Feeling a bit uncertain as I sit and draft the plans for my floor structure since I've found some different "recommendations" for what dimension I should have.
The conditions are as follows:
Residence, 2 floors
Free span 4400 mm
Total beam length 4700 mm
c/c 600 mm
Subfloor 22mm screwed and glued chipboard.
I looked at the wood guide (run by Svenskt Trä) and there it says that 220*45 C24 can be used up to a free span of 4000 mm.
Then I found a PDF from Svenskt Trä that says the same timber can be used up to a free span of 4470 mm (up to 5210 mm c/c 300 mm) which would mean I can manage with 220*45 C24 in one case but not in the other...strange?
At one point I considered putting glulam beams in the floor structure, but it turns out it's even cheaper to put 220*45 C24 with c/c 300.
I will have 220*45 in the rest of the house but there the free span is only 3600 mm, so it would be nice to have the same dimension throughout the floor structure.
Anyone who knows or has experience building with these lengths, what should I choose for the floor structure?
http://www.svenskttra.se/MediaBinar...-4aab3517a0fa&MediaArchive_ForceDownload=true
The conditions are as follows:
Residence, 2 floors
Free span 4400 mm
Total beam length 4700 mm
c/c 600 mm
Subfloor 22mm screwed and glued chipboard.
I looked at the wood guide (run by Svenskt Trä) and there it says that 220*45 C24 can be used up to a free span of 4000 mm.
Then I found a PDF from Svenskt Trä that says the same timber can be used up to a free span of 4470 mm (up to 5210 mm c/c 300 mm) which would mean I can manage with 220*45 C24 in one case but not in the other...strange?
At one point I considered putting glulam beams in the floor structure, but it turns out it's even cheaper to put 220*45 C24 with c/c 300.
I will have 220*45 in the rest of the house but there the free span is only 3600 mm, so it would be nice to have the same dimension throughout the floor structure.
Anyone who knows or has experience building with these lengths, what should I choose for the floor structure?
http://www.svenskttra.se/MediaBinar...-4aab3517a0fa&MediaArchive_ForceDownload=true
Check out the beam software http://www.moelven.com/se/Produkter...ingsprogram/Dimensioneringsprogram/Lagerbalk/
It's not an exact science.Robert 75 said:
The maximum length (for a "normal load") is probably around there. The difference can be, for example, that they calculated on different load cases in the examples or maybe give different glued floorboards different contributions...
You could reinforce the flooring to achieve slightly better flex stability. We have 4200mm and 220x45 C24 and it became noticeably more stable after I glued and screwed reinforcement pieces.
4400 flooring with 220x45 at cc600 is definitely on the edge, you might expect that a slight flex will be noticeable. And you shouldn't tile any floor on that flooring.
I am absolutely not sure in any way, these are just my slightly unsubstantiated thoughts.
Indeed, that's true... also a comfort issue regarding how much deflection one accepts.Mikael_L said:It's not an exact science.
I have 3900 joists 220x45 today and know how it behaves...
Interesting to hear your experience and reasoning Mikael, thanks! d^_^b I've been considering screw-laminated blocking with c/c300 but it's a bit tricky to set up and takes time compared to glue-laminated timber.
What do you mean?Robert 75 said:
Joist in cc300 + noggins or noggins in cc300?
I don't think the latter makes much sense. One or two rows of noggins should be enough.
It's not particularly tricky to handle, at least if you have a miter saw that provides 90° cuts.
Sorry that I was unclear. I meant the first one, floor joists in cc 300, and was thinking of two noggings in each bay. By tricky, I meant getting access and screwing the noggings properly. I was considering a method where you make noggings out of, for example, floor chipboard that I found online, maybe a bit advanced :O
http://www.traguiden.se/TGtemplates/popup2spalt.aspx?id=4610&contextPage=5946
http://www.traguiden.se/TGtemplates/popup2spalt.aspx?id=4610&contextPage=5946
In post #76 you can see how I did it.
http://www.byggahus.se/forum/socialt-projekt/147204-kan-det-bli-nat-tro-3.html#76
Glued and screwed with 6x120mm. (I believe I predrilled with 4mm).
http://www.byggahus.se/forum/socialt-projekt/147204-kan-det-bli-nat-tro-3.html#76
Glued and screwed with 6x120mm. (I believe I predrilled with 4mm).
In my house, I have what's called cross-bracing in the joists, doesn't that make it more stable than just a nogging?
Cross-bracing only means more work and little saving of material, koltingar of the same dimensions as the floor joists, so it's the same thing but you avoid making crosses that must be exact if they are to be of any use.
The end result is that we will not be using 220x45 in the joists. We will be installing 250mm wood-based lightweight beams across the entire building structure (11.5m), which will then absorb the downward force (deflection) really well.
According to the builder, there would be TOO MUCH deflection with 220x45 beams, which is why he recommended lightweight beams.
According to the builder, there would be TOO MUCH deflection with 220x45 beams, which is why he recommended lightweight beams.
Good choice.
It's unfortunate with floors that are on the verge of being too shaky.
Might as well do it properly from the start.
It's unfortunate with floors that are on the verge of being too shaky.
Might as well do it properly from the start.
Construction veteran
· Åland
· 2 077 posts
Worked for many years in the wooden house industry, and normally 45x200 "övrigt virke" up to 360 cm and 45x220 up to 400 cm. This is due to requirements for tolerance and maximum deflection.
Kortling 2 pcs for length 400 cm and 1 pc in the middle for 360 cm span.
Kortling 2 pcs for length 400 cm and 1 pc in the middle for 360 cm span.
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Well, then there are new developments...
Since the supplier of the lightweight beams could not provide a quote (price and delivery date), it will now be a glulam joist consisting of 56x270. With the lightweight rule, we would also have needed to go up to 300mm. The advantage of glulam in our case is that it will be delivered together with the ridge beam and columns, which makes it easier as they will be 11.5 (beams) and 12.5 meters (ridge beam) respectively.
Since the supplier of the lightweight beams could not provide a quote (price and delivery date), it will now be a glulam joist consisting of 56x270. With the lightweight rule, we would also have needed to go up to 300mm. The advantage of glulam in our case is that it will be delivered together with the ridge beam and columns, which makes it easier as they will be 11.5 (beams) and 12.5 meters (ridge beam) respectively.