Too long span floor joists?

[Le JG]

Hi, I am renovating a house from 1935 and am currently installing new floor joists. I'm now about to lay joists above the basement where the longest span is 4400mm. I am building the joists with 45x220 C24 cc400, can this work or is the span too long? I recall that the limit for what's considered "okay" starts at 4 meters for that spacing and dimension of the timber.

If it's too long, there's 3 meters across to break the span, but I don't have the option to lower the ceiling level, so I would need to recess maybe a HEA or IPE steel beam. What dimension would be reasonable in that case? Or could I manage with 45x220 across and attach the supporting beams with hangers? Perhaps a thicker glulam beam 70x220, to which I can then attach the main beam with hangers? There will be a kitchen in this space; I don't know if that makes a difference, but the kitchen will be installed right by one of the supports, so the "middle" of the span is essentially an "empty" floor area in the kitchen.

Grateful for any tips.

 

[Anonymiserad 23608]

45x220 works as you have in mind at 4400 if you have 22 mm screw-glued particleboard on top.

 

[Anonymiserad 405730]

Cross-staff is needed more often than not!

 

[Le JG]

Hello, thanks for the response. I forgot to mention that I previously installed kortlingar. Krysskolvning is somewhat similar, if not a bit more efficient? There will be floorboards on top, so unfortunately no chipboard to stiffen.

 

[Anonymiserad 405730]

Hi, thanks for the response. I forgot to mention that I previously laid kortlingar. Krysskolvning is somewhat similar if not a bit more effective? There will be floorboards on top, so unfortunately no particle board to stiffen it.

Yes, it's just as good to have whole pieces as krysskolvning, not many people use diagonal bracing anymore, it's not time-efficient.

 

[Anonymiserad 23608]

There will be floorboards on top so unfortunately no chipboard to stiffen it up.

Then the recommendation is a maximum of 4150 mm. However, I would go with 45x220 and cross-lat properly. This creates interaction between the beams and stiffens it up properly, so I don't think it will feel wobbly.

Otherwise, you have to step up to 45x245 which can handle 4640 mm.

 

[Le JG]

Thank you for the great answers!

Then the recommendation is a maximum of 4150 mm. However, I would have gone with 45x220 and cross-battened properly. This creates interaction between the beams and stiffens it up significantly, so I don't think it will feel shaky.

Otherwise, you need to step up to 45x245 which handles 4640 mm.

Thank you!

 

[Le JG]

Then the recommendation is max 4150 mm. However, I would go with 45x220 and cross-batten properly. This provides interaction between the beams and significantly stiffens them, so I don't think it will feel wobbly.

Otherwise, you can step up to 45x245 which handles 4640 mm.

Yes, it works just as well to have entire pieces as cross-bracing; not many people use cross-bracing anymore since it's not time-efficient..

Thank you!

 

[AG A]

In my small cottage, I have a span of 5.7 meters, cc600. The floor is made up of the bottom of the truss. The floor joist is 45x145. The floor is just regular tongue and groove floorboards. There is absolutely no sign of flex or sagging.
There was supposed to be a load-bearing wall on the lower floor, but the tenant really wanted an open floor plan. When I noticed how stable it was, we left it that way.
I don't advise going under 45x220. But I can say that you can be more than calm regarding stability.

 

[Oldboy]

It sounds like a miracle.

The loft of our garage has a floor structure with 48x175, cc 60 cm, over a span of 585 cm. The floor is 21x95 plank. In the middle underneath, there is no load-bearing wall, but a 100x200 solid wood beam over a span of 540 cm. It sways when you walk on it.
However, the structure has managed a load of approximately 4.5 tons of hay over 66 m². That equates to about 45 guys in the deciton club...