Soundproofing

fatherdougalmag · 19-08-2003 3:31pm #1

Any soundproofing buffs around?

We're trying to soundproof our main bedroom against noise from next door (it's a long story). It's due to be done in a couple of weeks but I'd appreciate any advice which people could pass on.

We're in a typical semi-d with the front doors on opposite ends of the 2-house block. The sitting rooms are beside each other divided by the semi-d dividing wall. The main bedrooms are above the sitting rooms. Needless to say, we're predominantly focusing on the dividing wall in the main bedroom. On that front, we're getting about 6 inches added to the existing wall. Rockwool will be used here. I have read elsewhere though that it is important for this new wall not to make contact with the existing wall otherwise the sound will just be 'conducted' through whatever is used. I'll bring that up with the installer.

What I'd like to discuss though is the floor. We have sanded, varnished T&G floorboards. We'll probably have to get carpet down with double under-lay. If we had the money, we'd probably pull the floorboards up and put something down but on the basis that any sound from next door would be entering the floor cavity from the dividing wall joint, what could we do to enhance the effect of soundproofing here?

For example, before we install the double-wall could we put something (more rockwool?) underneath where the floorboards meet the dividing wall?

Any tips greatly appreciated

Victor · 19-08-2003 9:17pm

There are a few different principles in sound proofing and a combination works best.

Mass - a very very wall needs a huge amount of energy to make it vibrate, but at the same time solid matter tends to conduct sound well.

Separation - by setting up separate layers in the construction sound can't be conducted across the cavity(s).

Sealing - a 3% air cavity can double sound penetration through a standard door.

Refraction - sound will easily refract around edges. Used to break up motorway sounds.

Reflection - hard surfaces will reflect well, soft surface won't.

Disruption & reflection - creating a cavity of about one half (?) of one wavelength will first reflect and then cancel out the soundwave. thsi si used in "triple glazing".

The idea of extending the wall by the 6 inches is to create a cavity and then use a lot of mass in the new partition (say 3 layers plater board).

For the floor / ceiling you could install a second set of joists. This means taking down ceiling or raising floor (really awkward). Also add a resilient layer (3mm packing foam) between bedroom floor boards and joists. All this make it difficult for impact sounds (especially) to be transferred. Adding rockwool in the floor cavity will increase this effect for other sounds. Adding mid-/deep-pile carpet to the sexcave^H^H^H^H^H^H^H bedroom floor will add to the effect.

Make sure all joints are sealed in soft silicone. Make sure the new structure contacts the existing as little as possible. Where it does contact, a resilient layer should be added.

fatherdougalmag · 20-08-2003 10:04am

Thanks for that Victor. I'll at least pass on the tips to our installer.

Just one question regarding:

All this make it difficult for impact sounds (especially) to be transferred.Adding rockwool in the floor cavity will increase this effect for other sounds. Adding mid-/deep-pile carpet to the sexcave^H^H^H^H^H^H^H bedroom floor will add to the effect.

When saying 'add to the effect' I take it you mean the effect of soundproofing (i.e. rockwooling and carpeting are a good thing). I like the idea of using packing foam to insulate structures from each other. Again, I'll put this to the installer.

I haven't given that much concern to the ceiling. Should I? I guess just popping my head into the attic when there is noise will give me an idea of how much noise in spilling over across the top of the dividing wall. We did, however, have the builders come in and block off any gaps so it probably isn't that much. Just for the sake of completeness can you comment on ceiling insulation? I've read that rockwool can be used with/instead of the fibreglass insulation but that the improved heat insulation would mean that the plumbing in the attic could be prone to frost in cold weather. We could, however, just insulate the pipes or leave the attic door open a little bit.

Thanks once again

Victor · 20-08-2003 2:09pm

Originally posted by fatherdougalmag
Thanks for that Victor. I'll at least pass on the tips to our installer.

No problem, are you not getting a "professional" to do it?

Originally posted by fatherdougalmag
When saying 'add to the effect' I take it you mean the effect of soundproofing (i.e. rockwooling and carpeting are a good thing).

