Sound proof stud walls

[Cocoa]

Hello all!

I am looking for some advice on the best way to sound proof a stud wall! Last year, I took down the partition walls on my top floor. Local sources (all completely unverified) think that my little row were probably weavers' cottages, with the ground and first floor for the family, and the second floor an open workroom. The partition walls certainly seemed to have been added at a later date - judging from the newspaper with which they were amply papered, I would say sometime around 1890. Basically, the walls were a row of tongue-and-groove floorboards nailed to a frame, anbd papered over. At a later date, someone felt that faux-wood panelling (using mdf boards and a dark wood trim) would be an improvement on the existing arrangement. Either way, basic sound proofing does not appear to have been aconcern back then!

Anyway, I took it all down to reconfigure the floor to make room for a shower. In its place my builders put up a proper stud wall which we had filled with thermafleece. Not being quite so adept with lime plaster as I am now, I let the builders put plasterboard up, and skim over. It looks nice, but a quiet conversation in one bedroom can be heard in the neighbouring room. Not ideal!

So, here are the options as I see them:

1.) Take down the plasterboard, and replace with reed matt and lime plaster
2.).... or hemp plaster. I have read that it has higher insulation properties than haired lime plaster.
3.).. or even ecocork. What puts me off this option is that it requires an additional coat of consolidation mortar, which needs to be harled. It's not a technique I have any experience at, I don't know if it would work with reed matt, and I am so c,ose to finishing all my plastering I am a reluctant to try and inexpertly apply a new technique (my first attempts at plastering were so time consuming and inexpert, I have redone all my initial efforts!)
4.) Get a flatpack wardrobe from Ikea for that entire wall, and fill it with lots and lots of clothes!

Could anyone advise?

Also, is there some natural insulation inside the stud wall that would be significantly better than thermafleece? I have also considered taking up a few floor boards and shoving some thermafleece underneath the wall, maybe a foot or two on either side. Would that be necessary, as I plan to carpet (carpet + thick acousting underlay)?

 

[Penners]

To be frank, I don't think any of your numbered solutions is going to make a significant difference to the sound insulation properties of the wall, other than number 4.

Effective sound insulation requires a number of factors:_

* Mass. The more massive the barrier between the sound source and your ear, the better.

* Prevention of air movement. Sound (forgive the blindingly obvious statement) travels through air. So in order to try and prevent its transmission, you need to try and eliminate any and all routes for air to travel or transmit sound waves between the two rooms. Remember that this includes underneath the floor and above the ceiling.

* Layers. The more "leafs" of massive surface that the sound encounters, the more it will attenuated - particularly if those leafs are as unlikely as possible to resonate (ie: to vibrate due to sound).

My approach to your problem would probably be to try and create a wall that consists of a very solid lattice studwork frame, with no more than about 400mm between studs or noggins, to which is applied 2 or more leafs of 12.5mm sound-block plasterboard, on top of an acoustic insulation mat. None of the layers is nailed or screwed into place - they're all glued. Then finish with a plaster skim.

http://www.british-gypsum.com/products/gyproc-soundbloc

But remember that your ceiling and floor are both resonant surfaces, too, probably with air access above and below to the next-door resonant surfaces. So you need to address these problems, too.

This is a very useful website:-

http://www.soundstop.co.uk/soundproofing_walls.php

Sound insulation can often be a difficult and expensive process, so I urge you to read up as much as possible on the subject, before you start spending money on your chosen solution.

 

[Keith Bowman]

When we had a soundproof recording studio built in our offices many years ago I think there were three layers of plasterboard, with the joins running in opposite directions, on each side of the studwork. Try googling 'soundproofing for a recording studio' - might give you some ideas, and you don't need to go so far that it is absolutely dead silent

 

[Penners]

you don't need to go so far that it is absolutely dead silent

I suppose that depends on what you get up to in the shower room!

 

[Cocoa]

Thank you for the replies!

My approach to your problem would probably be to try and create a wall that consists of a very solid lattice studwork frame, with no more than about 400mm between studs or noggins, to which is applied 2 or more leafs of 12.5mm sound-block plasterboard, on top of an acoustic insulation mat. None of the layers is nailed or screwed into place - they're all glued. Then finish with a plaster skim.

Fortunately, I already have the studwork frame in place, it's just that the current level of insulation is insufficient to provide a reasonable level of privacy! you're right, I don't need the place to be as airtight as a recording studio, by any means. I had expected the thermafleece to deaden sound more than it does, so I am a bit disappointed there.

But remember that your ceiling and floor are both resonant surfaces, too, probably with air access above and below to the next-door resonant surfaces. So you need to address these problems, too.

I had thought of that! The floor above is the attic, which has 270mm (or whatever the required amount of loft insulation is) above it. I've no idea whether that is sufficient, but it is all boarded over now to provide storage space. It is being used as storage as well, with absolutely loads of stuff up there, and I shrink at the thought of moving it all to check whether the roof is the problem! I hadn't done anything with the floor, though, so I may try lifting floorboards and insulation 1-2 feet on either side of the wall, before I start demolishing the work I paid sometime to put up only 12 months ago. The offending wall is between 2 bedrooms, rather than a bedroom and a bathroom...

