New build A2 rated house party wall

gallagbr

Hi, we recently bought a brand new A2 rated semi D house. We love the house but we hear muffled chatter and TV coming through the Party wall.

When we were buying the house the estate agent and developer made a big deal about the fact that the party wall was a cavity wall so noise transfer would be less than is typical. However it seems to us that having lived in semi d houses previously this approach is worse than that of a standard party wall consisting of 100mm block on the flat. The builder says that the wall complies with Section E of the regs however this assertion does not fill me with joy given the fact we can hear our neighbours chatting (at normal conversation volume) all the time and given the historical issues with regulation in the construction industry in this country I am looking for answers elsewhere.

The cavity between the party wall leaves is empty and both of the cavity party wall leaves are plastered with sand cement render and then dry lined internally with 2 inch battens and plasterboard. Might it be that the void beteeen the render and dry lining PB is amplifying any noise that transfers through?

Has anyone any ideas on how to improved the soundproofing as I’m sure it’s not normal? Thanks

Mellor

The cavity is not going to amplify the sound. (cavities are how most acoustic glazing works for example). But a 300mm cavity is not going to be a better performance than a block on flat (which is slightly more mass per m2.

I would expect the performance between the two to be dissimilar, if they were constructed well. If this is noticeable worse, I'd be look for weak points. Where the walls have outlets installed, notched for joists. If you want to improve it, the low impact solution is to fill the cavity. Which is very east if it is sealed from the external cavity

gallagbr

Hi thanks for your response. I agree that sound is not being amplified in the cavity between the block work leaves (this is a 100mm cavity, not 300mm). The cavity my question related to was the cavity behind the plasterboard.

I have checked around the sockets etc and it’s not obvious that the noise is any louder in those areas, but thanks for your suggestion.

We have looked into pumping the cavity but one noise expert said it would make the noise worse as it increases the ability of noise to travel across the cavity, whereas I see insulation companies sell such a product for the purpose of filling cavities.

It’s all very strange and difficult to know who knows what they are talking about.

Mellor

https://www.boards.ie/discussion/comment/121361287#Comment_121361287

A 300mm cavity wall is a standard cavity wall. It refers to 300mm total width, not a 300mm cavity - 100mm cavity and 100mm block leafs (more accurately 102.5 for 305 total).

A cavity behind the plasterboard would not amplify the sound either. That's not how cavities work. Do you definitely have a service cavity behind the plasterboard? Not really standard, but if you do then you would discount the possibility of GPOs being chased into the party wall.

I'd question the qualifications, knowledge and experience of that "noise expert" who said adding mass to the cavity would make it worse. His only looking at the sound path and ignoring the extra mass. The net effect is a reduction. I'd want to have block plans to understand what happens are the external wall junction to go that route.

gallagbr

https://www.boards.ie/discussion/comment/121365595#Comment_121365595

Yes, I understand that a 300mm is a standard cavity wall. I'm not sure I agree that the cavity behind the plasterboard would not amplify sound. I have read that empty cavities can cause a 'drum effect' when noises enter an empty cavity. It seems to me that it is the plasterboard that is amplifying noise as the entire wall seems to create almost a surround sound effect.

There is definitely an empty service cavity behind the plasterboard, about 50mm wide. There are no other penetrations in the party wall either (joists run parallel to the wall). There were no 'block plans' created - the builder said he worked off levels and 'typical details' drawings which I do have and append an extract from below showing the interface between the external front wall (running horizontal) and the party wall (running vertically).

Gumbo

What is the construction method of the houses?

Even the new Part E Sound will still transfer sounds. It will never be silent unfortunately.

gallagbr

https://www.boards.ie/discussion/comment/121365774#Comment_121365774

Sorry I don't understand what you mean by the 'construction method'? I realise it will never be silent however I would have expected it to be better. As previously mentioned, we have lived in older Semi-D houses before and heard very little noise through party wall.

sydthebeat

Could you download a sound meter app such as this:

https://play.google.com/store/apps/details?id=com.gamebasic.decibel

and let it run a few times for 10 minute intervals during the evening and see what the results are.

It's possible your older house could simply have had a better party wall construction and quieter neighbours.

