I haven't subjected any samples for laboratory testing. Some HF owners have posted about panel failures before reaching the two year mark, so I feel fortunate to have made it this long in my climate.

I have covered my panel holes with clear duct tape. I'll be replacing them all except for those on the north side. I won't use HF panels, since I now know they won't last very long here. It's a major hassle for me to unload my spiny greenhouse, as my plants are permanent residents, and not seasonal. I don't want to replace the panels again in 3-4 years, so I may order 4mm twinwall polycarbonate from a greenhouse supply company (very pricey...more than the cost of my HFGH kit.) I'm also considering 3.5mm Solexx, a translucent white twinwall product. That would cost a bit less, but I need to make sure the white panels admit enough light for my succulents.

However, even with this disappointing panel failure, I still recommend the HF greenhouse as an economical and practical entry into greenhousing. Per year, I'm frankly still money ahead, even after I buy new panels.

Using shadecloth on the roof and any walls subjected to intense sun seems to make quite a difference in the Harbor Freight panel life for those in challenging climates. I also know a HF owner in Florida, and she has not had any problems to date with her HF panels (she is adding her third to the two she has enjoyed for years, joining them together to form one long greenhouse!)

I wish you the best of luck, and hope you have many happy years with your greenhouse, as I've had.

mudhouse said...

Also, I should have re-emphasized, I still believe that reinforcements are absolutely critical to withstand winds. We adapted our methods from posts on the GardenWeb greenhouse forum, and others have gone on to find even more elegant ways to provide the necessary stiffening (as in the photo link kindly provided by masscactus.)

Without reinforcements, and screws in the panels, and extra panel clips, I doubt our greenhouse would still be standing. I believe we've also survived brief gusts in the 60mph range, and 40mph winds for more extended periods.

My goodness I am long-winded today myself...apologies!

mudhouse said...

For some reason, web4deb's link to his outstanding blog didn't post. Here it is:
web4deb's blog
Be sure to click on the links to see his outstanding videos in the blog. Remarkable!

wifi said...


I'd like to comment on the issues you had/have with the electrical system. I scanned all the comments and saw no other comment addressing that...if someone did, I apologize in advance. I offer it in the hope that someone who is contemplating a similar installation won't have to deal with the problem after the fact as you had to.

Use of steel boxes of the type you used will lead to eventual rusting and replacement. they are not rated for that kind of environment.

A far better way is to use PVC boxes (in fact everything PVC) since they are readily available at most home stores. This eliminates the issues related to rain also.

Gorgeous benches and the tile work is stunning...!


mudhouse said...

Wifi, my apologies for not replying to your good post sooner. You provide very good advice, and I thank you for pointing this out. We tend to get a little complacent here in the dry desert (our last decent rain, believe it or not, was in September, and it's now March.) Our little greenhouse has a lot lower humidity than most across the country, and others in kinder climates with more moisture would especially be wise to follow your advice. And, it would definately have been a great improvement over my awkward "baggie over the outlet" solution. Thanks again!

rockitman66 said...

Your inventive genius is unsurpassed. I have never seen such ceativity from the insulation and supports all the way to the sink mosaic counter-top and the vent fan. Your awesome, keep up the good work and thanks for sharing this extensive manual that took so much work.

Matt said...

I am getting ready to build my HFGH 10x12. I was wondering if there was anyone who omitted the flimsy steel base, and bolted the unit directly to a wood foundation?


mudhouse said...

Hello Matt,
This question came up in a Gardenweb forum thread recently, and you can read it here:
Harbor Freight Base Question

As I mentioned in the thread, my initial concern is the base is designed to accomodate the hold-down connectors (part 47) that do two things at the same time. They secure the aluminum floor plates (parts 1 - 6) to the steel base; and they also attach the vertical aluminum wall studs. So, after you bolt or screw the aluminum floor plates to the top of a wooden base, you'll have to figure out how to attach the vertical wall studs to the aluminum floor plates, with no hold-down connectors to help. The person in the thread above did find a way to do this.

I haven't had any problems at all with the base in the kit, even in our very bad winds here in southern NM, and I wouldn't hesitate to use the same base again if I built another HFGH. However, these kits do lend themselves to creative brainstorming, innovation, and adaptation, so I'd be the last one to say anything was impossible.

Robert said...

Hi Mudhouse,

Your exceptionally detailed descriptions and photos are a huge help in all aspects. Thank you for taking the time and effort to share your lessons learned and all the great modifications tothe greenhouse.

I already have a similar greenhouse from a different manufacturer, so I know some of the headaches and challenges ahead. I just purchased two of the HF greenhouses for additional wintering-over, and will be encorporating a great many of your suggestions.

I am contemplating mounting the base plates directly to a 3"x6" (or maybe 3"x12") wood frame and doing away with the steel frame that has rusted out on the previous greenhouse. I am thinking that I should be able to do all the attachments with angle plates to provide a secure mounting to the foundation.

My biggest installation / modification idea is to install the two greenhouses back to back, bolting them to each other, and modifying the end walls to provide for an interior walkway roughly the same size as the door opening at the other ends. I know I will have to cone up with spacers between the two greenhouses so that the framework does not bow / buckle, and I will need so figure out some sort of connecting filler on the external edges of the sides and roofs where the two greenhouses meet.

Might you have any thoughts as to the feasibility of turning two greenhouses into a single 10'x24' greenhouse with doors at both ends?


mudhouse said...

There are at least three or four members of the GardenWeb greenhouse forum that have posted about joining two Harbor Freight greenhouses (various sizes) together, end to end. Probably the most helpful thread is this one, showing how funnylady joined her two 10 by 12 HF greenhouses together, using metal wall studs where the two greenhouses meet:
Two HFGH 10x12 Greenhouses Joined Together

Here is a link to one of rosepedal's threads, showing some photos of their double 10x12 structure, near the end of the thread:
We're Going Saturday...

Here's a link to some photos shared by milwdave, another GardenWeb forum poster, when he joined two 6x8 Harbor Freight greenhouses together, back in 2005:
milwdave's photos

And finally, here's a thread posted by someone who also decided not to use the steel base included in the Harbor Freight kit. I was concerned this would be difficult, since the "Hold Down Connectors" that connect the vertical studs to the base are designed to grasp the lip of the steel base. But, they seemed to manage just fine without it: HFGH 10x12 base problem

For what it's worth, I really don't find comments about the HFGH base rusting out. Ours still looks great after 4 years. Of course, we do live in a dry climate, and we also mounted it to the top of a wooden foundation, as shown in the first part of this blog, instead of burying it in the ground.

Hope this info helps a bit. Best of luck with your build!

ek said...

Does anyone know the exact size of the lower panels? I'll be ordering a greenhouse and immediately converting the northern wall to rigid insulation. I'd like to use the polycarbonate panels to replace single pane glass in my sunroom and it'd be great to recycle the HF panels.

mudhouse said...

The wall panels (part 58) measure 1' 11" wide by 6' 5.5" long.

The parts list in the manual says the panels are 6' 5" long, but when I measure my actual wall panels, they're a half inch longer.

alicia said...

Thanks so much for this HF Greenhouse info! You saved my honey a lot of headaches and frustration. Could you tell me the dimensions of your sink/potting table? I definitely want to incorporate a sink and a bench as well. Thanks!

mudhouse said...

Hello Alicia,
Glad this blog was a little help. My potting bench measures a bit over 2' by 4'. The little sink is 15" square (commonly sold as a bar sink, I believe.) I've been happy with the size of the bench. I don't think I'd want it much larger in a 10x12 greenhouse, because I wouldn't want to give up any more bench space for plants. The little hole to sweep dirt into has worked out great. I'm not a very good housekeeper, and that has been a fast way to clear the table after messy potting up sessions.

By the way, it never looks as neat as it did in that photo, when it was all new...definately a work station, now! But it has held up well. There are a few scratches on the tiles from pot bottoms, but I don't mind.

Jay B said...

