wall cavity treatment

[avdavesound]

Hi everyone, I tried searching but couldn't find anything similar.

A friend just moved into a new house and he likes to listen to his surround sound up loud in the living room and his hi fi upstairs,but the neighbors are banging on the wall I'm looking for some info on the stuff you can inject into cavity's of concrete walls to help keep the noise down. I know its not gonna be 100% soundproof but I'm sure its better than a empty cavity.

 

thanks.

[paulears]

Not as simple as that. While there are all sorts of things that can go into a cavity, the problem you almost certainly have is the ties. The inner and outer skins are bonded together with metal ties, and these are letting inner wall sounds be transferred to the outer - which of course is next doors inner. Rockwool in an airspace works quite well at higher frequencies, but the kind of open cell foam you can squirt in is designed for heat insulation, not sound - most of it is far too light.

 

The things to check first are what the speakers are actually on. If they are attached to the wall - then this is the first thing to change. I'm confused about the suround downstairs and the hi-fi upstairs? Do you mean he has it up so loud that he can hear the loudspeakers in the living room, from the upstairs room? Surely not? If he is doing his, then no doubt his neighbour is right to go mad! The only practical way to add insulation would be to construct a room within the room - plenty of advice on how to do this available elsewhere.

[avdavesound]

the thing is the cavity's are empty no rockwool or anything. speakers are on small stands with neoprene feet. speakers are not the problem. volume is ok not that loud its because theres nothing in the cavity. you can hear conversation next door nearly

 

room within a room is not an option.

 

thanks.

[paulears]

Are you sure it's brick - I assumed it was, but it could be lightweight blockwork. I'm not totally sure, but I didn't think NHBC rules allowed non-filled cavities in new dwellings, especially in a party wall in a semi-or townhouse terrace? If you can hear speaking - then something isn't right. If the sound is getting across the air gap, then before you try anything, talk to the cavity wall people, and explain that it's sound not heat insulation you want - maybe they'll have something special for this. I'd expect a mineral product to work best - but I'd not like to guess on the attenuation - the speech may go away, but I bet bottom end music will still make it through at levels that will still annoy. Sorry - don't know what else to suggest, but it might well be a building fault - as in they forgot the insulation? Are you sure the cavity is empty?

[Steve_Hole]

I have to say, that as somebody who for their day job designs hosuing and flats, if this is a new house / flat - the builders have really &*($£* UP. If it's an older house, they this can be an issue.

 

Filling the cavitty with rockwool might help, but unlikley. The current standard practice for a party wall is a 75mm cavity, unfilled.

 

To overcome the problem, you have two options:

 

1) If new propery, complain - they should have teste the building or built it using robust details - NHBC or Zurich will help you if this was taken out...

 

2) Dry line the wall with something like British Gyspum IWL with SoundBlock board - have a look at there website. Make sure that it is sealed properly to the existing walls.

 

The important thing to remeber is that sound travels in 2 ways - Airbourne and impact. If you are hearing the people next door talking, then it is more than likely there are holes in the party wall... Block these and you should be ok...

 

Steve ;)

[avdavesound]

as in they forgot the insulation? Are you sure the cavity is empty?

yes to both questions. I asked the builder why did he leave insulation or rockwool out and he said there's proper sound proofing going in but in the end it didn't and houses(semi, standard concrete block)are finished. the rest of the walls are insulated just the party wall is not.

[paulears]

I'd suggest Steve's advice, as the housing design specialist - should be followed - the house has a guarantee - make them sort it!

[Mr.Si]

Steve has hit the nail on the head there. As someone who also is involved with Building Acoustics day in day out, I'd suggest something like the British Gyplyner IWL too. Alternatively the Gyplyner Universal.

 

You'd then partially fill the depth of the new void with mineral fibre (15 - 48kg/m3 density) and tack with a couple of layers Soundbloc / dBcheck plasterboard (Staggered joints) would work a treat. when sealing, use a non-hardening mastic (pink grip / grip fill are a couple of these) at EACH layer's perimeter.

If you have sockets on that wall, try and box around the rear of them with plasterboard also. (not that easy though).

 

 

Contrary to popular belief, (esp builders) Mineral Wool / Mineral Fibre / Rockwool / Isowool / whatever you want to call it, is NOT sound insulation. Its purpose is to absorb sound that gets into a cavity or void and stopping it from reverberating around and artificially making the sound louder. If it does this, then the mass layers (which are the insulators) have a harder job to do. So that is what this "insulation" as people call it, actually does.

 

Hope this helps.

 

Si

[paulears]

Moderation: It's been brought to the moderators attention that when posts about d0mestic elecs are posted they get shut down pretty quickly, because we don't do d0mestic stuff - only backstage. This topic is pretty interesting (and I am one of the people posting) - but if we apply the rules equally, then it probably as it deals with sound very clearly at home - it doesn't fit our remit. As we've had some acoustics and building specialists post, we seem to have got to the end and provided enough info for the OP. I'll close it now. If members wish to take the acoustics issues into a new topic that does fit the rules and has a non-d0mestic slant - that would appear to be fine. Thanks. Paul Mods