We are building a greenhouse and have laid and built the foundation according to proper standards. About 10+2 meters long (the first 10 meters is the greenhouse and then 2 meters is a storage room) and 4.5 meters wide.
The roof will be tempered glass about 3-4 mm thick.
But I'm uncertain about the dimension of the ridge beam. It's a relatively light roof (I believe all the glass weighs about 300-400 kg) with a slope of about 33 degrees (so any snow will slide off, and there hasn't been snow here for a day in the past 5 years, for that matter). I have looked at some tables, but then I get astronomically thick glulam beams to handle a 10-meter span.
Does anyone dare to make an educated guess on a glulam beam to use? Preferably without a post in the middle of the greenhouse, but in an emergency, we can place a post in the middle.
Grateful for a bit of help and encouragement as we're a bit stuck on the glulam point right now.
The roof will be tempered glass about 3-4 mm thick.
But I'm uncertain about the dimension of the ridge beam. It's a relatively light roof (I believe all the glass weighs about 300-400 kg) with a slope of about 33 degrees (so any snow will slide off, and there hasn't been snow here for a day in the past 5 years, for that matter). I have looked at some tables, but then I get astronomically thick glulam beams to handle a 10-meter span.
Does anyone dare to make an educated guess on a glulam beam to use? Preferably without a post in the middle of the greenhouse, but in an emergency, we can place a post in the middle.
Grateful for a bit of help and encouragement as we're a bit stuck on the glulam point right now.
Hello,
Assuming the glass weighs 10 kg/m2 (I googled 2.5 kg/m2 and mm, correct me if I'm wrong
) and then there would be some kind of aluminum profile or similar to secure the glass in place, and you might want to hang something from the beam. If we then consider 25 kg/m2 for the roof, we get about 60 kg/m on the glulam beam.
This can be handled easily by a 315x90 (GL30c), for instance, but the issue I see is deflection since I believe greenhouses fall under climate class 3 - which is quite unfavorable compared to climate class 2. Glass is not known for withstanding large deformations, so it's important that it can handle the flexing of the glulam beam - is there anything in any product sheet or similar for the glass roof that states what it can withstand?
A 405x90 would result in about 2 cm deflection in the short term (which could be built out) - in the long term this increases to about 3 cm, which is around L/300, usually a common guideline, but that's for roofs not sensitive to deformations.
So the question is what the glass can withstand.
I have now calculated with only permanent load, which is of course advantageous.
Assuming the glass weighs 10 kg/m2 (I googled 2.5 kg/m2 and mm, correct me if I'm wrong
) and then there would be some kind of aluminum profile or similar to secure the glass in place, and you might want to hang something from the beam. If we then consider 25 kg/m2 for the roof, we get about 60 kg/m on the glulam beam.This can be handled easily by a 315x90 (GL30c), for instance, but the issue I see is deflection since I believe greenhouses fall under climate class 3 - which is quite unfavorable compared to climate class 2. Glass is not known for withstanding large deformations, so it's important that it can handle the flexing of the glulam beam - is there anything in any product sheet or similar for the glass roof that states what it can withstand?
A 405x90 would result in about 2 cm deflection in the short term (which could be built out) - in the long term this increases to about 3 cm, which is around L/300, usually a common guideline, but that's for roofs not sensitive to deformations.
So the question is what the glass can withstand.
I have now calculated with only permanent load, which is of course advantageous.
There is zero data on the glass. Purchase of some remainder stock on the marketplace. Tempered glass panes about 50x70 cm. The weight of about 10 kg/m2 sounds about right.
The idea is to attach studs to the ridge beam and slope them down towards the walls. I'm thinking of using something like 45x95 or 45x120 for the studs. We don't yet know how the glass will be attached, but either with some molding or with putty.
We are currently looking at 360x90 or 404x90. Deflection is clearly a problem, especially if it changes over time...
The idea is to attach studs to the ridge beam and slope them down towards the walls. I'm thinking of using something like 45x95 or 45x120 for the studs. We don't yet know how the glass will be attached, but either with some molding or with putty.
We are currently looking at 360x90 or 404x90. Deflection is clearly a problem, especially if it changes over time...
Last edited:
The rules naturally depend on the distance between, but assuming cc1200, 45x120 roughly meets the same deflection requirements - although I haven't included any normal force, but there's an option to adjust a bit there as well if needed (4 kN).
How should the greenhouse be stabilized?
How should the greenhouse be stabilized?
I have measured the glass for the ceiling now, and they are 100x56 cm. I plan to set the studs with a 60 cm center-to-center distance and then place the glass on them, 3 in "height." Maybe using 70x70 studs could also provide a better bearing surface to place the glass on. They won't carry much weight, I'm mostly concerned about the mounting of the glass on that part, but that's for later and will probably need to be solved on-site.
I've been thinking about installing a cross brace in each half of the ceiling for stability. Maybe with a wire. Perhaps along the long side as well.
But if you were to use a 360x90 or 405x90 glulam, don't you think it sounds feasible with a 10 m span?
I've been thinking about installing a cross brace in each half of the ceiling for stability. Maybe with a wire. Perhaps along the long side as well.
But if you were to use a 360x90 or 405x90 glulam, don't you think it sounds feasible with a 10 m span?
Had forgotten to include the angle when I was calculating 45x120, so I calculated the beam too short, but with cc600 it still works (and then can handle 3 kN in compression). However, 70x70 won't work as a replacement — you need double 45x95 (double 70x70 won't work either).