Thanks for posting all this great information. It was a great help in keeping our greenhouse in one piece in these New Mexico winds. So far it has stood up to 60mph wind gusts. However we did have an issue with the front doors bending in during that 60mph wind. The bowed and then bent about in the middle where they come together. So I made another enhancement that I thought I'd share.
Since it seemed of no real use, I removed the rubber flap on one side of each door. The one where the doors meet each other. This opened a channel running from top to bottom of the door 1/4 of an inch wide. I purchased from our local Home Depot a piece of aluminum ¼ thick, 1 inch wide and 96” long and cut it to the length of the door. I drilled holes in the edge of the door (into that ¼) channel at each horizontal brace and fitted the bar in to the channel and then marked the bar for pre-drilling. Using a drill press I predrilled holes in the ¼ thick side at each of the marks. Using the standard self tapping screws that have been used to attach the panels I attached the bar and the door. This provides a solid opening edge of the door.
I also ran two lightweight bars/angle that are attached to each of the horizontal braces and then the panels are screwed to them. The panels on our doors are simply set in grooves between the horizontal braces and the wind pushes them out so the brace on the inside just gives a place the put screws into and thus keep the panels in place.
I can provide pictures but didn’t see a place to post them here.

mudhouse said...

I'm glad the blog helped, Jay, and nice to hear from a fellow NM greenhouse owner. Clearly you understand why I tend to get a bit overly focused on wind protection!

I get strong winds directly on my doors too, especially in the spring. However, I'm not sure they've ever hit 60 mph, which probably explains why I haven't seen the bending you describe. Our house shelters our GH a bit from some of the heaviest winds. On bad spring days I use three heavy clamps to keep the doors closed tight (top, middle, bottom) and make sure I have some of my screen panels open on the south side for ventilation.

Your description sounds like a great way to strengthen the joint between the doors, and it might be helpful to others who are facing extreme winds directly on their GH doors. I don't think there is a way for people who leave comments to post photos here, but if you start a thread in the greenhouse forum at GardenWeb, I'll watch for your post there and post a link here back to that discussion, so folks who read here will have a direct link to your pictures.

I hope you enjoy your greenhouse. Watch out for those winds (forecasting 40mph today and tomorrow here, so spring must be coming.)

GumbyGrower said...

Hello, Thanks for taking the time to post all the tips for installing the GH. I only had room for the 6X8 (and it could not be seen over the fence... Dang home-owners association.)but it all helped with the smaller version... I was looking at the exhaust fans you recomend and ACF Greenhouses website liked your blog too! I reconized pictures of your awesome benches and a couple others they used. Look at Hopefully you know they used your stuff or at least get a good discount for it cause you deserve it!! Thanks again for making my GH installation go smooth!

mudhouse said...

Hello Tracy, I'm glad the blog was helpful with your 6'x8' greenhouse. You have sharp eyes! The good folks at ACF Greenhouses did contact me for permission to use my photos of the fan installation. I appreciated their courteous contact, and yours, since some people do use internet blog photos without contacting the owner. Thank you, and I hope you enjoy your new greenhouse!

Daywalker said...

Greenery Greetings to U Mudhouse ~
We picked up the 6x8 HFGH (240 after coupon)about a week or so ago. Read the reviews n tips n what have you, until my eyes bled! I am ever grateful for all the DIY'ers out there who have taken the time to share their HFGH experiences. With that said, I had to reach into your Blog and say thanks for the clarity and continuum of your GH adventures!

Except for installing the Crown, I have taken this project on solo and have made it all the way to the door installation as of last night. Here and there I stop and hit the web on steps that may have been an issue for others; modern day measure twice concept = hit the Web. *grin* I am picking up Alum tape today for the panels, etc...but the question I have is this:

As per noted in the HFGH instructions, I utilized the pressure treated wood as a base/sill ~ there was a sticker on the end of the lumber with teensy-weensy print that warns not to allow direct contact...with Aluminum. I was a bit perplexed since the frame is Alum and this is the type of wood 'req'd' by the folks who manufactur HFGH.

Before completing this project with the panels, there is still a window of opportunity to take measures to avoid issues related to the PT wood vs Alum. I did hit the boards with Thompsons water seal. My thoughts have me considering shooting a(spray)foam type of sealer between the wood and Alum and was wondering what your thoughts are on this?

Thanks Ahead!

Still Groovy After All These Years,


mudhouse said...

Hello Daywalker,
The 10x12 HF greenhouse comes with a steel base, so the aluminum frame isn't directly in contact with pressure treated lumber. But you're right, I just checked the current 6x8 HF greenhouse manual at the HF website, and it clearly shows the floor plates (which I assume are aluminum in your kit, as they were in mine) resting on the pressure treated 4x4s. I agree with you that this direct contact could lead to corrosion as the aluminum reacts with the chemicals in the treated lumber.

From my reading, a popular product used by builders to isolate aluminum from pressure treated wood is a peel-and-stick membrane, made of rubberized asphalt. It comes in a roll (rather like a big roll of thick duct tape) and should be available at the big box stores. The advantage of this is the sticky surface would keep it in place as you apply the top aluminum floor plate.

Even with the 10x12 kit, there was some concern about having the steel base in direct contact with pressure treated wood, and I recall reading that some folks simply used a layer of tar paper, cut to size, to separate the two materials. We used a blue foam sill insulation material that we had on hand (you can see it in the photos in Part Two, The Foundation) but it was rather annoying to keep in place, as it slid around while we attached the aluminum floor plates to the wood. I think a nice sticky membrane of rubberized asphalt would be a better solution than ours.

Also, something like the rubberized asphalt membrane tape might do a good job of closing the gap between the wood and the aluminum floor plate. If you're going to heat in the winter, you want to close those gaps as much as possible! Our (poor) choice of the foam sill insulation didn't help us in that regard, and I ended up caulking the seam inside and out with silicone caulk to give me a nice airtight seal there.

I hope this of luck with your greenhouse!

GEORGIA said...

Hi Mudhouse
Thank you, Thank you, THANK YOU!!!
We started building our greenhouse
in April - Still working on it and
I found your blog today while searching for an appropriate shade screen for my 10x12 sized house.
Would you have any suggestions on where to look for one that would fit? We will be starting the put in the panels soon and your blog just saved us a ton of work by letting us know about reinforcing it for strong winds. Again, thank you for putting your smarts out there and saving us from hours of frustration!

mudhouse said...

Hi Georgia, glad some of these ideas have helped. Many of them came from other Harbor Freight owners on the internet, and I am happy to share them, since we found them to be so helpful. (I do hope you'll consider the modifications for strength, and adding some screws to the panels, since we feel certain those steps have saved our greenhouse from serious problems in our windy climate.)

If you're asking about shade cloth, to use on the roof or walls, you may find you need to choose some type of shade cloth and do some simple fabricating to meet your needs. Some folks use it on the roof alone; others cover the roof and one or more walls. It depends on your climate and your needs, so we're all a bit different.

I bought Aluminet shade cloth from IGC
but there are many sources on the web. I found it to be very versatile. We made a cover for the roof by cutting it to size, and I made a simple hem by hand by folding it over and sewing with a big needle and nylon thread. Then we attached metal grommets on two edges (Harbor Freight grommet kit) and attached wooden trip to the roof edges, with screws to catch the grommets.

You can see pictures of the shiny silver Aluminet in this part of my blog, since I also used it to to make the removable screens for the south side of my greenhouse.

The hot afternoon sun streamed in mercilessly through the west gable end of our greenhouse (over the doors) so we built a lightweight wooden frame the same size as the gable, and then I stretched and stapled Aluminet to the frame. That now stays in place all year, here in sunny New Mexico.

I also made an Aluminet curtain (it's quite flexible) that hangs in the doorway to the greenhouse. It slides on shower curtain hooks. When my doors are open, the curtain is clipped to both sides of the opening, and that stops birds from flying in, but allows breezes and air flow. At night, I unclip the curtain, shove it aside, and close the doors. After four years of being yanked about, the curtain only has one small hole from all the wear and tear.

The greenhouse forum at GardenWeb probably has lots of threads from greenhouse owners showing how they have devised their own shade cloth solutions, and you might try browsing there too (using the search function at the bottom of the page.) Hope this helps! Best of luck to you with our new greenhouse,

mudhouse said...

I meant to provide a link to the GardenWeb greenhouse forum but goofed. Here's the link:
GardenWeb greenhouse forum

outdoor_artist said...

