Soundproofing a Wall from Noisy Neighbors

Hearing your neighbor's TV, conversations or footsteps through a shared wall is the fastest way to fall out of love with a townhouse, condo or semi-detached home. It is also fixable, and usually from your own side, without involving the neighbor at all. Below is the approach we recommend day in and day out, followed by real questions from customers with shared-wall problems and our answers.

Why you hear them so clearly

A typical party wall is drywall screwed to studs, and studs are excellent sound conductors. Voices and TV sound shake the neighbor's drywall, the studs carry that vibration across, and your drywall replays it like a speaker cone. On top of that, sound sneaks around the wall through what is called flanking: over the top through a shared attic, under the floor, through back-to-back electrical outlets, and along stairs fastened to the shared wall. A good plan treats the wall itself first and keeps an eye on those side doors.

If you can open the wall (or add a new layer of framing)

The strongest fix is to decouple your side. With the drywall off, mount resilient sound isolation clips and hat channel across the studs, fill the stud bays with ordinary fiberglass or mineral wool insulation, and hang two layers of 5/8" drywall with Green Glue between them. Seal the perimeter and any cutouts with acoustical caulk, and dress outlet boxes with putty pads. To put numbers on it: a bare single-stud wall sits around STC 37, where normal speech is easily understood through the wall. The clip-and-Green-Glue assembly tests around STC 63, where even loud music is reduced to a faint murmur. That is not a small upgrade; it is a different category of wall.

If you cannot open the wall

Plenty of our customers rent, live with plaster walls they'd rather not demolish, or simply do not want the dust. The workhorse option is to add a second layer of 5/8" drywall with Green Glue directly over the existing wall. It is a straightforward weekend project, costs you less than an inch of room depth, and makes a real difference on voices and TV noise. A step up from that is building an independent stud wall just off the party wall and drywalling it, which gets close to full decoupling. Two cautions from the questions below: leave the new framing an inch or so clear of the existing wall, and do not create sealed air pockets between heavy layers, which produces the triple leaf effect and can make things worse.

Check the side doors

If speech comes through crisp and clear after a wall upgrade, sound is probably flanking. Shared attics with an incomplete party wall, ductwork serving both units, back-to-back outlets, and staircases bolted to the common wall are the usual suspects, and each shows up in the customer questions below. The wall assembly above buys you the biggest single improvement; sealing the flanking paths is what gets you the quiet you were picturing.

For ceilings, see our companion guide on soundproofing a ceiling below noisy floors, and for the full method on every surface, our how to soundproof guide.

Real customer questions about shared and party walls

What does going from STC 37 to STC 63 with clips and Green Glue actually mean?

Customer question: in layman's terms what does single stud STC value of 37 vs quiet clip and GG STC value of 63 mean. Can I still hear normal talking, TV and radio on the other side of wall, or percentage wise how much of it is now 'blocked'?

Trademark Soundproofing answer: Hi Curtis. STC 37 you will still hear conversations. STC over 60 is luxury and you should not hear much unless it is very very loud.

Which side of the wall should the decoupling clips go on?

Customer question: Hi, great site, thanks so much!! My questions it: Which side of the wall should the decoupling clips / 2 layers of gypsum with GG be placed? Would it be best to put them in my own bedroom (where I want to reduce noise) or on the other side of the wall (the noisy side) For reference, the wall would be: 2 layers of 13mm gypsum, 90mm timber with fibreglass insulation, sound isolation clips + resilient channel, 2 layers of 13mm gypsum with Green Glue. Thanks!

Trademark Soundproofing answer: Hi Gideon. If possible it is best to put on the noisy side.

How far from the party wall should a second stud wall be built?

Customer question: In trying to avoid the triple leaf affect how far away should I build a second wall from the adjoining office wall. I am next to a bar with the subwoofer on our adjacent wall.

Trademark Soundproofing answer: Hi Karen, As long as you can remove the drywall between the new wall and the old one then any amount of distance will be beneficial. If you cannot remove the drywall in between than we suggest a space of at least 6 inches.

My condo bedroom shares a wall with a loud neighbor - what should I do?

Customer question: Hello, I recently bought a condo, my bedroom wall is shared with my neighbor who happens to be extremely noisy at night hence I have trouble sleeping. I asked the maintanence company of the building if there was any kind of insulation between the walls, they said no. My question is if I add GG and 5/8' drywall to the existing wall that is shared with my neighboor would help to reduce the noise? I can't add the insulation between the walls since this requires hiring a contractor and I'm looking for a diy solution. Thank you.

Trademark Soundproofing answer: It would however adding insulation first would be so much better. You can drill holes in each bay and blow in cellulose insulation then cover with 2nd layer of drywall and Green Glue.

How do I block a neighbor's loud TV through a townhouse party wall?

