greenhouse Archives - Garden and Stuff

Greenhouse Roof Replacement 2024

Joyce Gross greenhouse January 4, 2025January 13, 2025

In the fall of 2024, after years of becoming increasingly leaky, the glass roof of the greenhouse was replaced with a twin wall polycarbonate roof. It took two months, not counting the years I spent figuring out how to actually do it (and wishing it were possible to keep the glass roof).

The caulk and butyl tape that kept the glass panes of the original roof in place made the roof difficult to maintain. The panes would slip a quarter of an inch, an inch, or a foot, leaving gaps for rain to pour into the greenhouse. To fix one slipped pane required unsealing and resealing not just one pane but between two and eight panes. One would think that if they are slipping it would be easy to get them off to reseal, but NO, that was not the case. While the caulk and butyl tape did lose their sealing powers after a few decades, it was only in a few spots. The rest of the caulk and tape stuck so well to the wood and glass that it was very hard to move the glass without breaking it. I decided that the only way to keep the greenhouse functional and prevent it from falling apart was to get rid of the glass roof.

Twin wall polycarbonate panels are used often on greenhouses now. They do not require caulk and are long-lasting. (Too long, if you don’t want to be contributing to the world’s microplastic problem.) The trick for me was figuring out how exactly to cut the polycarbonate panels for my particular roof that had specifically been made to hold glass panes and that had two different slopes and also six large, openable windows.

The good news is that once the glass, caulk, and butyl tape were removed, the rest of the roof — the wood frame — was in nearly perfect condition and very sturdy. I’m sure the frame breathed a sigh of relief to have the much lighter-weight polycarbonate on it instead of the heavier glass panes.

During most rains now, there are no leaks at all inside the greenhouse. It’s completely dry! During very heavy rains with wind, a small amount of water splashes into the greenhouse in a few places, not enough to be a problem. It is a greenhouse after all — I splash more water around when I water my plants.

Here are photos from the roof work:

Greenhouse roof in 2014, freshly painted. Unfortunately in the subsequent 10 years, the paint and wood condition deteriorated with age and weather. Worse, many of the glass panes slipped, causing leaks everywhere inside the greenhouse when it rained.

Sept 8, 2024. Official start of roof replacement. In this photo one of the six roof windows has been taken off and one pane has been removed. The other pane slipped out on its own a couple of years ago.

Some of the wood was in bad condition.

Another view of the roof before it was replaced. The missing pane half slipped out many years ago. I managed to pull it the rest of the way out a year or so ago.

Two slipped panes. There were 8-10 slipped panes by 2024.

One of the windows/vents. The wood has seen better days.

The same window, closer up.

Two strips of wood on the upper slope removed. The glass panes are still well-seated in butyl tape and caulk. Most of the time it was a struggle to get them out -- but much easier if you didn't mind if they broke during the process. Only 20% of the panes came off unbroken.

This is one of the 2x2s that makes up the roof rafters and that supported the glass. The glass was attached on its bottom side to the 2x2 with butyl tape and caulk, and on the top with more butyl tape and caulk to the thin strips of wood.

One of the piles of butyl tape, caulk, and broken glass from the old roof.

Some of the nails from the old roof. I finally got my tetanus booster while working on this roof replacement -- it had been 24 years since my last one.

Piles of broken glass and wood from the roof.

Removing glass from the old roof.

Glass removal in progress.

A lot of caulk and glass fell to the floor while removing the roof.

Glass removal in progress.

One half of the old roof completely removed.

Half of the old roof gone.

The windows were cleaned up in the garage. Some wood was replaced and quite a few pieces were patched with two part wood epoxy.

Bending the window flashing without a brake (tool for bending metal) was tricky but I got it done.

Cutting the twin wall polycarbonate. The cat is helping.

The polycarbonate for the windows was the first to be cut and attached. Note that the rafters have also been painted, at least the parts that would be difficult or impossible to paint once the roof is on.

Measure measure measure. Even after dark.

