Building a self-supporting greenhouse with polycarbonate

[Tyresö]

Already sitting with thoughts on spring projects.

For those of you with experience with twin-wall polycarbonate, is it technically possible to build a self-supporting greenhouse with, for example, 10 - 15 mm twin-wall polycarbonate (walls and ridge roof)?

Will the aluminum profiles used to frame the twin-wall polycarbonate have enough load-bearing capacity (standing walls) to support a snow-laden roof? Or must you first build an aluminum profile frame, which is then clad with twin-wall polycarbonate?

Please come with suggestions and ideas on how I should complete the project.

The reason I don't want to buy a ready-made greenhouse is:

* With twin-wall polycarbonate, I can decide the wall dimensions myself - both height and width.
* The insulation will be much better than in ready-made greenhouses (6 mm twin-wall polycarbonate).
* The building price/m2 of the greenhouse will be cheaper than a ready-made greenhouse.
* The most important reason: The joy of being able to implement your ideas and see the results! (On this point, everyone on the forum is the same)

Of course, I will use my concrete pump to pump concrete to the insulated concrete slab that I will cast, which the greenhouse will stand on (no need for concrete and casting tips).

Those with experience with twin-wall polycarbonate, please share your suggestions...

 

[Tyresö]

I know that building a greenhouse is not that impressive - it's for my wife who is going to grow her plants and herbs.

But there must at least be someone on the forum who has installed a polycarbonate roof, and has an opinion on the strength and stability of polycarbonate sheets framed with the aluminum strip that comes with it.

 

[magnu]

I have installed a corrugated plastic roof on wooden beams, it's still up.

However, I'm a bit unsure about the corrugated plastic itself, I have a feeling it might warp.

I recall that we cut off a few pieces and they became quite crooked after a while. This in itself isn't a problem when you have a frame construction like we did.

 

[Tyresö]

Then maybe I should build a frame with an alu-profile?

 

[Helioz]

I have built a roof with 16mm multi-wall polycarbonate from Skånska Byggvaror, and I wouldn't dare to use their system without a supporting timber frame. The panels themselves are sensitive to impacts, and the aluminum profiles that come with it are of weak dimensions. I built with their recommended size for glulam beams, which is 56x180mm at 1070mm center-to-center, and I added cross supports at 600mm center-to-center with 45x70mm beams. It became very stable, but you still can't walk directly on the roof without using a load-distributing sheet.

It might be difficult to use an aluminum frame because the multi-wall polycarbonate systems are designed to be mounted on wooden beams; in my case, they only fit 56mm wide glulam beams. Also, note that the cheapest manufacturers sometimes don't have completely transparent multi-wall polycarbonate, which is most suitable for greenhouses. Their plastic is opal white, as it is called, and does not let through all sunlight; you can't see through it. It may also be difficult to make penetrations in the plastic for ventilation systems and such since condensation can form in it, which must be able to drain out.

Otherwise, I think the idea is good; it can be different and cool with multi-wall polycarbonate in both walls and roof. I would go for a white-painted (the panels shouldn't rest on dark materials, as they can become discolored from sun bleaching) timber frame to simplify the installation of the panels and for stability. I wouldn't build with less than 16mm thickness on the plastic; even that felt on the border before I added cross supports at 600mm center-to-center. If you choose 40mm thickness, you can save on beams as the panels are mounted at 1240mm center-to-center instead of 1070mm for the thinner ones.

One tip is to read the different manufacturers’ installation guides for multi-wall polycarbonate panels so you can better form an idea of how they should be set up. There is quite a bit of work with pre-drilling, taping, rubber strips, and such before you can mount the panels. Here is the guide from Skånska Byggvaror, for example:
http://www.skanskabyggvaror.se/media/pdm/filer/Kanalplasttak%20100329_low.pdf

 

[Tyresö]

I have built a roof with 16mm polycarbonate from Skånska Byggvaror, and I wouldn't dare to have their system self-supporting without a wooden frame. The sheets themselves are sensitive to impacts, and the aluminum profiles that come with them are of weak dimensions. I built with their recommended dimensions on glulam beams, which are 56x180mm on cc1070mm, and I also put cross braces on cc600mm with 45x70 beams. It became very stable, but you still can't walk directly on the roof without using a load-distributing board.

It would probably be difficult to use an aluminum frame because the polycarbonate systems are built to be mounted on wooden beams; in my case, they only fit on 56mm wide glulam beams. Also, consider that the cheapest manufacturers sometimes don't have completely translucent polycarbonate, which is best suited for greenhouses. Their plastic is opal white, as it's called, and doesn't let all sunlight through, and you can't see out through it. It can also be difficult to make penetrations in the plastic for ventilation systems and such, as condensation water forms in it, which must be able to drain out.

