Thin walls and soundproofing

12 Replies

When you’re living in a multifamily and are able to hear people next door or downstairs, people will say it’s because the “walls are thin.” Is this literally due to having thin drywall? Is there not good insulation? No insulation?

How do you improve the soundproofing between units side by side and top/bottom?

I’ve read using 5/8” drywall can help between walls and on ceilings. Also using acoustic insulation and resilient channels on the ceiling. Have y’all found that these measures work?

Really good question. I am not sure, but what I can say is traditionally those complaints come from stick built MFR's. I don't seem to have this issue with Concrete built, but I would imagine it would be as easy as installing sound reducing drywall, really good insulation, and sound deadning floor underlayment?

Sorry I can't be of more help, but I can't imagine it's something complicated.

Hi @Taylor D. Jenkins

I had a similar issue with a unit of mine, where there is a one bedroom lower unit and 3 bedroom upper unit. I ended up ripping out the ceilings of the 1 bedroom when it was unoccupied to finally "fix" the issue.

I went with Roxul Safe n Sound insulation, 2 layers of quiet rock (supposedly like 8 pieces of normal drywall compressed) held together with green glue. Additionally I mounted the quiet rock on clips so that it wasn't directly touching the floor above and ran some resilient channels.

I probably went overkill, but I just never wanted to deal with it again so I figured I mine as well do it right the first time.

Is it perfect, no, but it's 90%+ better. You can't hear people talking but you still do get a little impact noise from people walking loudly. Impact noise is the hardest to get rid of, but it's at a point where tenants are no longer complaining.


If you have additional questions, don't hesitate to send me a DM.

Thicker drywall itself might not do the job. The sound could be carried in HVAC registers, cracks around electric boxes, under and around doors and even through the ceiling. Make sure all penetration points are sealed, check the registers, weatherstrip doors - then see if that helps. I would then see if I could put a spray-insulation with soundproofing qualities in the walls between the studs (ask an experienced handyman or contractor). If the floors are hard floors - carpet also helps with sound-dampening. Good luck!

Great question. The answer is, like most things, yes and no.

Yes, thicker drywall can help, which is why quite rock works, but not why you may think. The sound waves are being transferred mainly through the connection points in the walls so the 2x4's. Increasing the thickness of the drywall means there are at least two areas where the density disrupts the waves a bit more than normal. quite rock qorks because the material makes it harder for the wave to transfer not simply because it is thicker. This is why the solution mentioned above (quite rock clips) works so well. Rather than have the sound transfer along a 1.5in by 8ft piece of uninterrupted lumber you are creating a sound gap where the wave must "skip" through. This is also why you can still hear footsteps but not talking. With speech, the sound wave is created at the vocal cord and then transfer through the air to the drywall lumber whereas footstep noise is created at the connection of the floor. The vibration is created at that point and therefore the vibration is transferred much more efficiently. Keep in mind also that sound from your voice can also transfer through the floor connection at the base of your walls. Another reason insulation has a minimum effect.

Insulating walls will have some effect as waves definitely do transfer through those spaces but again the reason this only cuts down on a small percentage of your sound is because of the reasons above.

There are many ways to cut down on this but one method I've found to be particularly cost-efficient is to have a min 1/2in gap between a double 2x4 insulated wall where the studs are staggered 16in on center ensuring that at no point do the two walls touch. If possible make sure to connect the wall framing to the floor framing before installing any floor sheathing (osb) as it acts as an interrupter for the floor sound transfer. This wall method sacrifices space (Your shared wall will be about 8.5" thick) but allows you to eliminate the costly systems mentioned above. One way to do this on the floor is to apply a poured down underlayment (basically concrete) on the floor above and clips for the drywall on the ceiling below making sure to insulate.

There are many other ways to achieve this but the strategy I just outlined has been the most cost-effective way to achieve that. Again, there are other ways and you'll have to weigh the cost/benefit of each. Good luck!

Are your tenants complaining? Are you in a rehab phase that would allow you to "double-dip" on this kind of solution?

