Sound proof party wall

Gorgie Boy

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Hi All. I've read some great advice on this forum with regards to sound proofing, so wondered if I could get some advice on my own project before buying material.

I have recently moved into a semi detached house and found that the soundproofing on the party wall is pretty bad. We can hear muffled conversations from next door and when I put my ear to the wall, I can make out exact words (not that I am in the habit of doing that of course)! This impacts the ground floor living room and two upstairs bedrooms.

The construction of the existing party wall is dot and dab plasterboard over two layers of brick with a cavity in between the brickwork and presumably dot and dab plasterboard on the neighbour’s side.

We have already done some work in one of the bedrooms (and have made some mistakes). We removed the dot and dab plasterboard and built a 2"x"2 stud frame approximately 15mm away from the brick. We also lifted up the flooring and filled any gaps on the joists and on the brick wall with expanding foam. We then filled the stud frame with acoustic rockwool (trying to maintain an airgap) and then sheeted with one layer of acoustic plasterboard. We then plastered over the top. We did use some expanding foam in a few points on the brick wall behind the stud frame to stop the bounce in the wall. I now know that wasn't a good move. :S

After the work was completed, we later found that we could still hear voices in the upstairs bedroom that I suspect was emanating from the neighbours’ downstairs living room. Sound must bounce up the party wall. I’m hoping that this will be improved when we repeat the soundproofing process in the other bedroom and living room as there will be more holes/gaps in the brick wall that we can cover up.

I now want to make some improvements for the sound proofed walls in the other two rooms. My proposal is:

  • Remove dot and dab plasterboard
  • Fill any holes in brick wall or on joists in the floor with cement (rather than expanding foam)
  • Build a stud frame 15mm away from the brick wall but use 3"x 2" instead of 2"x 2". Also put some rubber strips on the sides of the stud frame that is in contact with the floor, ceiling and side walls.
  • Fill stud frame with a denser and thicker rockwool this time (75mm with 60kg density rather than 50mm with 45kg density).
  • Sheet with acoustic plasterboard
  • Add tecsound 50 over the plasterboard
  • Sheet with another layer of acoustic plasterboard
  • Plaster wall

I've reached out to soundproofing companies and they have all suggested that using a resilient clip system on top of the new stud frame would be worthwhile but that takes the cost of materials to more than I want to pay. Is it really required if we are building a new wall? Does my proposed build sound reasonable? At this stage I just need to block the muffled voices from entering my house.

The wall in the living room is approx. 7.5m by 2.4 and the bedroom walls are 3.6m by 2.3m

I am a complete amateur, so any advice is greatly received.
 
Hi All. I've read some great advice on this forum with regards to sound proofing, so wondered if I could get some advice on my own project before buying material.

I have recently moved into a semi detached house and found that the soundproofing on the party wall is pretty bad. We can hear muffled conversations from next door and when I put my ear to the wall, I can make out exact words (not that I am in the habit of doing that of course)! This impacts the ground floor living room and two upstairs bedrooms.

The construction of the existing party wall is dot and dab plasterboard over two layers of brick with a cavity in between the brickwork and presumably dot and dab plasterboard on the neighbour’s side.

We have already done some work in one of the bedrooms (and have made some mistakes). We removed the dot and dab plasterboard and built a 2"x"2 stud frame approximately 15mm away from the brick. We also lifted up the flooring and filled any gaps on the joists and on the brick wall with expanding foam. We then filled the stud frame with acoustic rockwool (trying to maintain an airgap) and then sheeted with one layer of acoustic plasterboard. We then plastered over the top. We did use some expanding foam in a few points on the brick wall behind the stud frame to stop the bounce in the wall. I now know that wasn't a good move. :S

After the work was completed, we later found that we could still hear voices in the upstairs bedroom that I suspect was emanating from the neighbours’ downstairs living room. Sound must bounce up the party wall. I’m hoping that this will be improved when we repeat the soundproofing process in the other bedroom and living room as there will be more holes/gaps in the brick wall that we can cover up.

I now want to make some improvements for the sound proofed walls in the other two rooms. My proposal is:

  • Remove dot and dab plasterboard
  • Fill any holes in brick wall or on joists in the floor with cement (rather than expanding foam)
  • Build a stud frame 15mm away from the brick wall but use 3"x 2" instead of 2"x 2". Also put some rubber strips on the sides of the stud frame that is in contact with the floor, ceiling and side walls.
  • Fill stud frame with a denser and thicker rockwool this time (75mm with 60kg density rather than 50mm with 45kg density).
  • Sheet with acoustic plasterboard
  • Add tecsound 50 over the plasterboard
  • Sheet with another layer of acoustic plasterboard
  • Plaster wall

I've reached out to soundproofing companies and they have all suggested that using a resilient clip system on top of the new stud frame would be worthwhile but that takes the cost of materials to more than I want to pay. Is it really required if we are building a new wall? Does my proposed build sound reasonable? At this stage I just need to block the muffled voices from entering my house.