Dear Mudhouse,
What an amazing blog you have created! I just bought 2 of the HF 10x12 greenhouses to use for a completely different purpose. I want to build my girlfriend an outdoor art studio so she can work on her paintings and sculptures in natural light while being protected from wind and rain. I would like to connect the 2 greenhouses end to end to provide her 10x24 with the openings at both ends (it will be in a protected area from high wind). Have you come across anyone (or blog) who has done this with any possible tips? Also, is it easy to remove the doors to accommodate large sculptures in and out? Thank you in advance!!

mudhouse said...

Hello Gibson,
That sounds like an interesting use for the greenhouse! I can identify with the need for natural light; the bright but diffused light was one of the main benefits for my collection of succulents. Full sun in my climate here can be brutal for people and plants alike. It does get hot in there during the summer, even with my exhaust fan running full out. You could experiment with adding sections of screen, or even adding a portable evaporative cooler, if her workspace feels too warm.

I have seen several posts in forums about folks successfully joining these structures end-to-end, for one long greenhouse. This thread in the greenhouse forum of Gardenweb has links to a number of posts by others who've done this, with photos:
Connecting Two Harbor Freight Greenhouses

The doors are fairly easy to remove, but I find them rather fiddly to put back on. The wheels and guides need to fit into the tracks at the top and bottom, and we find it easier to put them back if we work person guiding the top, and the other guiding the bottom (I am usually the person with my ear in the dirt at the bottom track.) If you don't get the doors back in the track just right, they won't operate smoothly, so I tend to avoid removing them unless I have to. I have a small concern about the wear and tear on the door rollers if they had to be taken on and off very many times. The moving parts of this kit are, in my opinion, the weakest link. They do work, but they aren't exactly built like a tank. If they get out of alignment, they can be annoying. So once I get my doors happy, I tend not to mess with them very much, unless I just have to.

The opening with both doors fully open is 45" wide by 75" tall, so maybe you won't need to remove them very often. Removing one of the doors would gain you another 11" or so of width (both doors, another 22" or so.)

I'm sure you could brainstorm other door ideas as well. If you're crafty enough to deal with putting these structures end to end, I'll be you could also even replace the sliding doors with some kind of hinged doors, if that would be more convenient. These kits are only limited by the imagination and work that folks are willing to put into them.

I'd love to see photos of your project...consider doing a post someday at the Greenhouse Forum at GardenWeb! I'm sure others would enjoy seeing your girlfriend's greenhouse/studio. Best of luck! Sheri

Jamie Boyd said...

Hi Mudhouse,

THANK YOU! From the bottom of my heart (and my dear hubby's) for the excellent documentation and suggestions for this project. We just finished putting together our 10x12 HFGH, and I can hardly wait to get something inside it growing - it will, however, be a while since it is late October and we live in Southeast Ohio. I would like to mention,for those who are considering purchasing this kit, that there have been some improvements made since your kit was manufactured. Our kit had "extra parts" bags for many of the commonly used bolts, nuts, etc, and even had extra clips (which we used LIBERALLY.) It went up pretty smoothly, especially after we both spent the time to read your blog from beginning to end. I am designing the layout for shelving, benches, etc right now, and as I am sure you can agree it's so hard to decide exactly what you want. I just wanted to send you this note to thank you, and to let you know how much you sharing your experience has helped us. Happy planting!
J. Boyd

mudhouse said...

Hello Jamie, and thanks for the kind comments. It's good to know that Harbor Freight is now including some extra parts, including clips, and I really appreciate that update. Congratulations on your new greenhouse, I hope it brings you many years of happiness.

Sal G. said...

AMAZING work, SPECTACULAR documentation! I've picked up quite a few good tips already, and I haven't even read the entire blog. Will be bookmarking your blog for future reference as I build my very first greenhouse in Los Angeles, a HF 6x8. I'm sure your well-documented experience will come in handy during my construction and improvements.

P.S. You have a spelling error in one word in the section on building upper shelves. You spelled "selves." ;)

mudhouse said...

Hi Sal, good luck on your build. I think I found and fixed the typo, thanks!

Ladd said...

Hi Sheri...

Thank you so much for all you have done to help those who have followed after you! I have just purchased a HFGH 10 x 12 and am just waiting for the snow to go away (I'm in Layton, Utah). I was just wondering if you have any current comments on how your Greenhouse is holding up or if there is anything you would do differently in must be about six or seven years since you built yours. Also, could you post a picture of yourself (or someone else) in your greenhouse? Of all the pictures I've seen, I've never seen one with a real person in it (except the HF ad, and I'm not sure that is very realistic). Thanks again for all you've done! Ladd Christensen.

mudhouse said...

Hello Ladd, in August 2013 my greenhouse will have been standing for six years. It's holding up great except I've had to replace the roof panels due to deterioration from sun. This summer I'll also be replacing most of the wall panels, as they are also yellowed, cloudy, and riddled with small holes (patched with clear duct tape.) That's probably been the main disappointment with the kit. The Harbor Freight poly panels don't seem to have true UV protection, so they will deteriorate especially quickly in sunny hot climates. At least, my panels have. Folks in cooler climates don't seem to report as much of a problem, it seems to me.

My HFGH doors need some attention, as they're not sliding as smoothly as they once did. That's usually fixed when I vacuum the sand out of the track (followed up with a rinsing out with a hose) and lubricate the wheels. I suppose eventually I may have trouble with the wheels on the doors, after all these years, but so far they are still working. Fingers crossed.

No other problems at all. No wind damage, although it's frequently buffeted by bad winds here. The modifications first suggested by GardenWeb members have worked well for me (be sure to read that section of this blog when you build, and add those self-piercing screws and extra clips to the will need them!)

I understand your question about the photo, because the scale of the woman inside the HFGH 10x12 on the HF website does look goofy. She looks like a tiny midget in that photo (I suppose to make the greenhouse appear huge, so you'll run out and buy it.)

However, I don't have a pic of myself in the greenhouse. If you browse the GardenWeb greenhouse forum, and check out some of the recent Harbor Freight threads, I think you'll find some photos of folks standing in front of completed structures, and that might give you a better idea of scale. That forum is here: GardenWeb greenhouse forum

Good luck with your build!

Ladd said...


You said you cut the aluminum tape for taping the edges of the did you cut the tape? I haven't figured out a good way to cut it into smaller strips from the 2" rolls.



mudhouse said...

Ladd, I just cut a piece off the roll the same length as the end of the panel, and then cut it lengthwise in half with scissors, resulting in two (roughly) 1" wide pieces. I just eyeballed it, and didn't measure or mark to find the halfway point. It wasn't always perfectly even, but it's really not noticeable once the panels are installed.

Tricky thing is getting the 1" piece centered on the end of the panel before you fold both sides down. Very sticky stuff, once you pull off that paper backing! (Just remember it doesn't have to be perfect.) ;-)

Greg Treece said...

I had to chuckle at your comment about ensuring rain by starting a project best done in dry conditions. I live in Carson City, and it doesn't really rain here. I got the foundation work done on my HFGH yesterday, excited to get the walls up today. I woke up to rain! It rained steadily on me all day until about 3pm. It was not fun, but the frame is up.

The other thing I can now say with certainty, is that it slows your progress tremendously when you back over the base frame pieces with your truck when you're getting set up to work...

Thanks for the great info in your blog. I will say, the PDF of the manual I downloaded says "REV 12i" (not dated), and it's formatted differently than what came in the box (REV 10f). It did not give me any wrong directions that I can tell. A few of the pictures are still confusing, but they appear to have some additional clarifying statements added, based on your comments.

mudhouse said...

First of all, I'm seriously considering buying you a HFGH kit and flying you here to build the foundation in my yard, if that makes it rain all day. I'm pretty sure my drought-stressed neighbors will chip in.

Secondly, good for you for finding a way to make your greenhouse your own special creation, by adding unique tire textures to the base pieces. This process is all about making it your own. ;-)

Thanks for the update on the manual. My dog-eared manual says "revised 05/06" so it's high time for me to download the newest version and compare.

Good luck with the rest of your build (send rain.)

Kieth Larrimore said...

