50mm insulation ok for a 80mm bathroom stud wall? (rock wool slabs)

[Joe Fixit]

Hi,

I've seen online people recommending tightly packing in insulation and others saying leaving a little gap especially on the shower/wet walls.

Stud walls only 80mm so have bought 50mm but now wondering whether I should have got 100mm and either jam or in or trim it

 

[endecotp]

50mm of rockwool isn’t very much insulation.

What sort of wall is this?

 

[Joe Fixit]

50mm of rockwool isn’t very much insulation.

What sort of wall is this?

Its a partition stud wall. Bedroom one side, bathroom the other. The depth of the stud is actually about 70mm hence why I originally bought 50mm insulation pads. But now decided to add 18mm battens on the face of the studs to build it out deeper so I can fit a niche.

It's plasterboard facing bedroom and will be putting hardieback bathroom side, tanking and porcelain tiles

 

[endecotp]

An internal wall… are you insulating for noise? You wouldn’t normally thermally insulate an internal wall unless one side or the other was unusually cold. Is it an unused spare bedroom?

Are you using acoustic rockwool?

I don’t think there is any reason for a gap in this scenario but others may have opinions. The wall should be impermeable i.e. tiles or shower panels etc. so no moisture should be inside the partition.

 

[Joe Fixit]

An internal wall… are you insulating for noise? You wouldn’t normally thermally insulate an internal wall unless one side or the other was unusually cold. Is it an unused spare bedroom?

Are you using acoustic rockwool?

I don’t think there is any reason for a gap in this scenario but others may have opinions. The wall should be impermeable i.e. tiles or shower panels etc. so no moisture should be inside the partition.

Yes, got soundproofing insulation (attached photo on reply above).

And yes, hopefully it won't have water or moisture inside the partition once all the wall goes up. The only chance is that the side of the partition faces an external wall with potential air slipping in from the side?

 

[endecotp]

OK.

Regular 100mm rockwool could probably be jammed into 80mm, but the acoustic is more solid. I think you should go with what you have.

 

[Joe Fixit]

OK.

Regular 100mm rockwool could probably be jammed into 80mm, but the acoustic is more solid. I think you should go with what you have.

Do you know if I need a vapour barrier?

 

[endecotp]

Do you know if I need a vapour barrier?

No, I wouldn’t have thought so. As above, the bathroom wall would normally be tiled or otherwise impermeable. I don’t think I’ve ever found any sort of vapour barrier in an internal stud wall.

 

[phatboy]

50mm in an 80mm wall is fine.... I cannot prove it but I think the wall I partially filled performs better than the one I full filled. There is a theory that the sound is killed off better when it has air space and has to pass materials of varying density, all gets too complex for me though!

 

[Joe Fixit]

50mm in an 80mm wall is fine.... I cannot prove it but I think the wall I partially filled performs better than the one I full filled. There is a theory that the sound is killed off better when it has air space and has to pass materials of varying density, all gets too complex for me though!

Yes, that's why I mentioned there seems to be 2 schools of thought on this. Was hoping this forum could decide for me

 

[noseall]

50mm in an 80mm wall is fine.... I cannot prove it but I think the wall I partially filled performs better than the one I full filled. There is a theory that the sound is killed off better when it has air space and has to pass materials of varying density, all gets too complex for me though!

Air is a good thermal insulator but a lousy sound insulator. Occupying at least some of that void with insulation, serves to muffle (absorb) noise, especially those of the higher frequency. However, there is no substitute for dense materials, when it comes to sound proofing.

 

[^woody^]

50 rockwool is fine for sound in a partition.

The quality of the fitting and boarding are important

 

[Joe Fixit]

50 rockwool is fine for sound in a partition.

The quality of the fitting and boarding are important

Thanks. It's plastered on the bedroom side which I won't be touching. I've made the new wall frame pretty flush now so Hardiebacker can hopefully be very flush to the face. Then will be tanking and porcelain tiled.