What Can I do about sound in a duplex with thin walls?

Question

Hello - I have a side-by-side duplex that i'm converting into an STR.  I noticed that the walls are somewhat thin and when I'm sitting in one of the units I can hear some noises from the other unit.  Is this a problem?  Should I install some sound dampening panels on the walls to reduce the noises from the other unit?   Help!

Michael Baum · Answer

Hey @Marc Shin, what you can do is add a second layer of drywall over the first. This will keep you from having to tear it all out and making a mess. A good drywall guy can hang and finish it in less than a day easily.

But what you need to do is put a bunch of Green Glue between the sheets.

When hanging, the contractor will spread the Green Glue on the new panels in a random pattern with a caulking gun. Then attach as per normal.

Green Glue is a product that is designed to reduce the transference of sound between rooms. It is usually used in conjunction with decoupling clips and the like for listening rooms, audio recording rooms and home theaters.

It is very effective in and of itself so it is something that can be done reasonably cheap without taking a ton of time.

https://www.greengluecompany.com/

John Underwood · Answer

Yes it's a huge problem.

You should fix this correctly now.

Open the walls and put in proper sound reducing insulation.

Mike Grudzien · Answer

Marc,If you can hear noises, Guests can hear noises.  Guests provide revenue and guest provide Reviews.  Connect the dots and get those panels.  Perhaps on both sides.My 2 cents,Mike

Alberto Rivera · Answer

@Marc Shin,

Soundproofing is definitely something worth tackling for a short-term rental—it’ll keep your guests happy and help you avoid complaints. Here’s my recommendation to get it under control:

For a quick fix, start by sealing up any gaps using acoustic caulk around outlets, baseboards, or other small openings. This will help stop sound from sneaking through. You can also throw up some sound-dampening panels on the shared wall. They’re easy to install and, while not perfect, they’ll make a noticeable difference. Lastly, check any shared doors or gaps and add door sweeps or weatherstripping to block sound from traveling between the units.

If you’re looking for a long-term fix, go for a more robust approach. Adding mass to the walls works wonders—attach Mass Loaded Vinyl (MLV) to the shared wall, then cover it with a layer of 5/8” drywall using Green Glue soundproofing compound for extra noise-blocking power. If you can access the wall cavity, adding rock wool (mineral wool) insulation will make a big impact by reducing vibrations and sound transfer.

These solutions can make a huge difference, and the long-term option will really help set your STR up for success. Let me know if you’d like specific product suggestions—I’d be happy to help!

Best,

Alberto Rivera

Brian Dance · Answer

@Marc Shin,

Totally agree with what Alberto stated above. I put in two layers of rockwool + 5/8" drywall between my basement and main level, and was so glad I did it. It's a bit expensive, but do it once and forget about it.

The technical term is Sound Transmission Class. This Wikipedia page gives different wall types and how well they block sound.

https://en.wikipedia.org/wiki/Sound_transmission_class#:~:text=The%20STC%20or%20sound%20transmission,insulation%20than%20a%20lower%20number.

Bruce Woodruff · Answer

This ^^^^^^They also make sound deadening drywall, like QuietRock...

Morgan Leiviska · Answer

There is a soundproofing drywall quietcrete i think, as well as insulation panels, sound dampening paint, and green glue is a compound that you can roll on as well. likely there is no insulation or it wasnt installed well. air gaps equal noise.  if it were me, I would probably take the drywall down from one side, make sure there is good insulation installed properly with no air gaps, install the quietcrete and see how it is. then if still bad, roll on some green glue and another thin sheet of drywall.

Bruce Woodruff · Answer

Stay there one night and test it yourself. IF it is a real problem, then yes, fix it.

I would build a fir-in wall out of 2x2s and insulate it heavily (Rockwool comes to mind https://www.rockwool.com/north-america/) There is also drywall that is made for this.

Andrew Steffens · Answer

Yes, if it is that bad you will have constant headaches.  Definitely do what it takes to add some sound proofing.  Does not need to be perfectly soundproof but if it as bad as you allude to then you need to deal with it as soon as possible.

Shannon Strickland · Answer

I previously researched solutions for a similar sound problem where I could not open the walls, but I still have not solved the problem. A solution company that intrigues me is Acoustimac.

What Can I do about sound in a duplex with thin walls?

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