Yes, adding to the soundproofing effect. Let us say a heavy object hits the floor boards, noise would then be easily transferred into what is after all a relatively light structure (joists, floor boards and ceiling plaster, but mostly air) and this makes the sound readily transferable. Do the same with the carpet and the energy transfer isn't quite so efficient as the thickness of the carpet means the object first has to crumple the carpet. Likewise the multitude of edges in the rockwool refracts the sound massively, reducing is from a "single" loud sound to a more spread out, quieter sound. Likewise the sound reflected back into the room is spread out and not a single loud sound (the carpet would have a similar effect to what frosted glass (or a frosted section of mirror) would do to light). Make sure all the floor boards are fitted tight, add a few extra screws (not nails) if needs be.

Originally posted by fatherdougalmag
I like the idea of using packing foam to insulate structures from each other.

There are specific products out there - ask in a floor boarding shop / builder’s providers for a "resilient layer" foam (sometimes a cardboard-type product is used). It’s a spongy foam, typically about 3mm thick.

Originally posted by fatherdougalmag
I haven't given that much concern to the ceiling. Should I? I guess just popping my head into the attic when there is noise will give me an idea of how much noise in spilling over across the top of the dividing wall. We did, however, have the builders come in and block off any gaps so it probably isn't that much. Just for the sake of completeness can you comment on ceiling insulation? I've read that rockwool can be used with/instead of the fibreglass insulation but that the improved heat insulation would mean that the plumbing in the attic could be prone to frost in cold weather. We could, however, just insulate the pipes or leave the attic door open a little bit.

The ceiling / attic really depends on the house in question. Are the party walls (between you and your neighbour(s)) of solid construction? If not, build / seal them up.

Are there other rooms upstairs that you need to exclude the noise from (including stairs / corridor)? You best bet here is to insulate all of the rooms (100mm sound insulation on all the rooms is worth more than 200mm on your room only – that said 200mm won’t be twice to cost of 100mm to install).

I would add the rockwool to any existing insulation as opposed to replacing it, unless it is in poor condition.

For the plumbing, it is easy enough to buy shaped foam insulation, which you can fix in place with plastic ties. If possible put your rockwool insulation above the pipes, not under. If you insulate the water tank(s), don’t insulate underneath it, but allow some warmth to seep up from the house to prevent freezing tanks / pipes in winter. You could also insulate between the (sloping) rafters as opposed to (horizontal) joists. Be very careful when fitting insulation to your attic that it is properly ventilated – otherwise you are at risk of causing condensation and / or dry/wet rot.

One further option to protect against flood with a burst/frozen pipe is to fit a tray under the tank and pipes.

fatherdougalmag · 20-08-2003 2:32pm

Originally posted by Victor
No problem, are you not getting a "professional" to do it?

We're getting a sound-proofing guy to do it alright. He has worked in cinemas and he has done domestic work as well. He came recommended.

Originally posted by Victor Do the same with the carpet and the energy transfer isn't quite so efficient as the thickness of the carpet means the object first has to crumple the carpet.

Understood. You recommended a deep pile carpet. It's been a while since we looked at the price of carpet but would another solution be to use a double-layer of underlay? We've heard that there might be a special kind of underlay available as well.

Originally posted by Victor Make sure all the floor boards are fitted tight, add a few extra screws (not nails) if needs be.

Is that just to prevent creaking floorboards or are nails more prone to conducting sound? I have a concern as to how the new wall might be affixed to the existing wall. Someone tells me of a recent Sunday Tribune article dealing with sound proofing indicated that this was a common pitfall. Maybe it wasn't the nails themselves. It was probably just the fact that the studding in the new wall was in contact with the existing wall and that just conducted the sound through. If this is the case, could a resiliant foam/cardboard layer be applied to the wall where the new stud-work would make contact with the existing wall?

Originally posted by Victor There are specific products out there - ask in a floor boarding shop / builder’s providers for a "resilient layer" foam (sometimes a cardboard-type product is used). It’s a spongy foam, typically about 3mm thick.

We'll add that to the shopping list.

Originally posted by Victor The ceiling / attic really depends on the house in question. Are the party walls (between you and your neighbour(s)) of solid construction? If not, build / seal them up.

As far as I can see the wall is constructed of oblong concrete blocks about 6 inches thick. The studded walls are then mounted on to these. We suspect that the sound is coming through the wall from next door via the studded wall/plasterboard on their side, the concrete blocks and the studded wall/plasterboard on our side.

