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FLintonRice 03-11-2008 04:23 PM

Soundproofing a Semi party wall
I have purchased a semi-detach that was originally built in 1924. In the process of gutting it and have noticed that I can hear my neighbours perfectly. I know their kids name and who is on the phone when the kids answer. Thing that ticks me off is that they had done a full reno a few years back and had done nothing in the way of soundproofing and may have even decreased the soundproofing properties of the party wall (exposing brick).

Regardless, its my turn to do renos and it needs to be addressed. I believe that the houses are currently separated by two layers of brick. On either side (for the most part) there is plaster over the brick. The plaster is hard to remove and when you do and try and remove it - its not too hard to remove the brick as well, as its somewhat brittle. The party wall runs the length of the house on the left side. The stairs go up the left side as well - so framing with 2x4's is not ideal as my stairwell will be wide enough for bulemics only.

The idea (which I encourage you to shoot down is the following:

1) Screw 5/8" drywall directly into the plaster brick.

2) Attach a second piece of 5/8" drywall to the first and put a tube of Green Glue between the two.

An alternative is to attach resilient channels to the brick/plaster and put the dywall on the channels.

My concerns are:

a) Fire code - this is essentially a firewall so is direct attachment allowed?
b) Could the weight of two 5/8" sheets ever be supported on screws into brick?

Sorry for the long post and if you've gotten this far - thanks for reading it!:thumbsup:

Ron6519 03-11-2008 10:44 PM

A few questions.
What is plaster brick?
What is Green Glue?
In order to reduce sound from next door, the resilient channels you mentioned would be better then the other choices.
Offsetting framed walls with insulation would be better, but take up more room. A compromise would be a single framed wall, built away from the common wall and insulated might be the best option. I don't know if a spray foam insulation would be better then batt insulation for sound deadening.

FLintonRice 03-12-2008 10:12 AM

I meant plastered brick - not plaster brick. That would be about an inch of plaster over brick.

Green glue is a sound dampening substance (comes in tubes much like caulk). It is put between drywall to add sound dampening properties. It is not an adhesive as the name would indicate. With 2 5/8" sheets and Green Glue - you can achieve above STC 60 on a framed wall.

I am not sure that you've answered the question. I know that I can build a frame but that would (as indicated) reduce the width of the stairs which I definitely do not want to do. Spray foam (although a favourite of Mike Holmes) is not known for soundproofing and as I've read, you want mass to stop sound not low density foam/batt. Also the resilient channels were in addition to the 2 5/8" sheets - not an alternative.

Perhaps this is not a question for DIY'ers.

Ron6519 03-12-2008 11:00 AM

Try giving these guys a shot.


jerryh3 03-12-2008 02:41 PM

Try this website:

centurysemi 04-03-2008 01:48 PM

I am curious to know how your wall turns out as we have the same problem (stairway and all) and are having trouble finding ways around it. So far, we have attached metal furring strips to the walls, put rigid foam insulation in that small space, and then drwalled over top. While there has been a slight improvement, I cannot say it's significant. However, we have not caulked the baseboards etc yet. I have looked in to Green Glue and it does sound promising - if you go that route please let me know how it turns out. In the meantime, i can tell you that just adding drywall is not worth it.

Brik 04-04-2008 08:29 AM

Flinton - I'm following you.

You would need to check with your local code guys to confirm your code question.
As for attachment to brick. Yes, the brick can hold the weight but I am of the opinion you do not want to do this. It would be a huge pain to use, say tapcons, for hanging drywall. Ug.

You will want to fir out the wall and attach your drywall to that. Better for soundproofing use your resilient channel then drywall into that.

Is there any reason you couldn't move the stairs out a bit to accommodate a beefier wall?

peace_and_quiet 04-10-2008 09:47 AM

Glad I found this thread. I've got a similar problem--live in a city in an old rowhouse, and the only separation between the neighbor and myself is two layers of brick and some plaster. At this point, I want to be able to block (as much as possible) the conversation, TV, and yelling/singing that goes on next door.

What I'm planning is to tear down the plaster and expose the brick, then hammer in 1*3 ferring strips. On the strips, I'm going to attached Quiet Rock insulated drywall (the 510 variety). The new wall should only be about 1.5 inches wide (and inch for the strips, half and inch for the quiet rock). The rep for QuietSolutions said the Quiet Rock would likely cut the sound transmission by at least 65% or so (without doing anything to the ceiling or floor). Sounds like a relatively effective and straight forward solution.

Anyone have any opinions or experience with this? The quiet rock seems like it will be the easiest/quickest option that will still be effective.


Brik 04-10-2008 10:34 AM

The insulation wont help much compared to otehr solutions. No reason to remove the old plaster, its helping. Best to build a wall NOT attached to the party wall. When building that wall attached drywall on both sides of the studs for even better sound isolation. I would do double drywall before spending on any insulating.

Ron6519 04-10-2008 11:18 AM

I saw this problem on a Holmes on Homes show. They used a sheetrock with a metal sheet layer in the middle. It cut down sound transmission substantially.

peace_and_quiet 04-10-2008 11:38 AM

I should clarify--when I said 'insulated drywall' I meant the sound dampening variety.

I have to keep whatever wall I build wall relatively thin, as the moulding for a door frame is only a couple inches from the original brick wall. Given the little amount of working room available, I need to use it as effectively as possible.

I think the two options are either ferring strips into the brick, then sound dampening drywall (Quiet Rock) into the strips. -OR- ferring strips into the brick, that two sheets of 1/2" drywall with Green Glue in between them. From the research I've done, the sound damening drywall and the green glue option both (theoretically) perform about the same.

As much as I'd like to keep the plaster, it's eating up 3/4" of potential wall...

If anyone has tried either of these, I'd appreciate it if you could share the results.

peace_and_quiet 04-10-2008 01:49 PM

Just as a follow up, that Holmes and Homes episode was called 'Wall of Sound,' and you can find it on youtube. The drywall they used in the show is the Quiet Rock stuff I was talking about...

centurysemi 04-10-2008 02:42 PM

Peace and Quiet - just a tip: you may not have to take down the plaster. We discovered ours was not lathe and plaster (like on all of our other walls) but just a sand and lime plaster skimmed over the brick. Turns out it was taking up about 1/8" of space, and I think Brik is right that it is helping block the it's a very messy job taking the plaster down! Do a small test area to see first. Let me know how the quiet rock turns out!

jogr 04-10-2008 03:41 PM

I'm pretty sure that mass only blocks low frequency sounds. You already have a great deal of mass in a brick wall so adding two layers of drywall to increase mass will do almost nothing. It's the high frequencies you need to work on.

Resilent channel, green glue, sealing all openings will all help block the high frequencies. Rigid foam board actually transmits sound well (like a drum) so that won't help. The mass of Quietrock won't help because you already have mass but it may have vibration dampening material (like green glue) between it's layers that might help.

If it was my wall I'd probably go with attaching furring strips to the brick and then green glue and 1/2" drywall. Then seal every opening.

jason h 04-10-2008 09:36 PM

the mass of concrete or brick is different than the mass of drywall.
we build a lot of condos and we use either resilent channel and quite rock or we use shaft liner which is 2 one inch thich sheets of drywall actualy intended for fire seperating ,but sound control qualities are very good.
with that said , i would still recomend resilint channel

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