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What material for party wall sound insulation?

mrdiplomacy

Standard Member
Hello, hoping someone here can help me. I'm at the beginning of renovating the living room and the party wall badly needs treatment to reduce sound from / to the neighbours.

Fortunately, there's a relatively small amount of wall to treat - 2 alcoves either side of the fireplace.

I intend to fix a stud partition hard up against the back of each alcove and fill the ~2" air space with appropriate material. To finish probably some 9mm oak veneer MDF.

I have the chance to get some rigid foam insulation board of the right thickness for no money, but would this be noticeably worse than say, conventional fibreglass wool, or even proper acoustic mineral wool? What should I be using for not too much money, say ~$50? Any idea where I might find such material... in Lincoln? :)

Is there any chance I will actually make things worse doing what I plan to do?

Any comments much appreciated.
 

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clockworks

Novice Member
Your best option would be to build a proper cavity wall, using blocks, and fill the cavity with insulation. A block wall is far better at cutting down on low frequency sound.
I think that the fireplace might be a problem - I assume that it leads to a shared stack with the next door property? If it does, you'll probably find that wall at the back of the fireplace isn't very thick. The flue will also allow sound through to the upstairs rooms.
 

mrdiplomacy

Standard Member
clockworks, thanks for the advice.

I agree, that would be the best solution,

but I'd lose a lot more room space. The alcove is about 450mm deep, leaving just about enough room for shelving and AV components behind the line of the chimney breast. It's the same on the neighbours side, so lots of brickwork between us there.

I think the wall thickness will be uniform across that back wall - why would the fireplace wall be more of a problem than the alcoves?

I'd not considered the fireplace, but since it's being replaced - shame to lose that beautiful '70s brickwork ;-) - perhaps I can do something about that back wall. I'm sure I can instruct the builder to add a 2nd layer of blockwork at that wall, if the flue position allows it. Otherwise, something similar to the alcoves...

If I do it with studwork, I'm in danger of improving some frequencies ( voices and TV noise is what I can occasionally hear) with the insulation used - hence the question - and making some worse due to the potential resonance of the studwork structure itself... :rolleyes:
 

clockworks

Novice Member
mrdiplomacy said:
I think the wall thickness will be uniform across that back wall - why would the fireplace wall be more of a problem than the alcoves?

I'd not considered the fireplace, but since it's being replaced - shame to lose that beautiful '70s brickwork ;-) - perhaps I can do something about that back wall. I'm sure I can instruct the builder to add a 2nd layer of blockwork at that wall, if the flue position allows it. Otherwise, something similar to the alcoves...
The fireplace would be more of a problem because of the difficulty of soundproofing it. The alcoves are easy to get to, the inside of a chimney breast isn't.
Does the fireplace just have a tubular flue, or is it the traditional brick flue, which goes all the way up to the stack in the loft? Is there a fireplace in the room above?
If it's a brick flue, you really need to soundproof it all the way up to ceiling level, preferably all the way to the loft, not just behind the fireplace.

Have a read through the older threads on here - many people have said that the main problem is sound leakage. Treating 99% of a wall is not enough, you need to do 100%.
 

mrdiplomacy

Standard Member
OK, understand now. Just to be clear, an open cavity fireplace with an open brick flue, left untreated would be a major problem, then? - clear leakage path all the way up to the ceiling in an area I can't reach.

I'll find out what the existing flue is tomorrow when the old fire and brickwork gets skipped. There's no fireplace in the room above but there is a ventilation plate... the house was built in the '40s if that's any help.

Ultimately, there'll be an open cavity within the chimney breast for a gas stove. A new flue liner - 4" tubular steel? - will be fitted, anyway, to serve the new appliace, is that relevant?

Given the above, some treatment at the back of the cavity would be a good idea?

Also, I take your point re sound leakage, this means properly sealed gaps all around, which in itself involves a bit of a rethink regarding how I route cables...

Thanks again for your time :D
 

Flimber

Distinguished Member
Jeebus, this thread is built for me. Was going to start my own with an identical problem.