10-10-20

OP have you had an opportunity to investigate the wall construction at all (by drilling into it) or are you relying on drawings and here-say from the builder?

A few things which come to mind are that if it's double-leaf cavity (and not cavity-block) then there will be steel wall-ties going from leaf-to-leaf every ~60cm's which will transfer the sound energy through the wall then out into the battens and into the plasterboard. There isn't any physical decoupling in that make-up and that's partially why a retro-fitted correction here is difficult. Plus if the joists are mounted into the blockwork (through small voids between the blocks rather than using joist hangars) then you could have a situation where the joists from your ceilings are in contact with the joists of next-door, or are even touching the joists protruding from next-door. All of those reasons could be why you're getting this "surround-sound" effect as the sound is being carried through the fabric of the walls and ceiling.

I can't thought see why pumping the cavity is not going to improve the situation in some way though; except we have to bear in mind that due to the wall-ties and potential joist issues, you're only going to attenuate (lessen) a subset of frequency ranges and you might end up with better clarity in other ranges - maybe that's what the "noise expert" was referring to?

Anyway, I'm only a bystander and the other guys in this thread know far more on this subject. 👍️

gallagbr

https://www.boards.ie/discussion/comment/121365872#Comment_121365872

Hi, Yes I was on site during the construction of the party wall and at various points up until the plasterboard was fixed so I know it was built according to the drawings. It is definitely a standard 300mm cavity wall built with standard metal wall ties. As I mentioned previously, there are no joists supported from the cavity wall - we don't hear any noise from next doors floors such foot steps - just their voices and TV.

10-10-20

https://www.boards.ie/discussion/comment/121365891#Comment_121365891

Ok, sorry I missed the comment earlier. Good that you have the specific details on the make-up. I suspect must of the noise transfer is through the wall-ties and as per Mellor a denser wall (block on flat) would have achieved better attenuation. I wonder would looking for a pumped insulation product with the highest density be the best option (PS bonded-beads/closed-cell/open-cell, or maybe blown cellulose given that it's an inner-wall...)?

sydthebeat

So it's ambient noise then that is traveling across, not impact sound.

You are correct that voids behind plasterboard slabs on concrete walls will amplify sounds (it's probably better to compare to how an acoustic guitar makes its sound, as drum requires an impact first)

I'm a firm believe in quantifying something first (if you can't measure it, you can't fix it) so I'd still be going down the route of making recordings first to see just how much of an issue this really is.

People can develop selective auditory attention over time, which allows then to block out background noises. As you've recently moved into this house, you're noticing the noise much more than you might in 6 months time

bfclancy2

https://www.boards.ie/discussion/comment/121365595#Comment_121365595

Blocks are 100mm, brick are 102.5mm to be precise

Gumbo

https://www.boards.ie/discussion/comment/121365814#Comment_121365814

Timber frame, Metal Frame, Block, Concrete or ICF.

Edit. I see you mention a 300 cavity and only airborne noises in a later post.

I'm not sure anything will really help at this stage. I'm a firm believer of having a dense Party Wall detail, I'm not a fan of the cavity construction in a Party Wall scenario.

The resistance to airborne sound depends mainly on the mass per unit area of the leaves of the wall and on the degree of isolation provided by the cavity. The isolation is affected by connections (such as wall ties and foundations) between the wall leaves and by the cavity width.

Section 3.5 of TGD Part E.

1e211202-4a8f-44ea-95a5-31865fd5fe2a.pdf (www.gov.ie)

gallagbr

https://www.boards.ie/discussion/comment/121366140#Comment_121366140

Yes, thank you. I understand all of that - I was just wondering if anyone had any ideas on how soundproofing could be improved for my circumstances and I think what you are saying is nothing will be of help (which isn't of much help to me).

Gumbo

https://www.boards.ie/discussion/comment/121366232#Comment_121366232

Unfortunately I think that’s correct.

Mellor

https://www.boards.ie/discussion/comment/121365765#Comment_121365765

The drum effect is exaggerated. Also used to describe sound across a hollow stud wall. But it’s incorrect, hollow cavity walls simply don’t have any mass. If it were actually amplify sound would get louder passing through a hollow stud wall.

https://www.boards.ie/discussion/comment/121365927#Comment_121365927

A guitar creates sound by vibration. The strings physically vibrate the body resonating a sound that can only leave through the hole. Sound passing through a guitar body do not get amplified out the back.