Originally posted by Victor Are there other rooms upstairs that you need to exclude the noise from (including stairs / corridor)?

There are two bedrooms adjacent to the party wall. The one I have been talking about so far is the main bedroom. The other room is a spare room (for the next few years anyway). We will be giving that the same treatment anyway.

Originally posted by Victor I would add the rockwool to any existing insulation as opposed to replacing it, unless it is in poor condition.

OK. We'll only do this though if we feel necessary. It should be simple enough to do as a follow-up action on my part.

Once again, thanks for the invaluable advice. I'm beginning to enjoy this

Victor · 20-08-2003 3:04pm

Just a question what type of noise problems are there from next door?

Originally posted by fatherdougalmag
You recommended a deep pile carpet. It's been a while since we looked at the price of carpet but would another solution be to use a double-layer of underlay?

Fair enough if the carpet fitter is happy you (rather the carpet) won't end up with stretch marks then work away. My point is to not use el-cheapo horsehair carpet with no resilience.

Originally posted by fatherdougalmag
Is that just to prevent creaking floorboards or are nails more prone to conducting sound?

A loose floor board will creak, but in the event of a bang, the floor board will reverberate more than it would otherwise. The point of screws -v- nails is that screws are much less likely to come loose. This means better fitting floor boards and plaster panels (walls & ceilings).

Originally posted by fatherdougalmag
I have a concern as to how the new wall might be affixed to the existing wall. Someone tells me of a recent Sunday Tribune article dealing with sound proofing indicated that this was a common pitfall. Maybe it wasn't the nails themselves. It was probably just the fact that the studding in the new wall was in contact with the existing wall and that just conducted the sound through. If this is the case, could a resiliant foam/cardboard layer be applied to the wall where the new stud-work would make contact with the existing wall?

Ideally the new sound partition won't touch the existing wall, however if it is a large flat area, it would need to be that little bit sturdier. I would sooner introduce double "studs" (verticle joists) or introduce a return in the wall than brace it against the existing.

Originally posted by fatherdougalmag
As far as I can see the wall is constructed of oblong concrete blocks about 6 inches thick. The studded walls are then mounted on to these. We suspect that the sound is coming through the wall from next door via the studded wall/plasterboard on their side, the concrete blocks and the studded wall/plasterboard on our side.

I meant in the attic. Your party wall should be ~9 inch (~225mm) blockwork. Are you saying that the party wall between bedrooms is timber? Is the house timber framed?

fatherdougalmag · 20-08-2003 4:07pm

Just a question what type of noise problems are there from next door?

The 'usual' loud TV, over-active kids at night. We've asked politely, the Gardaí have asked politely but they don't seem to know the meaning of the words peace and quiet. My main concern is their sub-woofer. I guess sub-woofer would be a mix of impact and air-borne noise?

My point is to not use el-cheapo horsehair carpet with no resilience.

We'll certainly use the best, affordable carpet and ask the supplier about sound-proofability characteristics.

I would sooner introduce double "studs" (verticle joists) or introduce a return in the wall than brace it against the existing.

Could you explain a little more about double studes? I would imagine our chap will employ a typicall stud configuration where there are gaps of about 30cm between each vertical stud and then horizontal studs between two adjacent vertical studs. Where does the double studding come in? Would double studding not increase the contact area between the existing and new walls.

What do you mean by a 'return in the wall'?

Your party wall should be ~9 inch (~225mm) blockwork.

I'm sure there must be a standard brick size that's used. 6 inches was just a guess. I'll ask one of the builders to be sure.

Are you saying that the party wall between bedrooms is timber? Is the house timber framed?

The party wall is concrete block-work. It's a regular semi-d construction.

I've attached a JPG showing the first floor bedroom layout of the two semi-detached houses. We live in the righ-hand side semi-d. The bottom of the picture is the front of the house; the top is the back. Our main bedroom is the highlighted box at the front of the house (bottom of the picture). The room immediately behind this (on top in the picture) is the other (spare) room we're getting done.

