Should condensation/moisture be a concern?

[Michaelsf90]

The party wall on my house is solid brick. No cavity. Two brick width thick so nine inch. I'm building a stud frame between ten mm and an inch away from the party wall in an attempt to soundproof. The gaps in the stud will be filled with rockwool. One side of the stud will be fixed to an exterior wall but the exterior wall is cavity. My question is will I need a vapour barrier anywhere in this stud? I'm thinking more of moisture/warm air getting through and the gap between the wall and the stud being cooler. By rights the gap should be air tight. The plasterboard will be sealed for soundproofing purposes so by rights it should be air tight but I'm guessing moisture could still get through seeing as all materials breathe? Very much a novice with all this and the last thing I want is to cause mould and damp problems but I also want a soundproof wall to work which means being air tight

 

[Mr Chibs]

Why not just bond foam insulation direct to the wall and add a double layer of plasterboard, or for an easier job, insulated plasterboard, bonded straight to your walls with adhesive... no need to make a frame.

Wouldn't think you'd need vapour barrier, as the other side is also an internal wall. The temperature will be similar on 'their' side.

 

[Deleted member 174758]

You may want to consider a few mods to the standard stud wall. First off, I'd recommend putting a layer of the old-style carpet under-felting between the floor/wall/ceiling and your studding - that way you get less vibration transferred into the stud work from the hard surfaces abutting it. Secondly stop your plasterboard a few millimetres short of the walls/ceiling/floor and caulk the gap with an acoustic sealant (or at the very least a paintable silicone). Lastly try, if possible, to double skin the wall with all the joints staggered - I'd also recommend scrimming the joints on the first layer and sealing with plaster or jointing compound before applying the second layer. I did this on our last house and it was really effective

 

[JP_]

Why not just bond foam insulation direct to the wall .

I think that would be more expensive and less effective for sound insulation?

 

[foxhole]

Needs a bigger gap to have any chance of soundproofing and correct type of board .

 

[Michaelsf90]

Everywhere seems to say use kingspan or celotex which has no acoustic properties whatsoever. Next door is rented and it isn't often they are in. Believe me we know when they are and even in -4 temperatures they seem to have windows open so it will be a lot cooler on their side than on ours. I don't know if this will cause a problem?

 

[Michaelsf90]

You may want to consider a few mods to the standard stud wall. First off, I'd recommend putting a layer of the old-style carpet under-felting between the floor/wall/ceiling and your studding - that way you get less vibration transferred into the stud work from the hard surfaces abutting it. Secondly stop your plasterboard a few millimetres short of the walls/ceiling/floor and caulk the gap with an acoustic sealant (or at the very least a paintable silicone). Lastly try, if possible, to double skin the wall with all the joints staggered - I'd also recommend scrimming the joints on the first layer and sealing with plaster or jointing compound before applying the second layer. I did this on our last house and it was really effective

You know what your taking about job and knock. I've got some sound isolation tape to put on the studs where they are being fixed to the wall, floor and ceiling. I've got acoustic sealant for the edges. What is scrimming? My plan was to treat the first layer like the last. Seal the edges and joints with acoustic sealant before applying the second layer. With it being so air tight do you think moisture will be a problem?

 

[Deleted member 174758]

What is scrimming?

Plasterer's self-adhesive scrim tape:

Laid across the joints before filling them with plaster or jointing compound - gives the plaster/filler something to adhere to. Alternatively you could just caulk the joints on the first layer with silicone or acoustic filler. The main thing is to seal any gaps

Everywhere seems to say use kingspan or celotex which has no acoustic properties whatsoever.

On apartment block new builds they tend to use Soundbloc boarding over the insulation where noise transmission is considered an issue - this is 15mm thick and is quite a bit more effective than 12mm grey board. were I redoing my house I'd go with that instead of grey board - but I'd still double board. Problem is that the mauve boards (Soundbloc) isn't often stocked by the smaller builders merchants. I also agree with you that it needs something denser behind it such as mineral wool batting to get the best performance. Mineral wool being denser is a more effective sound-proofing material than Cellotex/Kingspan or fibre glass (I did experiment with this years ago to prove to myself the difference) and I think that the haphazard arrangement of fibres in mineral wool also helps disperse noise as it travels through the material. Having a small air gap (just enough to prevent transmission from the wall directly into the mineral wool) is a good idea, but I personally don't think it needs to be more than about 25mm. The things you have to watch are getting the fit of the mineral wool to be as tight as possible between the joists (for which it is maybe worth buying one of those Stubai insulation knives off Amazon - they make cutting many types of insulation cleanly and accurately a doddle) and making sure that elsewhere you minimise the contact between the hard parts of your wall and the surrounding building (which I dealt with by using felt and silicone as detailed above)

 

[foxhole]

You know what your taking about job and knock. I've got some sound isolation tape to put on the studs where they are being fixed to the wall, floor and ceiling. I've got acoustic sealant for the edges. What is scrimming? My plan was to treat the first layer like the last. Seal the edges and joints with acoustic sealant before applying the second layer. With it being so air tight do you think moisture will be a problem?

No moisture can enter with no air movement .

 

[Michaelsf90]

With the brick being solid with no cavity between us and next door could moisture not come through there? I think I'm possibly overthinking

 

[Michaelsf90]

Thank you job and knock. Do you think the isolation tape will do the same job as the felt? I'm going to use 15mm soundbloc and then 12.5 as I've heard different densities are better

 

[Deleted member 174758]

Do you think the isolation tape will do the same job as the felt?

I honestly don't know having not used it in this way. What you are trying to achieve is a good seal between the wall and the frame which is flexible enough not to allow sound vibration to be transmitted through/across it. If the tape achieves that, then go for it

No moisture can enter with no air movement .

If you have gaps that completely negates the effect of installing sound proofing. For a party wall there shouldn't be any issues of moisture, surely?

 

[Michaelsf90]

From the description it says that's what the tape is for. Jcw acoustic isolation tape or something like that. I wouldn't have thought so. I think I'm over thinking the moisture to be honest

 

[foxhole]

I think I'm over thinking the moisture to be honest[/QUOTE]
Yes

 

[cwhaley]

even in -4 temperatures they seem to have windows open

What's wrong with that?