Basically, the neighbour's TV is driving me nuts. It's either an indistinct bassy mumble of voices or else can be so loud that I can use their volume for my pictures :thumbsdow A couple live next door (late fifties), his hearing isn't what it was ("eh ?" "pardon ?" "you what ?") and, get this, he doesn't think their TV is too loud, even though it can be heard in the street through their double glazing. So, as he doesn't think there is a problem, I guess we're all imagining it :rolleyes:

So, I'm now considering some sort of insulated stud wall in each alcove next to the chimney breast. What I want to do - ideally - is build shelves in each (semi-planned anyway). Left side is 106x36cm; right side is 112x36cm. I'm leaning towards a U-shaped design to 'seal' each alcove completely. Perhaps soundbloc plasterboard with rockwool within the void (but not touching the back wall) screwed tight, green-glued and plastered over. Where the stud 'sides' end I want them plastered flush with the front of the chimney breast. Perhaps with a lip to hide the extreme edges of the shelving (hope that all makes sense). Possibly even airtight doors over everything after that...

Another problem is that this room has a wooden floor and the cellar beneath is like an echo chamber for next door's telly. I can see a few air gaps down there but some wooden bits abutt into our brickwork, which is mortared to theirs and transmitting all their bad vibes into our space. So I need to fill these gaps but I'm also considering extending the studwork above right down into the cellar a by couple of feet (close to the lecky fusebox).

A further measure is to take up the wall-most floorboard(s), shave a cm off the edge and replace so they 'aint touching the wall at all. I'll have to do this anyway if I want to extend the false wall into the cellar.

Mike.

Oh, and welcome to the Forums, Mr. D. :D
 

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clockworks

Novice Member
That ventilator in the upstairs room is probably all that remains of the original fireplace. When fireplaces are removed and blocked in, ventilators are installed to reduce the risk of dampness from the "stale" air.
You've probably got four brick flues running up to one stack - two for you, and two for the neighbour. There will most likely be four chimney pots on top of the stack, unless they have been removed and the stack capped.

When you get your new stove and liner fitted, it might be a good idea to get the installers to fit a full-height liner and completely back-fill the existing brick flues, rather than just fitting a plate over the hole at the bottom, and passing a short liner into the brick flue.
Building a new block wall at the back of the fireplace as well should solve any sound problems.
 

mrdiplomacy

Standard Member
clockworks - I think I'll have to see the brick flue to understand what's going on a bit better. Presumably, it's a much bigger cavity which then allows the passage and fitting of a 4" flue liner?

When you say 'backfill', what kind of material would you suggest and how would it usually be done? I can't see how it would be possible to fill the whole of the flue cavity, aside from dumping a load of sand in from the top of the chimney!!!

A full height liner will indeed be fitted, the installer was insistent that anything else would leave the gas stove at risk of getting clogged with falling debris.

As for the blockwork, it depends if there's room, the stove has to sit under the flue liner and it won't necessarily allow a lot of flexibility - will soon see.

Flimber - we're thinking along similar lines, although you seem to be doing a much more sophisticated job of it by the sound of things. Have read a bundle of posts on here each espousing the use of this magic green-glue - what the hell is it, what's it for, how do I use it, where do I find it, do I need it...???! :) Soundblock plasterboard, what's that??? Presumably, I find all this wonderful acoustic hardware at my local friendly sound insulation dealer... sadly I know of no such beast in this part of the world (Lincoln). Do I need to get supplies like this mail order / online?

1 question from your post - why do you leave the rockwool isolated from the back wall? Surely the material itself is a better sound insulator than an air gap?

For my own alcoves, I'll line as described with a stud wall at the back only and use bookshelf strips and < thick > shelving to prevent bending from heavy AV kit :)

Thanks again guys for all the help. :clap:
 

clockworks

Novice Member
The brick flue is probably the full width and depth of the chimney breast, less the size of one brick in depth and two bricks in width (4 1/2" and 9" approximately). It needed to be big, as it was probably designed for an open fire/grate.
Towards the ceiling it will taper, so that it runs to one side of the upstairs fireplace. The bedroom fireplace would normally be a small cast iron insert, with a narrower flue.
The stove installer should know what to use - something like vermiculite, an asbestos substitute. This could probably be "blown in" from the fireplace.