I have had my HFGH for about 5 years now in North Carolina. We have had several hail storms, several panels have blown off but have been found and replaced. I have reinforced the connection for the door with another channel of scrounged aluminum and braced the four corners diagonally to keep the whole thing from twisting in the wind. I have been thankful for the many comments, very useful, but I may have missed it. Is there any comment on where one can purchase replacement panels economically? Thanks again for hosing this blog.

mudhouse said...

Hello Kieth,
Hands down, the most economical source for replacement panels is Harbor Freight, but there's a reason they cost less. In sunny climates like mine they deteriorate after a number of years, requiring replacement again.

I replaced my roof panels in October 2011. At the time, the best price I found for good quality 4mm twinwall polycarbonate was from Farmtek. (I wanted to stay with 4mm because the slot at the roof ridge is only designed to accept a 4mm thickness.) When you price polycarbonate panels from greenhouse supply sites, be sure to inquire about the crating and shipping fees; that is usually what drives up the cost so high. If memory serves the Farmtek polycarbonate had a 10 year warranty.

I also considered Solexx, a translucent white greenhouse material that has excellent insulating qualities. Solexx ships in a roll, so you avoid the crating fees. I don't know if there would be issues with installation, as it is somewhat flexible, unlike the rigid poly panels we are used to. In the end, I was not sure I'd like the white color.

I ended up ordering Harbor Freight panels again (although I swore I wouldn't.) They shipped quickly and were already cut to the correct size; if you order polycarbonate from other places, you'll have to cut the pieces to size yourself.

It all boiled down to price, although I know I'll be replacing these again in a few years.

In October 2011, here were the prices for my three options, roof only, including shipping to my location:

Farmtek 4mm twinwall polycarbonate, about $410
Solexx 3.5 mm, about $350
Harbor Freight 4mm panels, $135

I cheaped out. You should probably do some research on the web to see if you can turn up a better deal on decent quality polycarbonate with real UV protection (especially if you have noticed any yellowing, cloudiness, brittleness, or holes in the HF panels in your location.)

However, if you cave (like me) and go the cheap route, Harbor Freight was able to ship quickly.

If others have been doing any similar research for pricing replacement panels, I hope they will post here.

Melody said...

Hello Sheri,
After putting up my HF greenhouse in Northern CA in 2009 via your instructions, I have just come back to your blog to see about replacement panels. Two of the roof panels sailed away into the neighbor's yard this winter, and another one bent back and broke.

All in all, it has been a wonderful greenhouse, and I have grown some great tomatoes in it, in our cool coastal weather.

A friend bought me a dwarf Meyer Lemon tree, which loves it in there!

So thanks for your wonderful instruction and pics, and good luck for a successful spring.

Sincerely, Merri

mudhouse said...

Hi Merri,
I'm sorry to hear that you're having to replace panels. I wish I had a less expensive source for panels that would last longer than the Harbor Freight panels.

Out of curiosity, do you think your roof panels were able to escape from any screws/extra clips, because they had started to deteriorate from the sun? I'm always curious to know if other regions have the same panel problems that we do, here in sunny southern NM.

I'm so glad the greenhouse has worked well for you, otherwise. My greenhouse also houses a number of wonderful plants gifted by very generous friends, and that makes them doubly special.

I'm looking forward to freeing many of my plants from the greenhouse soon, and getting them acclimated back to a sunny summer life on the patio. (I can almost hear them pounding little green fists on the greenhouse walls at night.)

Here's hoping your spring is successful, too.

Jyuma said...

I was truly impressed with the high level of effort that went into your superb instructions and comments.

Just followed your pictures was worth more than the written instructions in what laughingly passes for the official assembly instruction manual.

I'm up to the roof as of this writing and after seeing your pictures I can't wait to finish my 10 x 12 HF greenhouse.

Thanks for all your efforts.

mudhouse said...

Thank you Jyuma, and best of luck with your build!

Kublakahn2112 said...

I have finished my base and am going to use your blog every step of the way. Thank you so much for doing this. Its been a godsend.

mudhouse said...

I'm glad it has helped. Harbor Freight has updated their manual, and changed a few parts, since I wrote this blog. So, you may see a few discrepancies. If something stumps you, you are welcome to email me directly, too, at We'll be happy to try to help. I have a copy of the very latest manual, thanks to a kind greenhouse owner.

Steve Jackson said...

Hey mudhouse, what an awesome tutorial you have put together! I have, singlehandedly, assembled my GH and have most of the panels in place. Adding the reinforcements next. My only problem so far was the delay in starting the assembly after the 4X4 foundation was assembled. Turns out that while my lumber was true when purchased, as it sat in our local summer long, very unusual, monsoon it warped a bit and so my lil house is a bit tweaked. Thanks again for all the effort you put into the piece.

mudhouse said...

Good job Steve, hope you enjoy the greenhouse for many years to come. Sorry your long monsoon season warped your foundation lumber, but if you're a plant person, you probably thought the extra rain was worth the challenge of 4x4's with a little extra "character."

Good luck with your growing!

Dan Vera said...

I have built my 10 X 12 HFGH and used your blog and tips, getting ready to reinforce it since I live in the mountains of NY and have harsh winters. I plan to frame the inside with 4 x 4 posts on each corner and a 4X4 post at the back end, 4x4 posts framing the door and a 4x4 from the top of that to the roof. 2x4's completing the frame out and across the roof (doubled up) supported by the 4X4 post. From the outside screw the GH frame to the wood skeleton frame on the inside. This wood frame would allow me to build my benches off of. Also using a 20x24 utility poly sink. Thoughts/comments?

mudhouse said...

Hi Dan,
When people have posted about roof failures due to snow load, they indicate the Part 15 roof rafters themselves are the weak point. I think the most critical area to support is the center of each of the Part 15 roof rafters, so they can’t bow inward from the weight of the snow.

I posted a reply last year that included a number of links to threads on the GardenWeb greenhouse forum, and many of these threads show photos of how other HFGH owners have braced their structures for strength against snow load. You can go to section one, here...
Section One of this blog
...and then scroll through the comments at the bottom of the page, until you find my reply of April 8, 2012, to the poster named snwplwdrvr.

I always think attaching benches to the frame is a good idea too, as you indicated, to add more stability in general.

Another problem that some HFGH owners face in snowy climates is the sliding doors freezing shut, if the lower track fills with ice that freezes solid. This happened to me back in 2011 during a record breaking cold snap with snow. I think condensation ran down the inside of the doors, and froze in the interior side of the door track, where I could not access it for removal (although my two electric heaters kept the greenhouse warm, throughout the period.) For about two days I could not open the doors; I was afraid forcing them might do damage to the frame. If I had truly needed access, though, I could have simply unscrewed and unclipped one of the side wall panels, to enter that way, crawling under a bench. (This is one reason I’ve never liked the idea of caulking all the panels in place, as some folks do.) Thankfully I didn’t have to do that, but it did give me a taste of what some folks in icy climates were complaining about.

The above April 2012 post also has a few links to threads where folks have discussed replacing their sliding doors with hinged ones, if ice in the door track becomes too much of a problem for you. (I think many Harbor Freight owners are pretty innovative, and determined.)

I really like having a sink in my greenhouse, although some folks don’t like to sacrifice the space.

Hope this helps a bit!

Dan Vera said...

Sheri, thanks for the quick response I'm doing the reinforcement this weekend so your comment/idea will alter my plans to include a brace system for part 15. I'm thinking 4X4 post on each end of the GH centered 2 1/2-3' from the side and run a 2X4 standing on end across the parts 15 supported by the 4X4 post on the ends. Also I am going to put 3 EMT pipes side to side like you did the only difference is they will be mounted in flanges attached to the 2X4 frame on the side supported by 4x4 post on the corners. It may be a bit over engineered but it would be a diaster to lose the GH because of not enough support/reinforcement.
I plan on a three tier step shelf on one side, each step shelf 1 foot wide raising by 1 foot using wire shelving 12 feet long. On the opposite side a 20 x 24 utility sink with a 6 foot x 2 foot work bench, soil bin at the end of that run and a 2 or 3 tier step shelf at the back of the GH. If a 2 foot walkway will work I'll install a 1 foot by 6 foot center wire shelf 24-30" high. I have a drawing but don't know how to attach.

mudhouse said...