The misnomer drum effect refers to vibrations in one sheet being resonated to the other, by passing the cavity. Like in a coconut phone. acoustic double glazed partitions have dissimilar thickness glass so the sheets resonance at different frequencies.

Bit even it it were to happened, the extra mass usually blocks more sound than is transferred, for a net loss. As above otherwise stud walls would amplify everything

Mellor

https://www.boards.ie/discussion/comment/121366232#Comment_121366232

Dense mineral insulation is the best instillation I’ve found for hollow walls. Currently commercial recording studio built in stud, plasterboard and mineral wool. Performs far higher than a block wall - but this wall is huge.

Obviously better to install it first time. Not sure what your options will be for dense blow in will be. Will greatly reduce high frequency sound

sydthebeat

https://www.boards.ie/discussion/comment/121366785#Comment_121366785

https://youtu.be/ST2HCGBvjRc

empty studs walls DO amplify sound.

heres a very simply video to show how simple air cavities amplify sound. All you need is the air gap. Cavities are by definition, air gaps.

i often place my phone on a upturned cup or bowl to make the sound louder of im doing something while listening to my phone.

to put this into the context at hand, no cavity will mean a lower noise. The practicalities and economies at this stage are whats making this resolvable or not.

10-10-20

https://www.boards.ie/discussion/comment/121366898#Comment_121366898

I wonder if this is a job for fine geocell glass foam?

https://geocell.ie/

Or the bubble stuff might be better:

https://geocell.ie/bubble/

gallagbr

https://www.boards.ie/discussion/comment/121366906#Comment_121366906

Hi, thanks for this - makes sense. In terms of improving the sound proofing I'm thinking the easiest approach would be to remove the existing plasterboard and fill the void behind it with acoustic rockwool slabs to reduce any guitar or drum effects created in that void. Then cover over with two layers of acoustic plasterboard with a layer of mass loaded vinyl sandwiched between. I'm just a bit hesitant to blow insulation into the 100mm cavity between the blockwork in case it might cause damp issues but my concern may be unfounded.

Mellor

https://www.boards.ie/discussion/comment/121366906#Comment_121366906

The video shows a sound source vibrating a larger object, a bit different. The cup or bowl does amplify sound, but that doesn't contradict any thing I said. That works by taking sound leaving a source in all directions, and re-directing the waves into one direction (the opening). The sound waves sync up, and increase intensity - this wave principle is literally called amplification. Sound passing through a wall in a single direction does not behave like that. Sound can flank along a cavity, which is a separate issue.

Sound behaves very strangely, so I don't like making generalisations. A particular build up might reduce sound overall, but resonate in the sweet spot for a certain frequency and be worse at that frequency. Some changes reduce high frequency, and increase low. Then there is the truly black magic stuff like sound waves destroying Tacoma narrows bridge, or whispering walls.

But the simplest example is a real world example. An empty steel stud and plasterboard wall is a pure cavity (a double skinned drum). If the cavity resulted in a net amplification of sound as claimed. Then sound would get louder passing through a hollow stud wall into the adjacent room. But obviously that doesn't happen, and amplification that occurs is less than the sound reduction that the mass/void creates. This is clearly demonstrated in test and real world data. A wall like that has an value of about 32Rw, which is not alot.

The real problem with part E is that its very generic in terms of "blocks" and the range of blocks on the market perform very differently

Yellow_Fern

Cavities can amplify sound. Depends on the resonance whether or matters. But I doubt it's the cause here.

The main thing the OP should look for is that parge coat consistently applied.

gallagbr

https://www.boards.ie/discussion/comment/121372736#Comment_121372736

Hi Yellow Fern, thanks for this. How would I check that the parge coat has been consistently applied at this stage? Assuming that the parge coat has not been consistently applied, how should the noise issue be resolved (bearing in mind that the wall allegedly complies with Part E of the regs)? Is it add more parge coat or build a separate properly soundproofed wall next to the cavity wall?