Hello
I am planning to decorate the attic of the garage and will therefore need to modify the roof trusses.
In the end, I might outsource both the calculation and the reconstruction, but I am still curious if there are any tools/calculation tools that, based on the existing drawings and dimensions of the W-trusses that are there today, can transform these strengths and data into a drawing for a suitable framework truss with more space in the middle for the room in the attic but that can handle the same loads.
Then, of course, I should review the existing load calculation since there will be floors and walls added, as well as a bed and some furniture on the upper floor, which might mean I should add a little extra to the new trusses.
Or is there anyone here in the forum who can help me, either with advice or professional help
I am planning to decorate the attic of the garage and will therefore need to modify the roof trusses.
In the end, I might outsource both the calculation and the reconstruction, but I am still curious if there are any tools/calculation tools that, based on the existing drawings and dimensions of the W-trusses that are there today, can transform these strengths and data into a drawing for a suitable framework truss with more space in the middle for the room in the attic but that can handle the same loads.
Then, of course, I should review the existing load calculation since there will be floors and walls added, as well as a bed and some furniture on the upper floor, which might mean I should add a little extra to the new trusses.
Or is there anyone here in the forum who can help me, either with advice or professional help
The consequences are usually unreasonable if the span is greater than 4-5 m. The truss replaces glulam and other structures for large spans.
Hello and thank you for your response.J justusandersson said:
The trusses need to be redone to remove the W-braces in the middle. But if I interpret your response correctly, you mean that the trusses cannot be reconstructed to support additional floor weight/attic when the span is so long... i.e. unreasonable.
As I understand it, I will most likely need a glulam beam or steel beam parallel to the trusses through the middle of the garage to halve the span and relieve the trusses.
It still seems to be the most likely solution. Glulam as flooring between the trusses will be far too expensive since the garage is 12m long.
In principle, it is necessary to build new roof trusses, even if you don't have to remove everything old. There is an obvious risk that the new attic floor will be quite tall. It doesn't have to be terribly expensive with glulam if the material is used correctly. However, a 12 m long steel beam in the middle of the garage will be expensive, probably at least 25,000 kr. For a more in-depth discussion, you need to know the dimensions of the garage.
The garage is 9.6m wide and 12.7m deep.
But how do you mean that glulam in the joists could be cheaper than 1 steel beam straight through the garage?
I was thinking of 1 steel beam straight through and then shortening the joists but seeing the rebuilt roof trusses.
10-11 9.6m glulam beams between existing roof trusses or as part of newly built trusses feel like a more expensive solution than 1 of 12.7m steel beam with 1-2 posts in the middle of the garage.
Glulam is quite expensive too, and it quickly exceeds 25k in the many lengths I need.
But how do you mean that glulam in the joists could be cheaper than 1 steel beam straight through the garage?
I was thinking of 1 steel beam straight through and then shortening the joists but seeing the rebuilt roof trusses.
10-11 9.6m glulam beams between existing roof trusses or as part of newly built trusses feel like a more expensive solution than 1 of 12.7m steel beam with 1-2 posts in the middle of the garage.
Glulam is quite expensive too, and it quickly exceeds 25k in the many lengths I need.
With those dimensions, it's more like 50K for a steel beam, which also gets unreasonable dimensions. This also applies to the glulam. The only chance is to accept columns in the middle or to limit the part of the attic that is used as living space, etc.
Oh, I didn't know that IPE beams were so expensive. My idea has been to use a 10m IPE beam and then finish the last 2.7m with a load-bearing wall since I have a room at the far end of the garage. But a 10m steel beam can't possibly cost 50k?J justusandersson said:
IPE beams are probably not the right type. They become very tall and unstable. It's more about HEA beams. But a 10 m beam needs at least one pillar in the middle to achieve reasonable dimensions.
Ok, that sounds very strange. I've read about several others here on the forum who have had 10m beams without any pillar underneath whatsoever.J justusandersson said:
And with a ceiling height of 3m in the garage, I should be able to go with an IPE beam of 300-340mm without problem.
How do you mean that the IPE beam becomes unstable? It is squeezed between the ceiling framework and 2-3 pillars standing on a concrete slab...they're not going anywhere. Where is the instability in the IPE beam?
Then of course, if I don't want to lower the ceiling height under the beam that much, I can of course switch to HEB or HEA, but then on the other hand I increase the self-weight significantly on the beam compared to IPE. Ceiling height is not a problem for me, and therefore I'm aiming for IPE.
But I might have to turn to a structural engineer this week and have them calculate it instead.
With a 10 m span, we're talking about an HEA 400. It weighs 125 kg/m which at 25 kr/kg including VAT amounts to 31,250 kr. An IPE beam with equivalent properties needs to be an IPE 500. It weighs 90.7 kg/m which costs 22,675 kr. An IPE beam is prone to lateral-torsional buckling due to its proportions, requiring special measures. Long steel beams can also be subjected to other force phenomena that require special consideration.
But even if you install a steel beam in the middle, the dimensions of the W-trusses' upper and lower chords are insufficient. With possibly 45x170 for the upper chords and 45x145 for the lower chords, you won't get far with the current span. Glulam will still be needed in several places.
But even if you install a steel beam in the middle, the dimensions of the W-trusses' upper and lower chords are insufficient. With possibly 45x170 for the upper chords and 45x145 for the lower chords, you won't get far with the current span. Glulam will still be needed in several places.
Ok, thanks for the info.. so it sounds like I simply need more columns.J justusandersson said:
As for the trusses, it's precisely the W-truss I don't want. I want to redesign them from W-trusses to framework trusses. But that also requires a truss factory to calculate... to modify the trusses and possibly beef them up.
I definitely think you should ask a truss factory. It is always good to have multiple inputs.
I think the best option would be to tear off the roof, put up the right kind of rafters, and lay the roof again. Reconstructing them is unreasonable.
How has it gone with this? I'd like to furnish a loft on our upper floor and have similar conditions in terms of dimensions and W-trusses. Right now it feels impossible to implement, and if we were to make a "proper" roof lift, the costs would skyrocket because it would be strange to only lift 1/3 of the roof, so we would need to do it on the whole house, and we are really only interested in making the children's rooms larger.