Borzoi · 22-08-2003 12:05pm

Originally posted by fatherdougalmag
The 'usual' loud TV, over-active kids at night. We've asked politely, the Gardaí have asked politely but they don't seem to know the meaning of the words peace and quiet. My main concern is their sub-woofer. I guess sub-woofer would be a mix of impact and air-borne noise?

TBH the subwoofer noise will be the hardest to absorb, as low frequency sound needs a very heavy mass to interfere with it.

Before you go to all the expensive, have you talked to your local council environmental officer about the noise, he may be able to help you out.

BTW is your neighbour owning or a tenant, just thinking long term

MrHappy · 22-08-2003 12:22pm

I also have the same problem

, (The house next door has wooden floors as well), kids thumping up and down the stairs (which is next to our bedroom and the main room downstairs). Doors banging etc..etc..etc.. and what sounds like marbles crashing on floors..... (I know their kids, but it can get a bit much).

Is it very expensive to get this sort of thing done. (I dont have a clue about this type of stuff)

Cheers!

Victor · 22-08-2003 1:13pm

fatherdougalmag, I just remembered, look into insulated attic acess hathches.

Originally posted by MrHappy
Is it very expensive to get this sort of thing done. (I dont have a clue about this type of stuff)

I suspect you are talking about a little more than €1,000 per room, extra to do the ceiling. Remember you wil be loosing 6-8 inches (150-200mm) from your room.

fatherdougalmag · 25-08-2003 1:18pm

Originally posted by Borzoi
Before you go to all the expensive, have you talked to your local council environmental officer about the noise, he may be able to help you out.

We've looked down that road and it can be costly (both emotionally and financially). So we've decided that we're probably just as well to put the money into getting something definite done about it.

Originally posted by Borzoi
BTW is your neighbour owning or a tenant, just thinking long term

They own the property. Again, we're aware that the soundproofing might not be 100% effective but it will definitely be an improvement. Thing is, if we were to consider moving it would have to be to a detached house this time and that means buying outside Dublin. We've just moved here after living in Kildare and, with 2 kids involved, that's a major enough task as it might well involve moving school, minders, etc.

At the end of the day, there's a great injustice being done when the innocent party has to move. The irony is that there's an audible silence with regard to legislation. Take a civil action and cross your fingers. And there's always the risk of fallout when taking these sorts of actions against a neighbour.

Borzoi · 25-08-2003 2:16pm

Fair enough mate, good fences = good neighbours etc.

You're obviously going in with you eyes open, hope it works out for ya.:)

Capt'n Midnight · 05-09-2003 10:40pm

Probably not a lot of use but...

Anti-noise - you setup a mic at the wall and some speakers - the idea is that you cancel out the noise buy having the same sound come out the speakers but in anti-phase. Works best with predictable repetitive noise - eg: used in helicopters.

[i4i] You could always play back a recording of thier noise - all that'll do is make you feel better -- maybe.. Or I take it you are early birds compared to the neighbours - perhaps a startup a few subwuffers first thing in the morning to tire them out. (low frequency so it's hard to tell where comming from and more of a subliminal thing) [/eye for eye]

ear plugs are not recommended as an option... - not good for your health.

Eh.. maybe you could drop in a small bottle of wax softening drops - it could be a simple problem of deafness as opposed to insensitivity - Or drop in lots of estate agent ads....

Best of luck - and lots of soft wall furnishings - thick curtains... (reduce reflections)

slave1 · 05-11-2003 9:57am

how did this turn out in the end??

fatherdougalmag · 05-11-2003 11:55am

Still haven't gotten around to it but it'll be happening soon. Just had a friend in the trade come around and see what materials we need. The plan is largely unchanged: first of all take up a few floorboards and fill in the gaps around the joists (if any) with rockwool. Mightn't make a big difference but it's better than nothing. We're going to use a steel studded frame work. Didn't know about this stuff until he told me about it. Does the same trick as wood but a lot easier to work with. We're going to use 100mm rockwool behind/inside the studding and then lay two layers of plasterboard ensuring that the gaps on the first layer are not exposed. Generally, then, fill any gaps with mastik (and apply mastik wherever the new work meets the existing structure). Of course, this new wall will not meet with the existing wall.

ropez · 15-03-2008 5:44pm

interesting thread, it just popped up on google while I was seaching for DIY related information - - just curious to know the outcome 5 years on.... ?