Part Four: Assembling the Roof, Windows, and Doors

There are two ways to build the roof frame. The manual tells you to assemble the roof frame on the ground, and then (using assistance) lift it up and place it on top of your walls. I’ve read this actually isn’t as difficult as it sounds. However, there were only two of us building this, so we decided to assemble the roof on top of the walls, piece by piece. It’s actually quite easy also.

First, we attached Parts 8 and 9 on each end of the greenhouse, to form the gables.

Second, we attached Parts 10 and 11 on the ground to make the Crown.

Third, using two ladders, we fastened the Crown to the top.

At this point it’s easy to lay the Roof Studs (part 15) on top of the roof in place. Using a tall ladder inside the greenhouse, we attached the top of each roof stud to the holes in the Crown. That leaves the ends of the roof studs resting loosely on the wall tops, so you can (oh goody!) slide more bolts in the tracks.

In the photo above, the roof ends (parts 8, 9) are in place, the roof crown is up, and we’re starting to lay out the roof studs on top.

Good news, the manual is correct on page 13 when it tells you how to install the bolts in the roof studs. But, those counts are only correct if you plan on installing the roof vent windows in the positions shown in the manual. We decided to put all four of our vents on one side of the greenhouse, so I had to refigure which bolts to stack in each stud.

It’s really not hard. Figure out where you want your roof vents, and look at the illustration on page 13. To start with, each roof stud is attached with a short bolt at the top. Then, if the roof stud is crossed by one Horizontal brace, you need one long bolt floating. If the roof stud is crossed by two Horizontal braces, you need two long bolts floating. If the roof stud attaches to either side of a window vent, you need a short bolt floating, ABOVE the long bolts used to secure the braces. And finally, you’ll need a short bolt at the bottom of the stud, to attach it to the top of the wall frame. If you just study the drawing and think about what each stud needs, you can figure it out.

As with the Part 30 braces for the walls, be sure you’re pointing the arrow stickers on the roof braces into the corners. The photo above shows the roof frame complete.

A Note About Part 42, Window Support Beams

Page 13, step 5 has you sliding the window support beam (part 42) onto the roof studs where you want to position your window. This piece will eventually snug up against the bottom of the window. I managed to put these on upside down the first time; the correct orientation is shown in the photo to the right, with the U-shaped openings for the bolts pointing down towards the ground, and the flat part (with the part 42 stickers) facing inside the greenhouse.

Also, see those two tiny drilled holes in Part 42? Those are to attach Part 50, which is the little tab that will catch in the holes of your window handles when you prop the vents open. For some reason, the manual doesn't have you attach Part 50 to Part 42 until after you've installed the windows. At that point, you're up on a ladder, squinting in the sun, and trying to screw very tiny screws in place, one of which will most certainly fall in the dirt. And no, they don't include extras.

Tip: You might as well attach those little Part 50 tabs to Part 42 right now, while you're standing on Good Mother Earth. Then they will look like the picture above, and you can go ahead and install them in the roof frame.

Assembling the Roof Vent Windows

For each window frame, you attach two side pieces to the top piece, slide in the polycarbonate window, and attach the bottom piece of the frame. It wasn't clear to me how to orient the handle from the instructions, so here’s a photo of the bottom edge of an assembled window. This side of the window will face inside the greenhouse (the handle will hang down inside the greenhouse so you can open and close the window.)

I'm not impressed with the quality of the handles. One handle had a rough edge that prevented it from moving easily, but the aluminum is very soft, and it just took a second to smooth it out with a small file.

The Loose Window Panel Problem:

This problem apparently only occurs in some kits. It did occur in my kit. When I assembled the windows, I noticed the polycarbonate window panels fit tightly in the frame from side to side, but they could move up and down in the frame by nearly 1/2".

I decided not to worry about it, and installed the windows anyway. Several months later, this caused a problem. During a very strong wind, one of the window poly panels actually blew part way out of the window frame (the poly panel slid up enough to expose the bottom edge, and the wind caught it.)

We ended up taking down all four windows and caulking each poly panel in place with clear caulk, on the outside of the window. If I build another Harbor Freight greenhouse, I'll check to see if the window panels fit snugly in the window frame. If they don't, I'll caulk them in place from the start, before I ever install the windows in the roof. (Be sure your frames are nice and square before you apply any caulk.) Since I caulked the poly panels in, I've had no more problems with the panels moving in the window frames.

One more note...if you ever do have to take down the windows, after your greenhouse is all assembled, as we did, please take note of the order you remove them, and put them back in the same order. We didn't do this, assuming the fit was the same for each window opening. Apparently it's not, and once the roof panels are in place, it's very hard to make any adjustments to the window openings. My windows have not fit as well since we took them down (and put them back in a different order.) Rats!

Installing the Windows in the Roof

Amazingly, I found the directions for installing the windows confusing!