The twin wall polycarbonate panels drying after being cut with the jigsaw and then hosed to remove little bits of plastic.

The first half of the roof is half done.

Half the roof is done.

View of the polycarbonate roof from inside the greenhouse.

The completed first side. I did have to take the three windows off one more time later to put on the metal flashing and add more screws. Also, the metal flashing that goes on the peak is not attached yet -- that had to wait until everything was done.

One side done.

The second side now has all the glass, caulk, and butyl tape removed.

The second side has been painted.

View from inside the greenhouse. One side of the roof is completely open; the other side has the new polycarbonate roof.

Putting on the last panels.

Finally it's finished! The metal peak is back on. Metal flashing has been attached to each of the six windows. New vent openers were installed and the windows all open on their own on warm days.

Close-up of one of the windows in the open position.

Close-up of one of the windows. The metal flashing made all the difference with rain not getting in on stormy days.

Windows open on a warm day.

Part of the floor was brick until now. I reused the old bricks and added new ones to cover the whole floor. Note the dirty walls on the left. This is from when the roof leaked and rain splashed down on the dirt and splattered mud on the walls.

The new floor is finished. The walls have been cleaned up.

The rest of the wood making up the roof support is painted now. The next photos show views of the newly-painted rafters.

Newly painted roof rafters.

Another view of the roof rafters.

Another view of the roof rafters.

Another view of the roof rafters.

Everything complete... aside from some leaks in the vertical glass panes which will no doubt keep me busy for the rest of my life.

Greenhouse with new roof. Roof windows partially open.

More of the crazy rafters.

New twin wall polycarbonate roof with old rafters freshly painted.

More of the crazy rafters, different lighting than before.

Greenhouse roof replacement finished.

Inside the greenhouse with the lights on and cat looking out a lower window.

The Greenhouse Roof Repair Goddess. She keeps in our memories broken glass, old butyl tape and caulk, rusty screws, and rotting wood. Also twin wall polycarbonate, vent tape and U-profiles, metal flashing, and bricks.

Greenhouse Wall Repair 2021

Joyce Gross greenhouse January 2, 2025January 5, 2025

In the fall of 2021, I partially copied what Michael McGee did in 2014 to repair one side of the greenhouse. Seven years after his repairs, the wood on the other side, too, had a lot of rot.

Between the two 4″x4″ corner posts on the long sides of the greenhouse, there are eleven vertical 2″x3″ supports that go from the ground to the roof. Six of these supports had bad rot and half of those six were no longer providing any support whatsoever to that wall.

There were also rotted boards that needed replacing in various locations around the sides of the greenhouse.

To start, we built a 2″x4″ structure to help support the roof while I was doing the work. Whether it was needed or not I don’t know since some of the supports along that wall were still ok….

The most complicated and worrisome part of this project was that the 16′ x 2″ x 6″ board that goes all the way across the length of the greenhouse just below the glass windows was especially rotted. That board was cut very specifically for my greenhouse and it was impossible for me to replace. So my goal was 1) to replace the parts of the vertical supports that were rotted, and 2) to repair the 16′ board from the inside as much as possible, then cover the mess with new wood.

A third goal was to keep water out of that wall in the future. I’m still working on that. 🙁

This is the wall before repair started in the fall of 2021. One of the vertical supports is completely rotted away below the bottom row of windows. Five of the other supports are in various degrees of rot.

Closer up. Note that where one of the 2"x3" supports is missing, the board above it is gone as well -- from rot. That horizontal board is actually part of the 2"x6" that goes all along the greenhouse and protrudes on the outside. The outside surface is nearly flat and does not drain water very well. I think water also seeped in through the window sills.

The temporary support structure.

I removed six of the cedar boards between the windows along the bottom wall. They had rot and needed replacing.

I used a lot of two part wood epoxy to fill in areas where wood had rotted.

The big problem with this area was that it was open to the outside -- the wood that was supposed to prevent that was gone from rot. Water seeping down the inside wall had done damage to the inside wall too. In some cases I replaced the wood, or if the damage wasn't too horrible I patched it.