Hi Dan, sounds like you have a good plan. From reading other people's posts, supporting the center of those roof rafters is really the key point about dealing with snow weight, so that should be a big help.

I used 2' walkways in my greenhouse, using concrete pavers, and it works fine for me. Since I'm usually the only one in there, I don't need a lot of room. The only time I wish I had wider walkways is when I have some aggressively growing spiny plant that wants to reach out. Those get positioned pretty carefully!

I think we figured out a lot as we went along, stopping to compare notes we found on the internet from other HFGH owners. Sometimes it's easier to make final judgements about what you need for strength when you have the structure in front of you. With your good pre-planning I'll bet you end up with a very nice build.

Scotty said...

Do you think this greenhouse could be built on top of a small wall, maybe 2' foot high? I was thinking of adding a short wall as the base to dress the greenhouse up some. I would use block and/or some kind of stone or brick on the outside to dress it up. I would shorten the side walls up accordingly to keep the same overall height.

mudhouse said...

Hi Scotty,
I suppose this could be done, but we think it would add a lot of work. The polycarbonate panels could be easily shortened, and the vertical wall studs could be shortened (and re-drilled on the ends to accept mounting bolts) but the diagonal wall braces would also have to be modified. And you would have to figure out how to mount the steel base securely to the top of the masonry wall, of course, so it was pretty airtight.

Can't quite figure out how you would handle the doors. They slide open on the outside of the greenhouse, in a track, so you couldn't do any kind of stone or brickwork on the front part of the greenhouse, or the doors wouldn't have any place to go. I'm assuming your plan would be to leave the doors the full height, but I can't figure out how the front of the greenhouse could be modified to accommodate a rock or brick wall. (Maybe you already have a plan for this.)

One way around this problem would be to completely re-engineer the two doors so they were replaced by hinged storm doors. I've seen photos of folks who have done this, especially in snowy climates, since they don't like to deal with ice/snow build up in the door tracks. Of course, this is more work/problem solving, but it's possible.

There may be other considerations that I'm missing. Our first reaction was it might involve a lot more work, so it may boil down to how much time you want to put into it. I'm leaning towards thinking you might be better off to consider building a greenhouse from scratch, if a lower wall made of brick or stone is appealing to you (although I agree this is a wonderful look!)

As someone who stuffs her greenhouse full of plants during the winter, I will say that I'd hate to block the light from coming in the lower part of the walls. I have plants sitting on top of my benches in the winter, and another whole layer of many plants wintering under the benches, sitting on the ground. They benefit from the light coming in through the lowest part of the wall (it would be way too dark for them under the benches, if I had solid walls there.) But, you may not plan to be quite as crazed about stuffing every square inch full of plants, as I am. Just another point, in case it gives you food for thought.

I agree that these kits are often purchased by folks who are willing to put in the time and effort to re-engineer them to get the result they want. Almost anything is possible, with time and work, but any kind of re-engineering requires some extra time and problem solving (of course.)

If you do this, I hope you'll post a thread with photos to the greenhouse forum at Garden Web. I'd love to see your finished project!

Unknown said...

Scotty, I raised my greenhouse about one foot in order to create ground level vents to allow for a chimney effect during the summer to draw cooler ground level air in at the base as hot air flows out the roof vents. This really helps to cool the greenhouse, and the added roof height is also a plus in the summer heat. The one foot step over the doorway is not bad...
I used deck blocks and 2x8 boards, pretty simple and easy, and it actually stabilized the whole greenhouse quite well.

Cindy Clemmens said...

OMG this blog is amazing! I have been wanting a greenhouse forever it seems and finaly i'll be able to buy the 6X8 model. I had a friend in WV buy the hf one and she said it was horrible so of course i'm totally nervous as $260 is alot of money for me. Was so happy when I found your blog but wonder if any of your mods can be modified for the 6X8 model? This greenhouse is much shorter so not sure how to go about bracing. It's possible that I could build this in the corner of a 6ft chain link fence if that'd help but thinking that'd be more of a hindrance. I'm totally new to this and so afraid i'll do this wrong. Here in central IL we get horrible winds and tornados and this has been an especially brutal winter this year. lol I do plan to do the caulking at the base and for the panels. But like I said just not sure how to translate your other bracing mods to this smaller model and any help would be much appreciated. Thanks Cindy

mudhouse said...

Cindy, here is a link to an excellent blog about modifying a Harbor Freight 6x8. This owner chose to strengthen the structure by reinforcing with an interior framework of wood, that was part of his benches. Since you'll need some kind of benches anyway, I think this is a great idea.

Building and Improving the Harbor Freight 6x8 Greenhouse

He also accepts questions and comments on the site, so he might be a very good resource for you.

I think some kind of interior strengthening (and firm anchoring to the ground) is a better idea than securing to a chainlink fence, but mostly because I think it would be annoying to not be able to walk around the greenhouse. If you use shadecloth you'll be reaching all around the roof to secure it. Also, the panels go on the outside of the greenhouse, so I think you'd have to build the frame, attach the panels, and then move it into the fenced corner. That makes me a little nervous, since during that time (before it was well anchored to your foundation) the greenhouse is basically a giant box kite. You'd want to be very careful about any wind as you moved it.

Unfortunately people who buy the HF kit and don't know about the required modifications can have very unhappy experiences. Your friend may have just followed the manual, and may have lost panels as a result.

That's why I really don't recommend the kit to folks who aren't willing to put in some extra time and labor to strengthen it. But if you are willing to do so, or if you have someone who can help you with the critical parts, it can be a very good value.

I hope this helps!

Cindy Clemmens said...

Oh thank you thank you Sheri! So glad you've been through this and really appreciate your advice and love this blog and will check out the the blog too!

Pretty sure my friend just followed instructions.

Hopefully the instructions are way better than when you had to assemble yours?

I'm so excited to get this greenhouse! I live in central IL and the weather has been crazy this winter. I haven't seen this much snow and ice since I was a little kid. And i'ce never seen these extreme cold temps to the point that there's no school cause of the -10 to -40 degree wind chills. I pray I can make this greenhouse hold up to our weird winters and hot temps and tornado winds in the summer.

Sadly it's gonna be awhile till things around here thaw out :( So lots of time for planning!

Thank you thank you again!!!

mudhouse said...

You're welcome Cindy. HF has revised the 10x12 manual since we built ours, and it is a little better, so they've probably improved the 6x8 manual too.

One tip, if you buy your kit early, while waiting for better weather, be sure to go through the box and check each part against the parts list in the back of the manual.

It's not common, but it does happen that HF ships boxed kits that are missing parts. The sooner you discover this the better, so you can contact them. They used to be very slow to ship missing parts, and you don't want to discover you're missing a key part halfway through your build.

Stay warm! Spring will get here...someday...

Cindy Clemmens said...

Really hoping i'm not bugging you. But was watching some videos and came across this mod and wondered what you thought of it. That other blog was awesome but not sure i'd be able to afford or be able to make those mods and was wondering if your thought the mod in this video might work. Thanks again

mudhouse said...

Hi Cindy,
I think those mods will certainly help, but since we haven't built the 6x8, only the 10x12, we're really not comfortable predicting if that's all your structure will need. Some of these questions are hard because our climates differ, too, and it sounds like you need to plan for a lot of wind. (I'm sure you're aware...few greenhouses of any type would survive a tornado.)

Our guess is the 6x8 needs a bit less bracing than the 10x12, because it's shorter.

Even if the bracing requirements are a bit less for the smaller size, it's still critical for you to make sure the frame is well anchored to something in the ground that won't move (so the whole structure can't lift up in bad wind.) It needs to be very solidly anchored. Equally important is making sure the panels are securely attached to the frame, and we used screws for that, as shown in this blog.

When we built our 10x12, we made bracing decisions as we went, based on how strong the frame felt to us. If you haven't built anything like this before, I know that will be a difficult judgement for you to make. I think it would be a good idea to have someone help you with the build, just to have the security of another person's opinion, as you work.

It's always better to be extra cautious, and do more bracing than necessary, than to not do enough, and risk damage.

Cindy Clemmens said...

thank you thank you again. I will have 4-6 concrete anchors under 4 x 4's. We've had tornadoes get as close as 15 min away.