You could build a block wall using narrow blocks (or bricks) and a small airgap, meaning you would only lose 6 or 7 inches of depth. You can get flexible liners, if necessary.
 

roofman

Standard Member
you would normally get a roofer to backfill wih vermaculite. When building the stud wall I would build a frame of 2 x 2 timber, fix it to the floor and ceiling - NOT the party wall. Put some proper accoustic insulation in this and then fix resilient bars screwed to the stud wall. Thn fix 2 layers of plaster boards - not lining up the joints and screwing into the resilient bars NOT the timber. You will get all materials from your local Jewsons. The most important bit is the resilient bars, you wont hear a thing through these walls.
Cheers
Stuart
 

mattym

Banned
mrdiplomacy said:
the chimney!!!


Have read a bundle of posts on here each espousing the use of this magic green-glue - what the hell is it, what's it for, how do I use it, where do I find it, do I need it...???! :)
Green Glue is a visco-elastic damping material that you apply between layers of plasterboard(or soundblock etc) to stop the structure resonating. Outperforms resilient channel, or used with RC improves the performance of the assembly.:smashin:
 

mrdiplomacy

Standard Member
mattym - Sounds like good stuff - is there any preference for the sheet materials you suggest - plasterboard / soundblock - over wood? I'll be using veneered mdf, presumably, I could bond that to some backing material like plywood or plasterboard etc?

roofman / clockworks - thanks again. Vermiculite it is then! :) The carpet is up upstairs and there's a bundle of old quarry tiles to bear witness to the old fireplace. The chimney breast is built with quite an impressive angle in the roofspace.

Was reading up on stud walls and will follow your advice. Problem is the floor joists above run in the same direction as the studwork and the nearest beam is about 6" from the back wall, I'd lose a lot of space - Is there any way to fix the header plate closer to the back wall?

Thanks.
 

mattym

Banned
green glue works by being squashed between 2 layers, best thing to do is check out the audio alloy website for installation instructions. Ted and Brian from AA pop in now and then, they may look in and give a little advice too
 

mattym

Banned
as regards fixing the wall to the ceiling, ideally you want a firm fixing

#1 Use construction adhesive and mechanical fasteners to attach the top plate to the existing drywall. No connection to the joists.

#2 Cut into the existing ceiling and insert a noggin between joists and fix your plate to this new beam
 

Chrannbow

Standard Member
I know that this thread is 3 years old but I was wondering if either Mrdiplomacy or Flimber are still out there and whether they went ahead their renovations. If so was the sound insulation successful. I have exactly the same setup with a chimney and two alcoves in a 1940's terrace and am considering additional sound insulation. The problem is not severe and I can only here raised voices and outbursts of laughter.
Any lessons learnt or advice on whether sound insulating the alcoves and maybe blocking off / insulating the chimney really works.
 

mrdiplomacy

Standard Member
Hi Chrannbow,

A good time to review. Overall, I would say I made a modest effort at sound insulation and got not much if any improvement. To be clear on what was and wasn't done, read on.

Pre-existing arrangment was as yours, but the fireplace cavity was filled with debris / sealed up and fronted by a lovely 70's gas fire and faux stone brickwork spanning the whole room to about 18" height - nice! Note - the fireplace cavity was filled up.

All that debris and brickwork was removed.

- Studwork was firmly fixed to floor, ceiling joists and sidewalls - i.e. no direct connection to back walls.
- Acoustic fibreglass insulation was packed in between the studwork. I didn't put more than 1 layer in and I didn't put any behind the studs between them and the back wall.
- Conventional 9mm plasterboard on top, skimmed over as std, with small gap at the concrete floor.
- 9mm MDF bonded direct to plaster skim using Evostik shock absorbent adhesive - 6 tubes for the 2 alcoves I think
- Flue was left unfilled, had it's new 4" steel liner fitted and the gas fired wood burner style fire fits in quite tight up against the back wall. There's also a plate fitted around the flue to close off the fireplace cavity, it's a board of some kind.