The highest part of the roof (the roof crown) is made of parts 10 and 11. The very top of the roof crown forms a groove or track that runs the entire length of the roof on both sides (where the red arrow is pointing in the photo to the right.)

To install the windows, take them one a time to the peak of the roof, at the end where the track starts, and slide the top of the window into the track on the side of the roof where you want your windows. (You can put your windows on both sides of the roof, or all on one side.) Holding the bottom of the window, you can now slide it to wherever you want it in the roof. Then lay it down in position, and it will hang in place.

You can also look at the bottom drawing on page 14, which shows a cross section view of the window frame top (part 38) sliding into the track in the roof crown (parts 10/11.)

When the windows are where you want them, you snug part 42 up to the bottom of your window.

If you’re ganging windows together, as I did, the Parts 42 just overlap each other, and share the same bolt in the track, as you can see in the far right of this photo.

I ganged all four windows together on one side, and I had to do a bit of adjusting and wiggling to get all the windows to open smoothly.

All four windows are now installed.

Tip: In this photo, see how all four of the window vent handles are just hanging straight down? Don't do that. Here's why.

Instead of locking the handles into the (part 50) peg on the window frame, I left those handles hanging down while we were installing panels. Suddenly (did I mention it's windy here?) an odd wind came up under one vent window, popped it wide open, and then bent it backwards until it popped out of the track and flew about 8 feet. Landed on the roof of our house. Very exciting.

Nothing was broken, and we just slid it back into the track. This would not have happened if I had fastened the window handles onto the peg on the frame, into any one of the holes. In the right wind, the vents can still open up a bit, even in the tightest (lock down) position on the handle. But, it sure won't flip over backwards and land on your roof. Keep 'em secured!

Assembling the Sliding Doors

The door has also been redesigned along the way. The newer version (mine) has tracks to hold the poly panels in place, and the old version had small pegs to hold the panels in place.

Frankly, I could not make heads or tails out of the drawings or instructions on page 15 for assembling the doors. I think it may be the worst page in the manual, and I wonder if the instructions have gotten a bit muddled during the design change. The two lower illustrations are important, but for the general fitting-together-of-pieces I found photos online to be much more helpful, so I've included a lot of pics here.

A picnic table is a good work height for assembling the doors.

Here’s a completed door, front side up. The top and bottom of the door has wheels that slide on the tracks in the door frame. The black rubber gasket will face the greenhouse. If your rubber gaskets are sticking out beyond the frame end, just wiggle them in the track until they’re flush.

Note: Each poly panel in the door slides into a fairly tight groove in the cross braces. If you’re sealing the edges of your panels with aluminum tape (see the section on Adding the Panels) you should just skip taping these panels; the edges won’t be open to the elements anyway, and it can make it really hard to get the panels in (especially if the poly panel has any kind of a burr on the cut edge.) I taped all eight door poly panels before I understood how the door was assembled, and it caused me grief!

If you find that some of your door poly panels will not slide into the grooves in the door parts, they may have a cutting burr on the edge of the poly panel, making the edge just a bit too fat to slip into the groove. I found I could take a pair of wide-jaw pliers, and working along the panel edge, just squeeze the edge gently to compress it a bit. Not much...a snug fit is better to decrease air leaks, but you can do this if the poly panels seem too fat to go into the grooves.

All of the horizontal parts are attached by putting screws through the slotted holes in the side pieces (part 33). Be sure the arrow stickers on the central braces (part 36) point up as you install them.

I attached all the horizontal pieces (top, bottom, central braces) to one side piece (part 33) first, fitting the polycarbonate panels (part 64) in place as I worked down the door. Then I attached the other side piece (part 33.) Generally the whole process takes a bit of fiddling and sliding parts around to hold all four of the poly panels tight. I believe you could assemble the parts with the rubber gasket up (viewing the back of the door) or with the rubber gasket down (viewing the front)...whatever works for you.


There are two small black plastic pieces (part 51) that get inserted in each end of the bottom rail (part 37) before you attach it.

Because the holes for the screws are slotted, you can adjust this part to either be high or low. When we installed the doors, we found the small black pieces (part 51) had to be adjusted as low as possible so they would fit over the floor plate.

Tip: After we installed the doors, I also found that some fiddling/adjusting of this part controlled how easily the door would slide over the bottom rail. You might need to play with it.




Here’s the bottom door corner, shown from the back of the door:













Here’s a front top door corner. You bolt the top door frame (part 35) to the Door Slider (part 34, which has the wheels that slide on the track.) This is how it looks from the front.









Here's how a top corner looks from the back.
This is one of the wheels that slides on the track at the top of the door, and the black rubber gasket will be touching the front of the greenhouse.