I totally missed screwing in the panels. Is that just the side panels?

I had planned on getting more clips and also using silicone.

Maybe even doubling up on those other flat braces that are already in the structure.

I'm just doing hardest to research as much as possible and try to find the best ideas that I can also afford to make this as sturdy and air tight as possible.

Thanks again!

mudhouse said...

Hi Cindy,
Part Six of this blog has information about how we added screws to our panels.
Adding the Panels

I know some folks use caulk to secure the panels; we have never tried that, and used screws instead. You may not need to do both, it's just that I don't have any experience using the caulk idea. Just be sure to do one or the other, for all of the panels on the greenhouse (and extra clips are very good, as you said.)

One reason we didn't use caulk is I wanted to be able to remove the panels of my greenhouse on occasion. In the summer time I take out some of the side panels and replace them with screens I made. It's easier for me to take panels off and put them back on later if I use screws instead of caulk.

The caulk is going to be pretty permanent, but that may not matter for you. Just different ways to go!

Albagrover said...

I just wanted to take a minute to also thank you for the blog. It was a huge help. I bought mine almost a year ago and when I read that step #1 was to excavate a hole 10'x12'x4" that is "perfectly level" I realized this was going to be a chore. I spent the 1st day figuring out how I could avoid step #1 and still shore up the flimsy base frame (I opted for treated 2x4s installed inside the base.) Seeing my frustration, my wife did some "surfing" and showed me your blog. It truly was a tremendous help and I have used many of your ideas (extra bracing of side walls, screws in panels, extra slide bolts to support shelves, etc.) Thank you so much for your time to post all of the info, advise, pix, and also for answering everyone's questions. I am certain you now have a "cult following." Thanks again.

mudhouse said...

Hi Albagrower, LOL, so far no signs of a cult following, but thank you for the nice words. (I suspect greenhouse owners and gardeners in general are way too sensible, stubborn and independent to make good cult members, but I might try some Alice Cooper eye make up...hmmm.)

I know the manuals and kits have changed slightly since I wrote this blog, so I'm glad to know there are still some helpful parts here. Best of luck with your greenhouse!

Old Buzzard 60 said...

Just finished HF 10X12 greenhouse. Have planted seeds and waiting!
Your help and pics were extremely helpful. Used many of your ideas with some modifications. It has been a couple of days in the wind & rain . So far no probs. Thanks so much for the tips, could not have done it without.

mudhouse said...

Old Buzzard 60, congratulations on your new greenhouse. I hope you enjoy it!

Dennis Ginn said...

Thanks mudhouse,
I was hesitant after buying the HFGH for my wife as a Christmas gift. I read your blog over and over to make construction go as smoothly as possible and so I would have a grasp on modifications needed to strengthen it. Our frame looks like yours except I had some left over 6" "C" purlin from our steel barn project that I cut into 24" lengths and pounded into the ground and then bolted the 6x6 treated beams to them. WE finished it on Sunday afternoon and it looked awesome. Fully reinforced but with only the originally recommended clips installed. I figured better to loose a panel in the spring and find out how they hold up. Anyway we ran to town to get pipe to plumb it and a small thunderstorm blew through. They said 15 to 20 mph winds. Well, it was destroyed. href="">photos
I have construction photos to add. Hope this helps folks out. greentreestables

mudhouse said...

Hello Dennis,
I'm very sorry this happened; it's beyond disheartening to see your work destroyed. I thank you for posting the link to your photos (I've included a clickable link below):

Greentreestables Harbor Freight greenhouse photos

My blog is the result of tips and advice from (mostly) Gardenweb greenhouse forum members, over the years, who learned from the failures and problems of previous Harbor Freight greenhouse owners. Posts like yours are difficult to read, but you're correct that they do serve to help others. We all learn from the foundation of experience built by other folks, and it was kind of you to post here.

As noted in the blog, the clips that Harbor Freight sends with the kit are not enough to safely secure the panels to the frame. We've had success following the advice of others for panel fastening, and that includes two elements: 1) ordering additional clips, to add more to each panel than Harbor Freight advises, and 2) screwing the panels to the aluminum frame, at least one or two screws per panel.

Our own experience with our 10x12 over the past seven years is the omission of either of the two steps will result in panel loss.

On one occasion, we missed the screw in one panel (after installing new roof panels two years ago.) Weeks later, in a very mild wind, that unscrewed panel did blow off the greenhouse, popping the clips as it went. It was the only panel we had missed screwing down, and it was the only panel that we've ever had come off the greenhouse. Most springs we have wind gusts in the 50mph range.

Additionally, I've had a few occasions when severe winds managed to unclip the edge of a panel, on the leading southwest corner of our greenhouse (it happens to get the worst of our wind.) On those occasions, the two central screws held the panel in place until I noticed the loose edge, and could apply more clips.

It's very easy to underestimate the damage caused by losing a panel. Under some mild conditions, all that happens is the panel comes out, and you can replace it; that's what happened with our roof panel. But more often, from my reading of years of posts on Gardenweb and elsewhere, it seems that the resulting sudden pressure changes inside the structure can cause the kind of total frame failure that you experienced. The aluminum alloy used by Harbor Freight is soft. If the wind forces rushing inside the structure are sudden and severe, when even a single panel fails, the frame can bend and collapse. I think it has to do with the violent and sudden pressure changes inside, and I think this can occur even when the wind and weather are not especially severe.

The key to avoiding this danger is to make sure no panels fail, and I truly apologize if my blog failed to make this danger more clear. Unfortunately, losing even one panel, if conditions are right, can lead to the loss of the whole structure.

I do thank you again for your posting your experience, and I hope you'll be able to enjoy the hobby of greenhousing in your future.

Dennis Ginn said...

It will come back to life. I'm building the new frame out of 2x4 lumber. I'll install the panels with wooden battens and i hope tosalvage the roof structure that came off. We'll see.

Fran Lebowitz said...

Did you install the electrical components and wiring yourself, or use an electrician?

mudhouse said...

Dennis, good for you, and I hope the new construction goes well for you. Again, sorry you had the heartbreak of losing your first structure.

Fran, our city building code requires the wiring to be done by a licensed electrician, but I think this can vary, depending on local codes and your own location (in our previous home in another state, and in a more rural setting, there were fewer requirements.) You might check with your city codes department.

Bob Kelshaw said...

Hello from North Georgia!

Just wanted to post a note of thanks to you for this blog, I carefully followed your suggestions for the most part, (still need to order more clips) our foundation took the most time since we placed it on a hill in the back yard. just finished a 6X10 deck in the front as an entrance. The time you spent on this blog was invaluable to us in putting this up. THANK YOU!

mudhouse said...

Howdy Bob,
Thanks for your post. I know the manual and kit has changed a bit over the years, so it's nice to know that some of the info here is still helpful.

That deck in front sounds great. Much of our yard is sloping, too, and that does create a challenge. But I always think slopes and hills can be quite beautiful (and more interesting) when they're well utilized. Good luck with your greenhouse!

Darren Donovan said...

Hi Sheri,
How high above the ground are your 3 GFCI outlets? Are they near one another, or spread out at different parts of the GH? Since my GH use is only in the cold months, do you think I'll need a fan? I'm hoping that by using the Bayliss auto vents, that'll be enough air circulation. Where do you position the heater? So many questions, I know. Thanks a lot for all your help, I got the frame up, doing the roof next.

mudhouse said...

Hello Darren, I suspect everyone does these things differently.

I had the outlets installed above my bench tops, for convenience. Each one is on a different wall. You may also want to consider how and where you will water your plants, when considering location of electrical outlets. Also, electric heaters pull a lot of current, so the input of a good electrician is important. (Your local codes may require that, too.)

My two heaters sit on the concrete paver floor, about six feet apart, but I think others may locate them differently.

There are two basic reasons for fans in a greenhouse. One is to exchange the air (exhaust fan) and the other is to keep the air moving (circulation fans.) I use one exhaust fan that runs when temps go above 90F inside the greenhouse, and two cheapo oscillating fans that run 24-7, all year long, to always keep the air moving inside the greenhouse. One cheapo fan sits on a shelf close to the back wall, and the other is mounted on the wall over the doors. This is just the arrangement I've ended up with; I'll bet everyone has their own set up, after trial and error, and depending on how they use their greenhouse.