I had a similar issue on a building where the previous contractor was supposed to insulate the dismissing wall. We didn't realize he had failed to do so until the tenants complained they could talk to each other through the walls. We were able to have a company come in and insulate the walls by cutting small holes into each "bay" of the wall and blow insulation into the cavities this was about $1,700 for our two-story building. Adding drywall w/ green glue, while would have provided more noise cancelation, was going to cost us close to $7,000 as it would have required not only drywall labor but also, paint, baseboards, and touch-up work. So far so good on the insulation... here's to hoping it stays that way.

@Taylor D. Jenkins

Kurt offers a great explanation, and hits the major points.  Anywhere there is a physical connection or way for vibrations in air to continue moving, you will get noise.  I am guessing you are just wanting muffled noise that generally won't create complaints, which often times putting up a second layer of drywall will be your easiest and cheapest route, assuming you aren't doing a full gut.  

If the walls are gutted to studs, at least on one side, adding rockwool and second layer of drywall will stop most sound transfers.  We have this in the wall between our bedroom and laundry room, and works well enough to not keep us up with washer or dryer running at night.  

If you are talking about sounds of people walking in second floor unit, that will be much more challenging, since wood has a natural bounce to it, and that would start to become a structural issue, as well as sound deadening.

Originally posted by @Kurt Snyder :

Are your tenants complaining? Are you in a rehab phase that would allow you to "double-dip" on this kind of solution?

I had a similar issue on a building where the previous contractor was supposed to insulate the dismissing wall. We didn't realize he had failed to do so until the tenants complained they could talk to each other through the walls. We were able to have a company come in and insulate the walls by cutting small holes into each "bay" of the wall and blow insulation into the cavities this was about $1,700 for our two-story building. Adding drywall w/ green glue, while would have provided more noise cancelation, was going to cost us close to $7,000 as it would have required not only drywall labor but also, paint, baseboards, and touch-up work. So far so good on the insulation... here's to hoping it stays that way.

 No complaints right now. Just planning for the future. What you did seems like a good alternate plan to add to the toolbox

Originally posted by @Evan Polaski :

@Taylor D. Jenkins

Kurt offers a great explanation, and hits the major points.  Anywhere there is a physical connection or way for vibrations in air to continue moving, you will get noise.  I am guessing you are just wanting muffled noise that generally won't create complaints, which often times putting up a second layer of drywall will be your easiest and cheapest route, assuming you aren't doing a full gut.  

If the walls are gutted to studs, at least on one side, adding rockwool and second layer of drywall will stop most sound transfers.  We have this in the wall between our bedroom and laundry room, and works well enough to not keep us up with washer or dryer running at night.  

If you are talking about sounds of people walking in second floor unit, that will be much more challenging, since wood has a natural bounce to it, and that would start to become a structural issue, as well as sound deadening.

I was more referring to lessening the sounds of people walking upstairs. I've heard that it's difficult to help that as you've mentioned. Being able to at least eliminate or almost eliminate verbal sounds, music, etc would at least be worth something though

 

In some of our buildings in Cleveland Heights when it comes to up and down stairs issues, many of the units have wood floors or tiles.  There is a section in the lease that the floors need to be covered 70%.  Meaning put down rugs or other type things to help with noise if an issue.  As for walls, it is true that unless you have access to the inner wall, it does become hard to muffle sound in between them.  Inbetween tenants if you have issues you can put insulation in between inner walls where you may not normally put insulaltion and that does make a huge difference in sound levels. In one of my offices I did that and it does help out a lot to keep sound in the office and any sound out of it out.  Double layering the drywall may or may not help depending on the structure of the place for a cheap fix.  It will definatly help some if done on both sides of an inner wall of both apartments.  The inside of the wall will be an issue if it is the real issue.  

Sometimes though, some tenants are more bothered by noises than others. So also if it has not been a problem before or yet, something for white noise for the tenant so they are not bothered by the other tenants may also be a good solution, assuming the other tenants also are not making noise out the ordinary.  I hope you found some of that helpful Taylor.