1st Floor Inside Walls Build Up

BarneyMc

I checked this the other day with my engineer and he assured me it was NOT structural. There is nothing resting on my 1st floor inside (not perimeter) walls.

Anyway I've attached a photo showing my joists sitting well above an inside wall. This varies throughout the house but ranges from 90mm to 130mm.

Under the joists the membrane will go and under that a 2x2 baton and then the plasterboard. This will not bring the finished ceiling down below the walls.

My air tightness guy said he just needs between 10mm and 15mm to get the membrane over the walls without having to cut and tape down at each inside wall.

So should I just build the walls up to this level and let all work away (this is what my engineer recommended) or is there any advantage of leaving the walls as is, apply membrane, batons and plasterboard and THEN build the walls up to meet the plasterboard (this is what my air tightness guy hinted at)? This would mean not having to cut the plasterboard at each inside wall but might be tricky trying to build the walls up to the plasterboard?

Dudda

I'd build the wall up. If you have the plasterboard continue through it will transfer more sound between the rooms. That's just my thoughts.

sydthebeat

Yep. Sound would be a big issue here.

Finish the air tightness, build up the walls, then slab.

BarneyMc

sydthebeat wrote: »

Yep. Sound would be a big issue here.

Finish the air tightness, build up the walls, then slab.

Or build up the walls (leaving a 15mm gap below joist), apply air tightness, then slab? With the membrane in place would it not be a bit difficult to do the build up under this?

mfceiling

Just be careful that when building up the walls that you don't puncture the membrane.

We were always told never slab the ceilings throughout as one...supposed fire issue? Each room should be individual to each other, as in walls up and then slab the ceilings in.

Might be difficult enough trying to build in 90mm in places (brick?)

BarneyMc

mfceiling wrote: »

Just be careful that when building up the walls that you don't puncture the membrane.

We were always told never slab the ceilings throughout as one...supposed fire issue? Each room should be individual to each other, as in walls up and then slab the ceilings in.

Might be difficult enough trying to build in 90mm in places (brick?)

Just gearing myself up for this this evening! My plan is to build the walls up before the membrane goes on. The airtight guy said he could manage with a 10mm gap but 15mm would be better. In reality this will probably be more like 30mm or more.

Should I be trying to get the gap down to 15mm, or close, to minimise sound travel between the rooms? Under the membrane I'll have a 2x2 baton and then the plasterboard so I suppose that will give me cover of 62mm.

rampantbunny

BarneyMc wrote: »

Just gearing myself up for this this evening! My plan is to build the walls up before the membrane goes on. The airtight guy said he could manage with a 10mm gap but 15mm would be better. In reality this will probably be more like 30mm or more.

Should I be trying to get the gap down to 15mm, or close, to minimise sound travel between the rooms? Under the membrane I'll have a 2x2 baton and then the plasterboard so I suppose that will give me cover of 62mm.

If it is an inch or so, after the membrane has been installed, couldn't you go around and put some dense wool in between top of wall and the membrane.
It's not solid block but will help a bit to stop sound if you're concerned.
It doesn't have to be wedged tight.

BarneyMc

rampantbunny wrote: »

If it is an inch or so, after the membrane has been installed, couldn't you go around and put some dense wool in between top of wall and the membrane.
It's not solid block but will help a bit to stop sound if you're concerned.
It doesn't have to be wedged tight.

Yes, I was thinking of doing that alright. There is one wall that I will try and wedge in a bit of timber to give extra support to the joists. Not needed but will do no harm.