More two part epoxy wood patch.

Rebuilding 2"x3" boards with two part epoxy wood patch.

Rebuilding 2"x3" boards with two part epoxy wood patch. It takes a few iterations to make corners.

I used to like working with clay when I was a kid.

Having six out of eleven of the vertical supports out, even with the 2"x4" frame to support the roof, made me nervous. I always had one or two other temporary supports rigged up at the same time. One day there was an earthquake and the greenhouse didn't even rattle.

New shiplap cedar siding.

This is the section where the 2"x6" that goes around the whole greenhouse was not so damaged. I added a new 2"x3" board under it and attached two new supports. The original supports, when the greenhouse was built, went from the ground to the roof in one piece. Now six of them on this side are in two pieces.

This section was more of a mess because the 2"x6" was more rotted.

A view of the two sections, one finished, one not.

Getting ready to put in the last four supports.

Looking again at the finished part...

The last four supports are in place, along with the triple row of what looks like 2"x3"s, but the middle layer is the 2"x6" and I had to carve out chunks of a 2"x3" to make it fit and look as if it was really the inside edge of the 2"x6".

All the rot of that 2"x6" is hidden now.....

The second set of cedar shiplap boards have been installed, replacing older rotting boards.

All repairs finished!

Wall repairs finished. Wall cleaned and painted.

Wide angle shot of whole interior. See the slipped glass pane in the upper right of the image? That got fixed in 2024.

Shiny, clean wall with no sign of wood rot. Six new cedar boards, six new 2"x3" supports, lots and lots of wood epoxy, and a triple layer of 2"x3"s that wasn't there before, under the windows.

This is the outside of the repaired wall. The ledge under the windows is the 16' long 2"x6" that had a tremendous amount of rot in places.

A relief to one's eyes after all the photos of the rot.

Must take photos while everything is so clean and the paint fresh.

I began prepping the roof rafters for painting, too, but didn't get around to painting them until 2024.

I replaced rotted wood in a few other places on the greenhouse at the same time I was doing the other work. Here's a board with rot at one end, near the door. I cut off the rotted end of the board and used the good end to replace rot in the wall on the other side of the greenhouse.

New board where rotted one was, near greenhouse door.

This corner has a huge and scary amount of rot. It is not just the siding, but also the 4"x4" vertical support. I replaced two of the side pieces and sealed the corner trim with new caulk but did not do much about that 4"x4"... at least not yet.

Rot!

I replaced this board.

Endless....

Looks as good as new now!

This angle too!

The corner trim reattached and recaulked.

This corner got recaulked as well.

These are replacements for the strips of wood that are above and below each pane on the greenhouse sides. I replaced ten that were on the south side and in poor condition. The two pieces on the left were the originals.

Another corner recaulked.

Everything put back together. Three years later the roof replacement began.

Greenhouse Images 2015-2018

Joyce Gross garden, greenhouse January 22, 2018January 4, 2025

The greenhouse in my backyard was built by architect Michael Cobb, who grew up on the property behind mine. Read Michael’s blog for a history of the building of the greenhouse.

[Show slideshow]

Greenhouse Work 2014

Joyce Gross garden, greenhouse January 22, 2018January 4, 2025

In the summer of 2014, Michael McGee agreed to tackle repairs on my greenhouse. The supports along one side of the structure were rotting, along with many of the boards to which the supports were attached. Michael did an amazing job.

After Michael’s repairs, I wanted to paint the entire greenhouse. Not only did the new wood need painting, but much of the paint on the old wood was gone or peeling. There had been a partial repainting many years ago, but that paint was not in great shape either.

The greenhouse has 200 windows. The prepping took more time than the painting. This was a big, slow job. One layer of primer + two layers of paint = 600 windows to paint.

The greenhouse was built by architect Michael Cobb for the previous owner of my house. Michael grew up on the property behind mine. Read Michael’s blog for a history of the building of the greenhouse.

[Show slideshow]