Soundstop.co.uk is very useful, and is of the opinion - along with a a number of other sites - that the best solution is to remove the plasterboard on one side, and replace insulation with something more specifically targeted at acoustic insulation. There are quite a few options - both soundproofing boards and acoustic rock wool, and several sites do mention the acoustic plasterboard as well. My thought is that, if I lathe and plaster instead of putting drywall up again, (i) the plaster key is the kind of uneven surface which limits noise transfer (along the lines of the 'dot and dab' method), a few coats of lime plaster would be thicker than plasterboard (back to your point on mass, Penners) and of course, I could do it myself, whereas anything involving gypsum I would have to someone in and pay them!

 

[malcolm]

Penners has it spot on - it's primarily mass and sealing that you need. That's not to say absorption isn't good too, but it won't do the job by itself - it just deadens the higher frequencies. The angles created by lath and plaster won't help a lot. That would be like the egg box shape in anechoic chambers, but anechoic chambers also tend to have 18 inches of insulation stuffed into the egg boxes and a good thick concrete wall outside to keep the noise out.

The internal walls in modern houses are too light weight. The most space efficient way to reduce noise transmissiblity is to use a rubber sheet called heavy layer behind the plasterboard (or behind the new lathe and plaster). Go for at least 10kg/m2. Properly installed that can give you a 20dB reduction by itself. The heavy layer needs to be taped at the edges and works best when it does not contact the surface of the plaster finish, or is separated from any finish by a skim of soft foam.

Flanking paths for noise might be found in the ceiling, floors, or anywhere else where the builders have left gaps. Those need covering too, and a return into the room might help.

Any further sound absorbing material in the wall is best dense and thick acoustic stuff. Thermal insulation is not tightly packed enough to have much effect on noise.

 

[lukekelly]

We used staggered studs between our room and the nursery with wood wool board / hemp plaster finish and "acoustic" rockwool, which has been highly effective. (Two sets of offset studs so there's no direct connection between the two rooms, except for at the sole and top plates.) If you have the space to lose I'd do the same - you'd need to widen the plates with some 2x2 - or even construct a second stud frame, before finishing with a well taped double layer of plasterboard.

 

[Penners]

Two sets of offset studs so there's no direct connection between the two rooms, except for at the sole and top plates.

Good plan, Luke. This will greatly reduce the risk of resonance.

 

[Cocoa]

thank you so much for the advice, and apologies for my own late reply. It is hard to get my head around the idea of dismantling work that was done so recently, and creating yet more dust and mess in one of the few areas where dust and mess wasn't QUITE so prevalent! :shock: Anyway, I have now accepted that it is a necessary evil, and am much calmer!

So it sounds like I need to do the following:

- remove plasterboard from one side of the new stud wall (leaving the other side intact - no point in creating even more work than necessary!)
- replace thermafleece with acoustic rockwool
- insulate underfloorboard, also with rockwool (I am planning an 'insulation barrier' of a foot or two on either side of the finished stud wall. I confess that is completely arbitrary, but I don't think it feasible or necessary to insulate under the entire floor!) I am wondering whether the floorboards would make this a bit useless, however: as it used to be just one big workroom, the floorboards run under the current stud wall. From what you are saying, sounds could travel along these, although it would be mitigated by the underlay & carpet I will eventually get down. Or perhaps I could try these?
http://www.cellecta.co.uk/cellecta-brands/yelofon-acoustic-floor-insulation-products/yelofon-es-fs-acoustic-flanking-strips/
- tape rubber acoustic mat to the existing stud
- construct new staggered stud wall, which doesn't touch the rubber mat...
- reed matt & plaster, and paint....
Isthat about right, or is that overkill?

And I'll have to remove all the electrical sockets, which were positioned on the stud wall instead of the old stone wall! Grr. :roll:
-
I do think the builders should have anticipated that there would be issues with sound between the rooms!

Thank you again for the thoughtful, detailed replies...

 

[Penners]

Your common floorboards are a concern. There's no doubt that they will act as sound conductors between the rooms, to some degree. If it were me, I think I would (if it's practicable) put a sawcut through the boards along the line of the stud-wall sole plates, in order to create a few mm of air-gap. As you are planning a double stud-wall structure, you can then lay one sole plate on each side of the sawcut, with a strip of acoustic mat under each sole plate to keep them clear of contact with the floor. When the carpet is laid, I would put acoustic underlay underneath it. Something like this (others are available): http://www.domesticsoundproofing.co.uk/soundproofing/acoustic_carpet_underlay.htm

I don't think you need to use flanking strips, so long as you tape the edges of the carpet underlay to the bottom edges of the vertical acoustic mat (which I still recommend - see below), to make them completely contiguous.

Your plan for the wall surface wouldn't be my choice, given the need for acoustic insulation. I don't see thermafleece, acoustic rockwool, reed mat and plaster as sufficiently massive or resistant to resonance. Please see my post above on the subject of acoustic insulation mat under two layers of acoustic plasterboard, plus plaster. Of course, it would also be beneficial to stuff the "cells" of each studwork wall with thermafleece or rockwool, but try to leave an air gap between the two.

I'm probably sounding (!) rather authoritarian about this, but of course it's up to you how far you want to take this sound insulation project. I'm simply telling you what I (an amateur in these matters) would do for the best possible result as I see it.

PS: What is the situation/construction above the ceiling? Sound could pass over the wall as well as underneath.

 

[masochists-r-us]

We've used acoustic plasterboard back filled with acoustic insulation slab from Wickes. Very effective and keenly priced too.

 

[masochists-r-us]

We went for acoustic plasterboard back filled with acoustic insulation slabs from Wickes. Well priced and very effective.By the way, I don't work for Wickes or anyone for that matter.