The wall in the living room is approx. 7.5m by 2.4 and the bedroom walls are 3.6m by 2.3m

I am a complete amateur, so any advice is greatly received.

It sounds like you have a pretty good handle on what’s required. Isolation, Mass, Damping, and Absorption.

Resilient clips provide isolation, which you’re already achieving, building your studwork away from the wall. IMO, it would be overkill.

I think your idea is sound.

It is always difficult, trying to determine exactly where sound is getting through, particularly when you don’t have access to the source to experiment with moving it around.

In semi-detached properties, two of the most common culprits are chimneys/fireplaces (even when boarded up), and shared joists, where a ceiling or floor joist spans both properties. Nothing you really do about the latter, if present, but the former can be mitigated somewhat if you’re not using you chimney/fireplace, but every situation is different - however, it seems you have a decent grasp of what might be required, should that be the case.

As you’ve already surmised, make good any holes in your brickwork, build your studwork stood off from that wall (using 3x2’s), fill cavity with Rockwool slabs (Wickes sell bales of specific sound absorbing Rockwool - which I used in my cinema - it’s excellent, though has increased in price somewhat since I bought it several years ago)!

Use the same Rockwool to stuff between your floor joists leading up to the party wall.

Using two layers of acoustic plasterboard & Tecsound, will give you plenty of mass, and some damping too.

TL;DR

You're on the right track - and if this doesn’t work, nothing will!
 
Thanks for your feedback, it gives me encouragement that I am on the right track.

I'm still undecided on using a clip system or not. It's approximately another £600 on materials. I've received a couple of quotes and the costs are roughly £2200 for one of the clip systems for the two walls (not including timber and I'd also have to pay a plasterer). I'd rather pay the extra now if it's guaranteed to make a big difference but I'm not sure I will be able to get that.

I'm hoping to cut costs by shopping around a bit as well. I'll probably just get the plasterboard from a local builders merchant for example.

When laying rockwool on the floor 1m back from the wall, would I just place one slab down, or does the cavity have to be filled completely? I think I read somewhere that the rockwool doesn't work well if it's squashed in and compressed but I could be mistaken.
 
Thanks for your feedback, it gives me encouragement that I am on the right track.

I'm still undecided on using a clip system or not. It's approximately another £600 on materials. I've received a couple of quotes and the costs are roughly £2200 for one of the clip systems for the two walls (not including timber and I'd also have to pay a plasterer). I'd rather pay the extra now if it's guaranteed to make a big difference but I'm not sure I will be able to get that.

I'm hoping to cut costs by shopping around a bit as well. I'll probably just get the plasterboard from a local builders merchant for example.

When laying rockwool on the floor 1m back from the wall, would I just place one slab down, or does the cavity have to be filled completely? I think I read somewhere that the rockwool doesn't work well if it's squashed in and compressed but I could be mistaken.
Fill the cavity. You’d be hard pushed (scuse the pun) to compress rockwool enough to stop it being of any benefit.

That’s not to say you should deliberately compress it tightly, but make sure the cavity is filled - if you leave a gap, just like water, sound will find a way through.

The idea is to create a barrier that the sound energy has to ‘work’ it’s way through - transferring energy in the process. In the case of Rockwool, the sound energy excites the strands, converting into heat energy (we’re talking minuscule amounts), and effectively reducing the volume of the sound being transmitted. As long as the strands can still move, even minutely, it’ll be effective.
 
Thanks. I'll get that done in the room we have worked on so far and also do the same in the other two rooms.

For info', I've attached a couple pics of the gaps in the wall under the floor. We used expanding foam to fill them but will use cement in the other rooms as I was advised it's a thicker material so should block sound better.
 

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Thanks. I'll get that done in the room we have worked on so far and also do the same in the other two rooms.

For info', I've attached a couple pics of the gaps in the wall under the floor. We used expanding foam to fill them but will use cement in the other rooms as I was advised it's a thicker material so should block sound better.

Certainly cement will have much more mass than expanding foam, so yes - all things being equal, will perform better.
 
Thanks again.

I got some further feedback on my proposal from one of the soundproofing companies that it will be good for airborne noises but not so much for impact / vibration noises as I have no resilience. The clips and furring bars help with loud impact / vibration noises.