Good air circulation helps plants grow better and reduces the chances of plant disease problems, so I always want the air in there to be moving, even when the greenhouse is closed due to cold weather.

I would recommend looking for The Greenhouse Gardener's Companion by Shane Smith. It's been beloved for years by greenhouse owners, and it covers a lot of very helpful basic information. You can buy it on Amazon.

Darren Donovan said...

Thanks so much mudhouse for your answer. After more thoughts, I think I'm gonna get a 3-speed 16" fan (like yours), 2 motorized shutters, 3 plug-in thermostats (1 for the fan, 1 for the 2 heaters, 1 for the 2 shutters), and 2 electric heaters. What heaters do you have? I used littlegreenhouse's BTU calculator, and found that to maintain 60F inside, with the outside average temp of 40F, I'd need about 11000 BTU. I checked Amazon, and found a Lasko 5307 oscillating ceramic electric heater (1500 W, 5100 BTU), so I think I'll get 2. Do you see anything in my plan that can be improved?
Have a great day!

mudhouse said...

Hello Darren, my heaters are just inexpensive Honeywell 1500w heaters (Walmart I believe.)

Because I pack my greenhouse floor so tightly with plants in the winter (it's pretty ridiculous) I don't think I could use an oscillating heater, since I avoid having the hot air blow directly on my plants. I move the heaters out of place when I'm watering, because water and electricity don't mix. I put them back in position later. Once I forgot, and left a heater blowing right on a Gasteria overnight, and it fried the poor plant on one side.

I have the heaters pointed towards my open walkways between the benches, so they are just facing open air. Again, this is just my take, and might not fit your needs. We all structure our greenhouses differently inside.

If you're thinking of using the same thermostats I show in this blog, you will need one for each heater. An electrician can help you sort out your needs in this area. Hope this helps!

Charles Garrett said...

Thank you for the great step by step and photos. I had the misfortune of attempting to use one of those "tent" type greenhouses. It folded in the first rain. So did it's replacement. I've been looking at the HFGH and stumbled across your blog while researching. GREAT STUFF! You've done a great service for this novice grower.

mudhouse said...

Thanks Charles. I know there is a lot to wade through here, but if you do you'll see the Harbor Freight greenhouses have some strengths and some weaknesses. However, if folks are willing to do a little brainstorming and extra work, I still maintain they can be an excellent value, especially for those who want to try having a greenhouse, without investing thousands.

They are not for everyone, but for some of us, they are still a good fit. Best of luck to you,

Charles Kiplinger said...


How has adding the 40% Aluminet been for higher winds? Seems the additional airflow in the side of the greenhouse could cause panels to pop out. Really like the additional work you have done to the HFGH. Am considering putting two together.


mudhouse said...

Kip, I wasn't sure about that myself, when first installing the removable Aluminet screens on the south side. It hasn't been a problem at all, however. I think it's probably because our strongest winds hardly ever come from the south; most of the time they hammer the doors on my west end. (I keep the doors clamped shut with two clamps on bad wind days.)

So, I can have very bad winds blowing directly on the doors on the west end, but even with the doors shut, I don't seem to have any problem with wind rushing inside through the screens on the south side.

Maybe it's partly because I have such a large area screened...four of the six side panels...a larger area for the air to move in and out without much restriction? I'm not sure.

A bit of wind/air can also escape through the floppy horizontal louvers of my exhaust fan, on the east end, opposite the doors. Sometimes I notice those little flaps banging open for a second, then falling closed again. I suppose that lets small errant gusts escape too.

I'm guessing others might have a different experience, based on their GH orientation, and the direction of the prevailing breezes. But I love those screens, they've worked out very well for me, in this location.

Keith Lake said...

Wanted to get your opinion on something I'm wanting to do with this greenhouse. Instead of building it as a stand alone structure, I was wanting to have a lean-to greenhouse on the south side of my house. I was thinking about putting each half fastened to the house, so the ridge, would be fastened to the house.In other words I would be splitting the green house length way,and putting them end to end, making it 24" long. Thoughts, ideas????


mudhouse said...

Hello Oscarsmartdog,
If there is one thing I've learned, it's that anything is possible. This kit seems to appeal to folks who are willing to do some re-engineering to use it in different ways.

I've seen photos of folks joining two 8x10 HFGHs, end to end, for a 24' long single structure. That seems to work fine. I think splitting it in half will be a lot more difficult. You'll have to reinvent the bracing that is designed to go corner-to-corner on both ends. I think you'd also have to discard the top rail at the roof peak (because you only get one of those, and I doubt you can saw it in half) and build something to accept the poly panels at the peak, where it attaches to your house.

The sliding doors will also have to be re-engineered, or probably discarded entirely, in favor of building your own hinged door (some folks prefer this anyway, and if you search enough on the web, you can probably find accounts with photos.)

I worry that splitting it in half lengthwise would cause a large amount of work, because the design of the aluminum frame doesn't make it easy for you. When I add in the poor quality of Harbor Freight polycarbonate panels (almost no UV protection, in my opinion) I'd honestly suggest you also investigate building the structure you need, perhaps out of wood, and glazing it with a better quality twinwall polycarbonate product from a greenhouse supply company. I don't think it would be a lot more work than trying to retrofit the HFGH the way you describe. It would cost a bit more, because the polycarbonate panels (real ones, not HF panels) are not inexpensive, but you might have a much better structure that would last longer, and it might look like a higher quality permanent addition to your house (if that's a concern.)

Also, you could then build it the width you'd want. I would find a 5' wide lean-to greenhouse a bit too tight, I think, but this is a matter of personal preference!

I hope this doesn't sound too negative; I've seen folks do some very creative things with these kits. This is just a heads up that altering the framing to make this work seems pretty difficult, to me. You might go to the HF website, and download a manual for the 10x12. You can really study the drawings of the framework, to think about what you'd be cutting in half or losing, and it might help you troubleshoot some of the issues above.

Brainstorming and thinking outside of the box often lead to very good things, and I hope you have good luck with your venture!

Michael Soudant said...

I plan to begin this scary project this spring. I am in North Central Nebraska with all known weather extremes. I am so happy that this site is still here and hope you keep it available as without it I don't think I would try this project. So called instructions are a horror. Soon I will order extras on clips, bolts, washers etc. before beginning. Thanks for all of your efforts.

Michael Soudant

mudhouse said...

Hi Michael, I hope it's not really a scary project! Just go slow and enjoy the process (we just took our own sweet time.) And just a note, while you're waiting to start, this is a good time to compare your kit parts to the parts list in the back of the manual...just to be sure everything is there. It's not common but occasionally folks do wind up missing a part, and depending where you are in the build, I guess that could be scary (and surely annoying.)

SilverDollarSaloon said...

I have this same Greenhouse with one big problem.

What do you do for replacement panels when they all go rotten after a few years from sun damage.They turn brittle and crack all apart.

mudhouse said...

Hi SilverDollarSaloon,
Yes, this has been a very disappointing shortcoming of the kit. Some people seem to get longer use than others, but clearly the Harbor Freight polycarbonate panels do not have the UV protection present in the polycarbonate sold by other companies.

We've replaced our roof once already, with more Harbor Freight panels, and I'm getting ready to replace it again soon (along with most of the wall panels, this time.) You can buy more panels individually from Harbor Freight, but you'll have the same problem eventually, so you're really just kicking the can down the road. Some greenhouse supply companies sell 4mm twinwall polycarbonate that you can cut to the same size and shape as the HF panels. However, it's not inexpensive. The upside is, most of this material from other companies has a 10 year warranty.

You could buy thicker twinwall polycarbonate to use from greenhouse supply companies, but be aware that the roof ridge will only accept 4mm thickness, so you'd have to figure out a way to deal with that problem, if you use anything over 4mm.

There are some recent posts on the topic at the end of my section on Adding the Panels. Click here, and scroll down to the newest comments, for some thoughts about what others are considering.
Adding the Panels

mudhouse said...

One more thing, SilverDollarSaloon. If you do decide to buy yourself another few years by ordering replacement panels from Harbor Freight, be aware that there are two versions of the 10x12 greenhouse.