The idea is otherwise good, I think, it can be different and cool with polycarbonate in both walls and roof. I would go for a white-painted (the sheets must not rest on dark materials, they can become discolored by sun bleaching) wooden frame to simplify the installation of the sheets and for stability. I wouldn't build with less than a 16mm dimension on the plastic; even that felt on the edge before I put cross braces on cc600mm. If you choose a 40mm dimension, you can save on beams as the sheets are mounted on cc1240mm instead of cc1070mm on the weaker ones.

A tip is to read through the different manufacturers' installation guides for the polycarbonate sheets so you can better understand how they should be set up. There's quite a bit of fiddling with pre-drilling, taping, rubber strips, and such before you can mount the sheets. Here is the guide from Skånska Byggvaror, for example:
[link]

Thanks a lot for the information!
My wife has explained that the polycarbonate not being clear, but milky white, is an advantage for some reason.....

Another point of using polycarbonate is that it's a building material, which allows me to make an economic deal with the tax agency via my company. But if glulam beams are needed to support the construction...then the point of my deal with the tax agency disappears....

It then looks like it will have to be a completely ordinary mass-produced greenhouse instead.
I won't back down, my wife will get a greenhouse tailored to her requirements (insulation requirements come before design or color). Too bad the mass-produced greenhouses only have 6 mm polycarbonate—a significantly lower insulation than my wife requires.
Of course, my wife, like all other wives (that's what she's called when she's not peering over my shoulder), has 100 explanations for why a Gucci handbag is better than a Fristads or Snickers tool belt.

The difference with my wife (a nurse) is that she has independently calculated the optimal U-value/heating cost for her potted plants...or whatever she's growing. Ideally, the greenhouse should have a U-value below 2.0 - preferably lower....
A mass-produced greenhouse with 6 mm polycarbonate??? Try manufacturing greenhouses for the Swedish market with 10 - 15 mm polycarbonate!

I run a concrete pumping company that transports, pumps, and pours concrete + formwork and reinforcement!

I can offer my wife the optimal concrete slab with extreme insulation (40 cm of styrofoam) and recesses in the slab for hardy plants and cast raised beds that are insulated and cast in customized (the wife's) Miljas formwork imprint and pigmented terracotta concrete—in addition to a concrete quality that Öresund Bridge is cast in (there's no higher class and requirement for concrete) except that we use only 0-8 fractions that I pump up to the slab.

But... I can't find a greenhouse on the market that matches such a super concrete slab and meets the equivalent insulation requirement of 2.0 or lower.

Are there others on the forum with high demands on greenhouses?

 

[Krawk]

The obvious choice here is, of course, to continue with the concrete and cast the frame for the greenhouse!

 

[saturnus]

Are there more people on the forum who set high standards for greenhouses?

Yes, I do, but there aren't many others in real life.

If you search for greenhouses, there are some posts from me, among others. I haven't read through the above posts thoroughly, but something to consider is having a concrete slab or concrete paths, which means it becomes very dry in the greenhouse if it's going to be used for cultivation. Then you have to water the floor many times a day during the summer.

The idea that a greenhouse would be a flimsy building, I do not agree with, greenhouses are built for their purpose and work well even in storms, where other sturdier buildings get damaged.

Since nothing is impossible, it might also be possible to create a free-standing greenhouse with cellular plastic. But how do you manage the eaves = the junction between the roof and the wall, and what should it stand on? It hardly works to bury the panels in the ground. I think it would take too long to figure out solutions around such a construction, rather than building with a frame. The cellular plastic is 1200mm wide, if you want to keep this width, you need a sturdy frame to keep it in place. If you're going to have a greenhouse, I think it should resemble a greenhouse. It's also possible to build one against a wall, with one half being a roof and the other a wall. Remember that wider glass or panels result in a weaker construction. My own little greenhouse is built with glass measurements from the 1920s-30s, = 380mm, the door and ventilation system are also from this time, so the house is built in an old style. If you're worried about snow loads, you can have a slightly higher pitch on the roof.

 

[Tyresö]

The obvious choice here would obviously be to continue with the concrete and cast the frame for the greenhouse!

Have thought about it, but it seems like overkill to build a greenhouse. Then there will be a lot of formwork/reinforcement work and insulation work to cover the concrete so it doesn't become a cold bridge.

The advantage of building it in concrete is the stability.