Stud partitions

[Magrah]

Hi, I have a couple of questions re the above and would not mind some opinions.

1) 3"x2" or 4"x2"? The net seems to suggest 3”x2” will be fine.

I am planning to use 3"x2" with 40cm centres and 12.5mm plasterboard each side. Anyone got any comments? Wall is 4m long and 2.7m high.

2) The floor joists span 5m with approx 45cm centres with three 8"x2" joists and then two 8"x3" joists (to account for the slab in situ for the old fireplace) then back to 8"x2"s. The stud wall will go about 1.5m in at the opposite direction of the joists.

BC has been round and said no need to put extra joists in the span of 5m to account for the extra weight of the new stud wall. However there used to be a shorter (about 2m) stud wall in exactly the same place and I noticed the joists have sagged about 1.5cms over the span of 5m where the old stud wall used to be.

Could this be just age or the old stud wall. Do you think I should double up a few of the joists in any event?

Thanks

 

[Richard C]

I only ever use 4 x 2 studwork; looks & sounds more like a proper wall. IMO, 3 x 2 will be far too flimsy on a wall that size & will shout “cheap & nasty”. Cost difference is minimal.

Don’t forget the intermediate noggins, your going to need 2 over 2.7m height; plan your boarding & fix them accordingly. Fit additional noggins for power points, light switches & anything else you want to hang on the wall. What is the wall being used to partition? Some walls must have sound insulation but it’s a good idea to put it in anyway.

The span & weight it’s been supporting probably accounts for the 15mm sag; old stud wall would have some bearing but not much. They are stout joists but 5m is a bigish unsupported span, has an intermediate support wall been removed from below at some point? Although BC don't require it, sistering some of the joists wouldn’t be a bad idea; I’d also jack ther existing joists (but don't overdo it) to level up the floor a bit after sistering.

Why is BC involved?

 

[Magrah]

Hi Richard

Thanks for the advice.

Good point I was going to use three noggins but sounds like two will do.

Basically one bedroom was 5m x 5m the one next to it 2.5m x 4m, they were separated by a wall and chimney. I have removed the wall and chimney to make two rooms 3.75m x 5m x 2 hence the BC involvement.

Yes the span is wide even for that size of joists! No wall has been removed underneath, they span from the outside wall to a centre load bearing wall (not spine). I’m tending towards sistering as well though spoken to a few people and they said don’t bother but its no good wishing you had done it later. Do you think every alternate joist is in order or too much / to little?

 

[Richard C]

Try sistering, the joists in the centre of the (unpartitioned) room first, thats where they will have the greatest effect once the floorboards are down; see how it feels & go from there. Problem is you probably won't be able to jack the joists unless you do them all; stagger the timber connectors & bolts.