Thoughts on that? It makes me think I should maybe go ahead and buy clips and bars but I also appreciate these companies are out to sell products.
 
Thanks again.

I got some further feedback on my proposal from one of the soundproofing companies that it will be good for airborne noises but not so much for impact / vibration noises as I have no resilience. The clips and furring bars help with loud impact / vibration noises.

Thoughts on that? It makes me think I should maybe go ahead and buy clips and bars but I also appreciate these companies are out to sell products.

Certainly isolation will help with preventing impact noises transferring - I'm just a little wary of what else the resilience bars and clips will add to an already 'isolated' wall.

I guess, as your wall will be attached at the top/bottom/sides, it's not completely isolated - so there may be some benefit. How much? I don't know - as with all things, at some point you get into diminishing returns.

At the end of the day it may be worth spending another £600 now - you certainly can't retrofit the clips. YMMV 🤷‍♂️
 
Another question, apologies!

I'm now starting to question if I can afford to lose 120mm off the bedroom for the soundproofing. Does anyone have any experience of the direct to wall clip systems? That would only take up around 60mm which is much better for that room.

Thanks
 
Another question, apologies!

I'm now starting to question if I can afford to lose 120mm off the bedroom for the soundproofing. Does anyone have any experience of the direct to wall clip systems? That would only take up around 60mm which is much better for that room.

Thanks
I don't have any direct experience - but if you're going to use a clips and channel system, then there is no need to build studwork off the existing wall - the clips and channels will provide the isolation.

That is my understanding anyway - the people selling you the clips should be able to advise.🤞
 
Thanks, I'll give them a shout and see what they advise.

On the direct to wall systems, they suggest sticking 25mm of rockwool to the wall before sheeting with plasterboard. Does the lack of an airgap between the wall and plasterboard cause any issues?
 
Thanks, I'll give them a shout and see what they advise.

On the direct to wall systems, they suggest sticking 25mm of rockwool to the wall before sheeting with plasterboard. Does the lack of an airgap between the wall and plasterboard cause any issues?

No idea! 🤷‍♂️

But as yours is a wall adjoining someone else's property, I don't think it'd cause a problem in the way an outside wall might. That's just my thinking though - I have no evidence to back this up!
 
I've ordered some material to do a direct to wall system in the two rooms. I decided that I can't really afford to lose much space as the rooms are already quite narrow.

Really hope it makes a good difference.

I'll remove the existing dot and dab plasterboard then do the following:

  • Fill any gaps in the brickwork with cement.
  • Add reductoclips to the wall. Attach furring bars.
  • Glue 25mm rockwool to the wall in between furring bars.
  • Screw 15mm acoustic plasterboard to furring bars.
  • Apply sheets of tecsound 100
  • Screw on another layer of 15mm plasterboard.
  • Plaster.

Hoping the above does a decent job. I'll try to limit sockets where possible and deal with side walls as best we can.
 
Air gap helps, especially with low frequency sounds. If you do any sockets, consider fitting putty pads behind.
 
I got quotes from three companies that each sell the products you mentioned. Reductoclips seemed the most expensive system but they are slightly slimmer and the company get very good reviews online (soundproof company). I've spoken to them over the phone and they have been very helpful.

I'm planning on fitting the system on the livingroom next weekend, so will report back.
 
 
I removed the dot and dab plasterboard from the livingroom yesterday (messy job). I can see lots of holes/gaps in the brickwork which I will fill in.

There is also a gap between the brickwall and the side walls, floor and ceiling. What would be the best way to deal with this gap? Fill with cement? The side walls are dot and dab, so I wondered if packing with cement might help reduce the sound that gets in there. When you see the gaps in the ceiling, it's no wonder sound travels from downstairs to upstairs so easily. Some of this I'll need to fix from the upstairs bedrooms I think.

I've attached some pictures.
 

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The soundproofing materials arrived today and were very heavy. I assume it's safe to put the heavy weight onto the party wall? I spoke with the company and they confirmed they haven't been aware of any issues ever occurring. I also spoke with a couple of tradesmen I know and they both said it was sound.
 
It's two 15mm accoustic plasterboards with tecsound 100 in the middle. Is that acceptable on the supporting wall? I'm assuming it's fine as the company sells this as their standard direct to wall system but getting last minute jitters.
 
I would fill with cement. I had a wall just like this. I took the bonding plaster off when I took out the chimney breast exposing holes in the brickwork. This made the sound leakage noticeably worse so filling with cement should work well.
you can then consider anything over the top, soundproof boards, that green slim stuf etc.
 

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