So, how does it perform? Well, not that great. I still get occasional conversations and TV coming through. What's worse is that it's not easy to determine why. I've (hopefully!) improved the alcoves insulation, at the same time as completely opening up the fireplace cavity. I did the best I could with the alcoves, while retaining the minimum amount of space I was comfortable with which seriously restricted my options. I wasn't able to treat the fireplace cavity at all. In truth, it didn't cost me all that much, the job had to be done anyway, the aesthetic result is, in my view, great and I have the good shelf space I wanted. You'd say that sound insulation wasn't my top priority and the results reflect that I think. I've a picture gallery to post, but it's not online at the moment.

What I did right
- studwork was good. It should be as rigid / firm as possible
- 2-layer system of plasterboard/mdf is good - mass counts!
What I think I did wrong
- not enough insulation in / around studwork
- maybe properly seal gaps at stud edges
What I'd do differently
- use thicker / 1 extra plasterboard layer
- backfill chimney cavity w / Vermiculite. I got the advice a little late in the day, so was able to find a supplier. The place I used for the fire claimed to never have heard of the stuff and to be honest they were a bunch of pr#cks. I think this would be worth pursuing, poss use the same people who do cavity wall insulation.

What I didn't do due to constraints
- new blockwork cavity wall would surely be the best option. Much heavier for resisting any sound pressure loading, but would have left me so little shelf depth, maybe 200mm reduction from original?
- thicker studwork. I used only 2" square, only ~1/2" from the back wall. Again more / heavier / more rigid is better. Same reasoning as above, I wanted to retain the space
- Adding material to the back of the fireplace cavity. Simply didn't have the room, assuming I wanted a fire fitting - consider if you can do without / use a decorative fireplace.
- Finally, I didn't give serious consideration to the Resilient Channel option, which was partly due to to time constraints and partly because I didn't understand it well enough. It would also take another inch or so? I'd take the time to have a closer look at this option now.
- I found it difficult to judge the value of green glue. I understand the principle, but opinion did seem polarised at times. My chosen adhesive was slightly less than half the price, not including the solvent gun, which seemed difficult to get hold of, i.e. more ££.

My conclusions from both my research and the job I did was that while good sound insulation can be obtained, it conflicted with all the other stuff I wasn't prepared to compromise on. If you wanted to pursue sound insulation as your main objective, you'd have to commit to it, spend the money and the time doing the job properly.

If I find the time, I'll post up the pics from the build.
Cheers,
Mark.
 

Chrannbow

Standard Member
Thanks for a great review MrDiplomacy, I think you have confirmed my concerns about going ahead with some DIY sound insulation.....even though blocking sound wasn't you primary concern.

I can not currently be sure exactly how the sound is leaking into the room, which makes it pretty difficult to stop it. My latest theory is that it is coming through the shared chimney, rather that through the alcoves. I am wondering if there is less of a barrier between my living room and their living room where the 2 fireplaces / chimneys join - does anyone know if this is likely to be the case in a 1940's terrace? If so I could maybe improve the sound insulation in the chimney and fireplace (how?) - we are not interested in having any kind of fire, so its not needed.

If anyone has carried out any work successfully I would be very interested to know what you did!
 

Ted White

Novice Member
Shared structures conduct vibration exceptionally well. Shared walls, masonry elements like fireplaces and flues, shared exterior walls all conduct.

Since it is often difficult to remove / limit / damp vibration within an existing structure (especially when masssive) the general tenet would be to decouple from the common element altogether. A timbre or steel wall in front of the common element for example. To this decoupled frame you would further consider adding:

Absorption in the form of light (lower density) insulation. High density or "packing" low density simply increases the liklihood that the insulation itself will conduct vibration. It takes surprisingly little insulation to achieve max absorption within a sealed cavity.

