PIR in stud wall without gaps

[tramandy]

I know I sound daft, but why can't I find 75mm Studs which are actually 75mm to match the 75mm thick PIR? Same with 100mm. I don't want gaps for services as it will be a workshop where trunking isn't an issue. Do I just need to go somewhere other than Wickes/TP etc?

 

[phatboy]

If you go to a timber yard who don't plane all the wood, you should get the size you want.

The sizes on planed wood are given pre-planing.

 

[freddiemercurystwin]

Because the building industry is crap.

 

[DAZB]

Common problem and the same with sheet materials as some is 8 X 4 and others are 1220mm x 2440mm. I have resorted to building studwork up with 4 or 6mm ply to make it tally with PIR sheets.

 

[phatboy]

Common problem and the same with sheet materials as some is 8 X 4 and others are 1220mm x 2440mm. I have resorted to building studwork up with 4 or 6mm ply to make it tally with PIR sheets.

8x4 is pretty much 1220 x 2440. It's the metric sized bits that are 1200x2400. Yes, the discrepancy between ply and plasterboard is a pain, in flat roofs for example!

 

[cdbe]

There was a debate somewhere about whether it mattered - the plasterboard would have adequate strength to span the 38mm gap. At the same time, nice regularised timber is far better to work with than old rough sawn.

 

[noseall]

8x4 is pretty much 1220 x 2440. It's the metric sized bits that are 1200x2400. Yes, the discrepancy between ply and plasterboard is a pain, in flat roofs for example!

Door casings haven't caught up with regularised timber, in that the timber is thin, casing is wide - meaning shoite loads of skim both sides.

 

[DAZB]

8x4 is pretty much 1220 x 2440. It's the metric sized bits that are 1200x2400. Yes, the discrepancy between ply and plasterboard is a pain, in flat roofs for example!

Yes, that's the one's... it's been a long week.

 

[^woody^]

Stud walls were traditionally built with roughsawn timber, and these were the actual sizes.

Nowadays timber is generally regularised or CLS, which is smaller.

If you can't find rough sawn, get some hardboard or suchlike and cut some strips to line the studs.

If you are boarding on both sides of the frame, you could keep the room side flush, and have the gap on the external side and just board across and it will be OK.

However it's always best to line the inner face of a frame wall with insulation to avoid cold bridging of the timber studs.

 

[tramandy]

Stud walls were traditionally built with roughsawn timber, and these were the actual sizes.

Nowadays timber is generally regularised or CLS, which is smaller.

If you can't find rough sawn, get some hardboard or suchlike and cut some strips to line the studs.

If you are boarding on both sides of the frame, you could keep the room side flush, and have the gap on the external side and just board across and it will be OK.

However it's always best to line the inner face of a frame wall with insulation to avoid cold bridging of the timber studs.

Thanks woody, I was going to use insulated plasterboard to avoid the cold bridge, or one wall will have 25mm PIR with ply over for supporting stuff on the wall better. I can use a vapour control sheet between ply and PIR, but the insulated board will be the VC, and so any gap behind wouldn't be fully on the warm side.

 

[If in doubt...]

8x4 is pretty much 1220 x 2440. It's the metric sized bits that are 1200x2400. Yes, the discrepancy between ply and plasterboard is a pain, in flat roofs for example!

I found out about this when erecting a flat roofed pergola in the garden. Took care in spacing the roof cross struts / joists nicely and then wondered why the OSB roof had overhangs . Now I know