Yes, with the assumed load, there are no problems — I would have chosen 405x90. It will hold, but the question mark still remains regarding deflection and how sensitive the glass might be (and if it becomes as "bad" as climate class 3). I don't have direct experience with any benchmarks for either greenhouses or the glass, maybe someone else knows?
Wire sounds convenient, I think it's important to secure the attachment so that it doesn't come loose in strong winds and can be tightened enough to be rigid. Wire can only handle tensile force, so in that case, I would think there would be greater compressive force in the roof beams than if it's possible to use bracing (which can handle both compression and tension).
I haven't calculated the potential force from the wind, it also depends on wall height, location, and surrounding terrain — but I don't really have the opportunity to look into that part.
Yes, with the assumed load, there are no problems — I would have chosen 405x90. It will hold, but the question mark still remains regarding deflection and how sensitive the glass might be (and if it becomes as "bad" as climate class 3). I don't have direct experience with any benchmarks for either greenhouses or the glass, maybe someone else knows?
Wire sounds convenient, I think it's important to secure the attachment so that it doesn't come loose in strong winds and can be tightened enough to be rigid. Wire can only handle tensile force, so in that case, I would think there would be greater compressive force in the roof beams than if it's possible to use bracing (which can handle both compression and tension).
I haven't calculated the potential force from the wind, it also depends on wall height, location, and surrounding terrain — but I don't really have the opportunity to look into that part.
It's windy! Located on the west coast and open.
While we're at it and sizing beams, the second top plate on the walls on the long side is indeed the berliner. There, the glass is 1200mm wide with vertical studs of 120*95. Is it enough with a top plate of 120, or should we go up a size on that? I have, for example, 170mm at home. (It just becomes so bulky at the eaves with that...)
While we're at it and sizing beams, the second top plate on the walls on the long side is indeed the berliner. There, the glass is 1200mm wide with vertical studs of 120*95. Is it enough with a top plate of 120, or should we go up a size on that? I have, for example, 170mm at home. (It just becomes so bulky at the eaves with that...)
I think one should be quite strict when it comes to the deflection of such long beams. L/300 over 10m is still closer to 33mm, which will also be clearly visible. I would limit the deflection to ~15mm, then the angle change will be so small that you don't have to worry about the glass. As mentioned, it will result in grotesque dimensions, so I would recommend a bearing point in the middle of the beam. Then you hardly need to check the deflection. The bearing point can, for example, be a column down to the ground. If you don't want a column in the way, it can be solved with a type of frame construction.
Unfortunately, I have to revise my glulam beam, just noticed I forgot to switch back to climate class 3 when comparing results (not easy to run Excel via mobile )
For L/300, a 115x450 is required (90x405 was for climate class 2).
To limit to 15 mm in the long term, a 115x630 is required, pretty substantial in other words!
Some kind of support might not be a bad idea.
)For L/300, a 115x450 is required (90x405 was for climate class 2).
To limit to 15 mm in the long term, a 115x630 is required, pretty substantial in other words!
Some kind of support might not be a bad idea.
Yes, 115x630 was what I had derived in my calculations. It felt astronomically large, and I hoped it was based on a heavier roof. It simply must have a pillar in the middle...
My second question related to this was about the top bearer on the side walls. The idea is to place a 170x45 beam there, with the posts spaced at 1240mm center-to-center. reasonable?
Regarding other questions, it is by the coast but not in sea spray or similar, quite a bit away from the sea. But windy. ;-/
The side walls are on a mire, 60 cm high, and the roof pitch height will be about 2300mm. Ridge height approximately 3800mm.
The house will be oriented with the gable in the windiest direction.
My second question related to this was about the top bearer on the side walls. The idea is to place a 170x45 beam there, with the posts spaced at 1240mm center-to-center. reasonable?
Regarding other questions, it is by the coast but not in sea spray or similar, quite a bit away from the sea. But windy. ;-/
The side walls are on a mire, 60 cm high, and the roof pitch height will be about 2300mm. Ridge height approximately 3800mm.
The house will be oriented with the gable in the windiest direction.
Hope someone else can weigh in about the beam, I find it hard to comment on it without a bigger effort (haven't sized before). But I believe you usually place a post where the roof joists land, but it might be fine in this case considering it's quite a small load.
The horizontal joist will help handle the wind, but it works together with both the roof and the rest of the wall, so it might be okay. However, I'm not confident enough to give an approval there—so hopefully someone else can assist with that as well.
Good luck with the construction!
The horizontal joist will help handle the wind, but it works together with both the roof and the rest of the wall, so it might be okay. However, I'm not confident enough to give an approval there—so hopefully someone else can assist with that as well.
Good luck with the construction!
Yes, many thanks for that, I received support for a couple of decisions. We will go with a 170mm bärlina in the wall. Then we will brace up in all possible places. The gavlarna and the post will take most of the roof's load, I think. So it should work out well in the end...
Hi.
I'm working on a nearly identical build (10x5m) and have also concluded that it's an unnecessarily strong beam with a 10m span. So there will likely be a post in the middle.
Have you thought about how much the roof structure will push the walls outward? I was considering tensioning wires between the walls.
Do you have any drawings that you'd like to share? I'm starting to draft the construction tomorrow.
I'm working on a nearly identical build (10x5m)
and have also concluded that it's an unnecessarily strong beam with a 10m span. So there will likely be a post in the middle.Have you thought about how much the roof structure will push the walls outward? I was considering tensioning wires between the walls.
Do you have any drawings that you'd like to share? I'm starting to draft the construction tomorrow.