Mass in the form of heavy plasterboard. Mass is mass, whether you choose MDF, Plasterboard, Mass-Loaded Vinyl, or cement. More is better, but only to a point.

Damping in the form of one of many damping materials. Often times there are materials being sold as vibration absorbing damping materials that are perhaps not. Any product should have independent lab data.

It must be considered that the perfect wall will not keep sound out. MrDiplomacy has a reasonable wall but it is directly and rigidly connected to the floor, ceiling and side walls. This allows sound vibration a conductive pathway. This is known as flanking noise.

Sealing better would have helped possibly, but not much. More mass would have helped, but not much. Less packing of the insulation would have helped, but not much. A better damping material would have helped but not much.

The problem is flanking I suspect.
 

Chrannbow

Standard Member
I am thinking of going for the option of a stud wall 1 inch away from the existing brick (plastered) wall, with a layer of acoustic quilt(or rockwool) and then resilient bars fixed to the stud wall and a couple of layers of plasterboard sealed to the walls, floor and ceiling. What is the best thing to fix the stud wall to? I have suspended floors (ground floor), that is floor boards with a void underneath. Is it best to take the floor boards up and extend the stud wall all the way down? Is it best to remove part of the ceiling and fix to the joists at the top?

Also, are you also saying there is no way round the problem of flanking other than to treat all walls, the ceiling and the floor?
 

Ted White

Novice Member
Hello,

First, if you can bring that new wall down to the original cement, that would help a great deal with flanking. Second, this new wall would be "decoupled" from the original wall, and therefore would not benefit from the bars. Bars decouple, and the separate wall decouples.

Light dose of insulation, else you risk conduction and reduced low frequency performance.

Then double plasterboard for mass.

You can try this. Then assess the rest of the flanking paths. You'll get improvement, but unknown how much. You would ideally do a similar system on all walls and ceiling.
 

Amioa

Novice Member
*snip*
Mark.
Hi Mark

how much was the evostick stuff you used, and did you seal all the edges of the structures before putting the next layer on? It will be something really simple like that that is your problem.
 

Jon Sheppard

Standard Member
Shared structures conduct vibration exceptionally well. Shared walls, masonry elements like fireplaces and flues, shared exterior walls all conduct.


Dear Mr White,

I have just joined this forum, but am interested in what you said a few years ago about vibration being conducted through insulation.

I am in a 1980s semi and for the first time am feeling much vibration when the neighbour's central heating boiler is on. The one thing that has changed recently is that they have had cavity wall insulation. Do you think these things could be connected?
 

Ted White

Novice Member
Could very well be connected. Blown in insulation is a big risk, and every day that goes by I am more convicted in that opinion. Not a week goes by where there isn't some questionable performance issue associated with an over-zealous installer.
 

peace4me

Standard Member
Hi, i have spent huge amount of time trying to soundproof a party wall, but the more i do the less happy i am with results.

Would like to know of any success with Green glue, added GG to my new soundproofed stud wall on top of 2x layers of rockwool, ressillient bars, MLV and in total 5 layers of acoustic plasterboard and Loads of acoustic sealent.

Yet my partner thinks its made things worse, more TV humming, i know it takes 4 weeks for GG to cure.

Have improved the fire place downstairs compared to the upstairs chimney which is untreated and i could hear the chap next door singing Roy orbison on the other side.

I live in a semi built 1950s and my next step is to take up floorboards upstairs and check for gaps around joists, fill with rockwool.

My partner thinks its futile and the only option is a detatched house.

Any opinions on GG, or tried and tested methods of soundproofing, any success.:hiya:
 

Ted White

Novice Member
p4m, hard to tell based on your description. You may very well have a triple leaf built. In your assembly, have you incorporated more than one air cavity? As you look at the layers created, is there more than 1 layer that is air? Often the use of MLV creates a second air cavity which will significantly limit improvement.

Also all of that insulation + res bars may be pressing on the bars, limiting their movement = seriously reduced isolation.
 

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