Installing the Sliding Doors

One of us slid the top wheel on the track at the top, and the other guided the bottom onto the bottom track. This is fiddly because of the small black plastic clip that has to be threaded onto the bottom track, and I pretty much had my ear in the dirt to see that it was lined up correctly.


VERY Important Tip: There's a very important small illustration at the bottom of page 15, labelled Side View. It's shown to the right. This shows you that the small black plastic clip Part 51 has to be guided onto the bottom door track so the small vertical part of the aluminum track is actually threaded up into the vertical gap in the center of black plastic part 51. If you do it right, the bottom leg of the black plastic "L shape" goes down the front and under the L-shaped aluminum door track, as the illustration shows.

Note: It's actually possible to install the doors incorrectly at the bottom, so that the black plastic part 51 is just sitting on top of the door track, sliding along in the small valley there. This is not right. Although your doors can function (sort of) this way, they can also fall off, since they're not truly captured at the bottom in the manner the kit intends. This also means your doors could more easily blow out in a big wind, so be sure you've installed that bottom part correctly. When they're installed right, the doors are firmly captured at the top and the bottom.

There’s one joint in the floor plate that was difficult to get the left door over. Once you get it over the joint, you’re home free, but it was hard. We had to adjust that black plastic part 51 down as far down as we could, using the screw closest to it, and even then it took a lot of gentle tugging and bad words.

Fine-Tuning the Doors

You'll want to come back and deal with this part much later, when the rest of your greenhouse is completed, but I'll include it here since we're talking about doors in this section.

When I was done with the doors, and had adjusted every screw I could find of to get them sliding freely, I was very happy with how easily they moved. But I still had a gap between the two doors; a good quarter inch at the bottom, and slightly less at the top. Some people have reported that their doors have a uniform gap between them; others (like me) have a gap slightly larger at the bottom. Either way, it's annoying, and no good for holding in the heat during the winter. See photo to right.

I first tried to fix this gap by buying some high quality 1/4" rubber door gasket, and attaching it with screws to both doors. This didn't work; the doors slide so freely that they just moved the same distance apart, and so I had the same gap, but nicely lined with $7 worth of pretty white door gasket. Crud.

Even worse, if you use more weather stripping than you need to close the space between the two doors, you also create NEW gaps at the far edges of the doors, because you're now moving the black rubber door gasket further away from the metal greenhouse frame than the kit intended. To see what I mean, just open up your doors so there's a very small gap between them, and then feel the outer edge of the door, where the black gasket is. You'll feel the gap where warm air could escape.

So, first lesson is, I found that plain foam weather stripping (the closed cell type, so it won't soak up rain water) worked better on my door gap than rigid rubber door gasket. I needed something that would close down the gap, but would compress easily under pressure. You may need to experiment to determine what works best for your own door gap situation.


After I'd changed out the weatherstripping in the gap between the doors, I found I still needed to apply a strip of foam weatherstripping to the outer edges of the doors, under the black rubber door gasket, to really close down any potential air leaks around the doors.

This photo shows how I just held the black rubber door gasket out of the way, so I could affix the self-adhesive foam weatherstripping to the frame right under the gasket. This allows the rubber gasket to hit against the foam stripping, and to make good contact the whole length of the door. Now I have a good tight seal around the outer edges of my doors when they are closed, and a good seal in the center between the two doors.

Now, on to the question of keeping the doors closed. Since my doors slide so easily, they can actually be opened by a strong wind blowing directly on them. Someday we may figure out a way to build a special latch, but in the meanwhile I'm happy with my unlovely but functional clamp. The clamp has a lot of strength (takes both hands for me to open it) so I don't worry about it popping off, and it thoroughly compresses my weather stripping between the two doors. Recently we had about nine hours of winds in the 30-40mph range, blowing directly on my greenhouse doors. Since they were actually predicting gusts over 60mph, I added an additional two clamps (top and bottom.) Normally, I just use one. If the GH doors are closed, the clamp is on. I know Martha Stewart would have a prettier solution, but she's not here.

A side note about doors in cold climates (added 12-16-08.) Although not a problem for me, some Harbor Freight owners have posted that the sliding doors have a nasty habit of freezing closed in cold wet weather. Some say this is made worse by the addition of a rubber gasket (as I applied on mine, above.) Others say the ice accumulates in the lower track. If you live in a cold climate, it's not a bad idea to think which side panel you might remove for emergency access to the greenhouse interior, if the doors freeze shut in a bad storm.

Several people have eventually removed the sliding doors and modified the front of the greenhouse to accept a hinged storm door, which seems to solve the problem. To see photos of what others have done, you can visit these threads from the Gardenweb greenhouse forum:

Modifying sliding doors to a hinged door
Modifying sliding doors to a hinged door

Okay, enough door fiddling. Now you can click here to go to the really important section, Part Five, Modifying the Greenhouse Frame for Strength!