Floor sagging as someone cut through beam

14 Jan 2009
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United Kingdom
The dinning room floor in our new house is sinking but I have access to underneath via the cellar. Floor is 4m by 4m and supported by 4x2 joists! The problem is that the previous owners decided to replace the sleeper wall running along the middle of the span with a 5x3 timber beam going the entire 4m length, this may have sufficed but a section of the beam was then cut out (presumably to make headroom in cellar) and now the whole floor is sagging.

It will only get worse so I need to fix it, I can either build a new sleeper wall or replace the broken 5x3 beam with new one. I'm not convinced that the original timber 5x3 beam is strong enough and my preference is to replace it with a 4m 5x3 steel beam, does anyone know if this will be ok, a bigger beam would be much harder to fit as 5x3 wil just slot straight in?
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2m span is ok for 4X2" joists.

the 5x3" timber beam however was woefully inadequate.

i doubt that there is steel beam suitable at 5" deep. you may need something in the realms of 6-7" deep.

shytalks will no more...... ;)
152x89UB16 tight up under joists with an engineer brick padstone each end.



(And can you believe I just used a calculator to do 1.5x4/2 ffs!)
If you're a bit tight for headroom, notch an inch (max) out of the joists, before installing the beam. 4x2C16 at 400 with a 25 notch fail slightly on deflection with a point load, but don't worry about that, the notching won't affect that. If the floor's a tad bouncy, put some solid noggins at midspan either side of the beam to stiffen it up. Nog between the joists over the beam as well.
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Thanks for the help, the floor is definately sloping and quite bouncy, although I should probably stop 'bounce tests' immediately! I think I'll get the wall rebuilt, I can put a concrete lintel in the middle to have access to the other half of the cellar.
Put some acrows underneath and wind them up before you either rebuild or put a beam in. That way you can take some of the sag out.

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