You can find the model number by looking at the front page of your manual. (It will either be 69893, or 93358.) The HF website only shows one version currently, but you'll need to be sure you specify WHICH version you have, when you call up to order panels. There are some differences in the panel sizes on the back wall, if I'm remembering correctly.

Hope this helps a bit. I know it' a huge aggravation and disappointment!

MarcusMcCormick said...

How did you put the extra UV 6ml film on the plastic panels? HELP PLEASE ( :

mudhouse said...

Hi Marcus,
I have never added UV film to any of my panels. I do currently have a big sheet of UV greenhouse plastic stretched over my entire greenhouse roof, because we had a hail storm in October, and I needed a quick way to waterproof the whole roof for the winter.

Here's a link to the blog of a Harbor Freight greenhouse owner who did apply 6ml UV greenhouse film to each of his polycarbonate panels. It's written for a 6x8 Harbor Freight greenhouse. If you go to Step 6 of his blog, he does a wonderful job of explaining how he secured the film to his polycarbonate panels, using HVAC foil tape. I hope this helps!
Building and Improving the Harbor Freight 6x8 Greenhouse

MarcusMcCormick said...


Wulf Man said...

Hello Been building my 10x12 greenhouse this week. We did a few things different than you did. We poured a 4" perimeter stem wall for the greenhouse. We attached the steel base to the stem wall with angle iron bolted to the concrete with redheads and 1/4-20 bolts with nylock nuts. We decided that just bolts and nuts were a poor choice so we added some lock washers to every connection. Every opening where a panel goes we pop riveted it to the steel base. We have decided to apply lots of extra clips to the panels per your advice as we get very high winds in the spring. I am leaning toward installing 1/4" cables over each end of the greenhouse and securing them to the concrete foundation. We decided to spray all panels before installation with marine urethane spar varnish for UV protection. Only time will tell if that's a good choice. We can reapply more next year if we see a change in the panels. We have taken pictures and can send them to you if your interested in other perspectives on assembly.
Thanks for all your information on assembly.

mudhouse said...

Hi Wulf Man,
Thank you for posting good details about your build; I'm sure it will help those reading here in the future. At this time, I'm not adding photos to the blog. However, you could consider starting a thread in the GardenWeb greenhouse forum, and include your photos there. That way other internet readers could see the fruits of your labor!
GardenWeb Greenhouse Forum

Sounds like you are well on your way to a good sound structure. I hope you enjoy it for many years to come, and I'm glad the blog was of some help to you.

MarcusMcCormick said...

Hi Wulf Man,

I have been following some of mudhouse's posts because they are so great! Thank you mudhouse.

So, I got this last posting and thought I'd share what I found out about protecting the panels from UV on the greenhouse. I think I read it somewhere on GardenWb Greenhouse Forum.

mudhouse and other folks recommended Top Secret and some of them had painted it on the panels as long as 3 years (?) ago and the panel still look great. It is a two step (epoxy) process and you really don't want to get it on your skin or breathe it.

I sure hope I used the right product..the website is VERY confusing. I went with the one called TS-100 Silicone Epoxy. I was listed under flooring, but one of the Webgarden folks mentioned it by name.


mudhouse said...

Hi Marcus!
The link you posted above, to the TS-100, is the same product I ordered from that site. It is a confusing website (and I found the ordering process to be a little glitchy too, but it was years ago.) They have the TS-100 listed under different several categories on the site.

The TS-100 product is actually not a true epoxy (in my opinion) because it does not involve two parts or two steps. It's a single product you roll or brush on, after thinning with their proprietary thinner. (So, I find the name a little confusing, too.) I found it very easy to apply with a fine nap roller. I did two coats; other folks I read about did three coats.

My updated evaluation about the product is that it did seem to help. I think it delayed the deterioration on my roof panels (the only panels I treated.) But in my harsh sunny climate, they still failed; they were getting brittle, and yellow, with tiny holes forming in the outside layer. An October hail storm was the last insult they could handle. These new panels, treated with the TS-100, had been in place about three and a half years, under Aluminet shadecloth year round.

So I really don't know what the best solution is, at this point, to protect new Harbor Freight panels. I think some folks in milder climates may have better luck with a variety of protective measures; maybe Wulf Man can keep us posted about how his panels fare. I do wish Harbor Freight could improve the quality of their panel material, but I'm sure that would increase the price of the kit I doubt changes are upcoming. Too bad, because this is probably the biggest shortcoming of the kit.

Meso said...

Hi mudhouse,

Excuse the change of User Name. (at least I hope it now shows Meso) Hubby made a mistake and used his real name...duh. I follow and have chatted with you, mudhouse, on gardenweb, but different user name there. oops.

mudhouse, THANK YOU for the update. I agree with your description of the TS-100 and it's website. I have NOT been able to put up my greenhouse yet....only been trying to for over two years...wouldn't want to rush into anything. ( : Reasons for delay are mentioned on gardenweb.

I probably won't have a chance of starting on it until October or November, if I even get to work on it this year. Everything is on hold. Seriously, I am still on my Jan. to do list!

The blessing in that is that it has given me time to learn more. I'm attempting the SHCS on it. So, if you or Wulf Man find out anything better I can try it. I don't think it would hurt to put something over the panels.

Michael Soudant said...

I spoke to the folks at Harbor Freight recently about my 10 x 12 greenhouse. I whined about how poor the illustrations are in the manual and they emailed me about 30 photographs which do a better job showing what we need to see for assembly.Make sure that you have the "item number."

mudhouse said...

Ah, gotcha, Meso! Yeah, I wish we could all find a good, long term solution for the short-term lasting ability of the Harbor Freight panels. Sadly I have just accepted the fact that the (low? or non-existant?) UV protection on these HF panels is part of the reason the kit is so reasonably priced. Polycarbonate panels, with true UV protection, and a ten year warranty, are really expensive. I know because I'm probably getting ready to buy some, and redo our HF greenhouse. I'm getting too old to enjoy replacing the roof panels (again.)

This panel problem adds weight to the argument against the Harbor Freight greenhouse. I still maintain that the kit, with all the weaknesses, has been a fit for us. After almost 9 years, the sliding doors are a little fussy in the tracks, and the panels are (as discussed) an ongoing problem. But, the frame is solid, and it continues to house a huge number of plants for me, 24/7. I just wasn't ready, when we bought this kit, to plunge many thousands into a hobby I knew nothing about. The Harbor Freight kit gave me the entry I needed, so I am grateful.

And, for what it's worth, the panels on the north side of my greenhouse, protected from the sun by insulation on the inside, and by the shelter of our house on the outside, look like new, after nine years. It's simply exposure to the sun, so how much you get affects how unhappy you will be with the panels.

If I was putting up a new HF kit I'd probably still coat the panels with the TS-100 product, two or three coats, because I do think it helps...somewhat. And/or, I'd attack the internet with more research for something similar, because it's been a number of years since I turned up the TS-100 product by the Top Secret company. But I'd also bet that eventually, in a sunny climate, I'd probably be replacing them with something better. Real polycarbonate...or maybe Solexx. (Steely-eyed realist, here.) Who knows, maybe one of our intrepid HF community will pop up with a better solution.

I hope things continue to get better for you. We "aged" our kit in the box for a long time too, and it doesn't hurt a thing, as long as you don't leave the plastic-covered panels exposed to the sun or a lot of heat. (The protective plastic can fuse to the panels, if exposed to sun/heat.)

To be honest I always encourage folks to try to tackle this project slowly and have fun with it. Most gardeners are certainly "process" people anyway. (I can't think of a hobby that encourages more patience, can you?) The only folks I really worry about are those who contact me and ask, "can I get this up and running in an afternoon?"

Yep, that worries me. :-)

Best of luck to you!

mudhouse said...

Hi Michael,
Thanks for letting us know, I did not know they would email photos to help assist with the assembly. You're also absolutely right about needing the Item Number for the greenhouse (I tell folks to look on the front of the manual.)

There are two different versions of the 10x12 Harbor Freight greenhouse in the market currently...with slight differences in some of the parts...although the website is now listing only one model.

Thanks for the update on how to get more help!