Customer question: I have one connecting wall,in a townhouse, with an elderly neighbor who plays her TV at a very high volume. The wall appears to be drywall on each side with fiberglass insulation between. My plan is to install 5/8 drywall over the existing drywall using Green Glue and GG Sealant (no clips). My contractor recommends drilling holes in the existing drywall and filling the space between with Great Stuff insulating sealant (which dries hard). Here are my questions please. 1. Is using Great Stuff a bad idea? 2. Is 5/8 drywall ok or should we use Quiet Rock?

Trademark Soundproofing answer: If you have insulation in the walls already, drilling and trying to add some more will not help. 5/8 with Green Glue is fine, no need to use pre damped panels.

Can thin plaster walls in an older condo be soundproofed?

Customer question: Dear Trademark Soundproofing: We live in a 1944-constructed end unit condo w/ plaster walls. Thin--very thin--walls to adjoining unit. Does 'green glue' work w/ plaster? Can we seal over the existing wall w/ green glue & sheetrock? Any possible solutions appreciated! Thank you, Paul Arlington, Virginia

Trademark Soundproofing answer: Hi Paul. You can, provided that the plaster is smooth. It is not the ideal we would much prefer that you remove the wall, properly insulate and use 2 layers of drywall. However we know how difficult it can be to remove these plaster walls........

We hear conversations through the wall of our 1925 twin - what works?

Customer question: I live in a twin that was built in 1925 in Royersford PA. Downstairs we can hear loud conversations from our neighbor and upstairs I can hear coughing. I discovered the party wall is structural terra cotta with plaster applied directly to the block. Could I sound proof with green glue and dry wall? Also would floor joists go all the way across both homes?

Trademark Soundproofing answer: If the plaster is smooth, then yes. Otherwise you would have to sand it down so that the new layer of drywall with Green Glue sits tight. It is possible that the floor joists are shared, we cannot know that without inspecting it.

Why do I hear noise through a concrete block party wall, and how do I treat it?

Customer question: In an existing shared wall which is concrete block structure (cbs), I hear both sound and closing of cabinet doors which are on the neighbor's side. The (cbs) goes all the way into the attic, but I also feel the noise carries over that space as well. My bedroom is next to neighbor's wall and hear all movement when the person closes cabinets, etc. Very frustrated as to what the best solution. Walls and Attic Space?? Please advise. Also can you recommend a contractor in Palm Beach County zip 33418?

Trademark Soundproofing answer: Hi Jean. You need to soundproof the wall and ceiling as well if you have an open attic space above the 2 walls. You are best off with a stud wall and ceiling that has insulation and air space. Thank You.

I can't tear down the wall - can I soundproof over the existing drywall?

Customer question: Dear Trademark Soundproofing, I can't tear down any walls. I have a wall on my side, and there is another wall on neighbor's side (with one cavity (and the studs) in between). I plan to add ONE sheet of quietrock and green glue OVER my wall. I understand the quietrock is to be secured to the studs. My question is: can I add TWO sheets of quietrock OVER my wall? I understand that both quietrock sheets must still be secured to the original studs, and also that one must avoid triple leaf effect (which would be avoided I hope because the two quietrock layers should be flush one over the other over the original wall). Is that possible - is it possible to put two quietrock sheets flush over one existing wall (by securing the two quietrock sheets to the original studs)? (I mean, I am not adding new studs, as I cannot break down into the original wall, etc...) And is that helpful to reduce sound more than one quietrock layer? Thank you very much, Lora

Trademark Soundproofing answer: Yes you can do that and it will help more than 1 layer.

My neighbors' stairs are attached to our shared walls - can I quiet them?

Customer question: I own a townhome, I share walls with my two neighbors, both have stairs on our shared walls. Stairs are very noisy, I hear talking, cubboards shutting, tv, music. What would you suggest doing to these 2 walls that I share with my neighbors ?

Trademark Soundproofing answer: That is a tough one as their stairs are attached to the shared wall. You would need to decouple your wall and treat it. See this how to soundproof a wall article explaining how that is done.

Our party wall continues into a shared attic - is that why sound gets through?

Customer question: I am told there is a 'party wall' which goes all the way up thru the attic between our bedroom and our townhouse neighbor. This sounds like a triple leaf effect. We are disturbed by the neighbor's voice, low frequency talking. What benefit can we expect with GG and 5/8' drywall?

Trademark Soundproofing answer: The Green Glue will have a very big effect on cutting down low frequency sound however you have to treat the wall and the whole in the attic (provided that it goes to the roof and is sealed there). Alternatively you can treat your wall and ceiling.

How do we soundproof a shared office wall?

Customer question: My coworker and I have separate offices, but the shared wall must have a weak connection (the wall sits up against a window frame) because I can hear every move he makes. He can hear every word I say, even if I whisper. Is there something that can be placed in that space (about 4 inches wide from the bottom of the window to the ceiling) to help buffer the sound? Thanks

Trademark Soundproofing answer: hi Deb. If you have a 4 inch wide open gap at the end of the wall then you would need to seal that off first. You can use insulation covered with strips of drywall or plywood and seal with an acoustic caulk. Once that is done you can still have a lot of issues on office walls. See this how to soundproof an office video for more details.