Soundproofing between floors - old house

7 years ago

We own a duplex (one unit upstairs / one downstairs) that was built in the 40s and sound travels readily between the two floors. We you walk around upstairs or play the TV you can easily hear it downstairs. You can even just hear people when they are talking loudly, so obviously not ideal fora two family home.

We are in the process of renovating upstairs now and are planning on adding sound insulation between the floors but worry that won't be enough. The problem is the old hardwood floors are nailed down directly onto the floors joists, i.e. no subfloor. Would it be worth it to take up the old hardwoods and install subfloor and install the old hardwoods on top? Or would it be better to add another layer of drywall down below?

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SJ McCarthy
7 years ago
The easiest solution is to open up the space between the joists (ie. take down the existing ceiling down stairs) and then install a double layer of Roxull Safe N Sound (10 dB) and then add in isolation channels (10-15 dB) and then a layer of 5/8" Acoustic Drywall (18 dB). The total added insulation is roughly 38 - 45 dB. That is MASSIVE. That's equal to 8 - 10 inches of POURED CONCRETE! I kid you not. This should be in the range of $10-$15/sf.

Retroactive acoustic installations are expensive. There is another alternative that might be an option = a layer of mass-loaded vinyl (sheets of 2mm thick "sponge-like" vinyl) glued to the existing ceiling and then another layer of 5/8" Acoustic Drywall added to that layer. This is a faster installation, with a snick less cost (the mass loaded vinyl isn't as cheap as the Roxull) but the added acoustic may be a snick less as well. It depends on the rating (Delta IIC rating) that the vinyl comes with.

The second option usually requires that you have a flat surface to work with (ie. no stucco; no popcorn ceilings down below). If you have a textured ceiling and it tests positive for asbestos, then I would go ahead and add a layer of 5/8" Acoustic drywall and be done with it. Do not disturb the asbestos product (if it is there).

It would pay off to bring in a company that does acoustic installations as part of their advertised services. They will save you MONTHS of investigation as well as THOUSANDS of dollars of "would have done it had I known it at the time" kind of kicking yourselves.

As a former cork flooring sales person, I helped people achieve a quiet environment on a DAILY basis. Believe me when I say this, you don't know what you don't know. Too many homeowners go into an acoustic retrofit with a basic idea only to come out on the other end having spent too much money on "sales pitches" and not enough acoustic insulation to make the project viable. In other words they spent WAY too much money for the small amount of benefit they created.

Please sit down with some professionals who deal with acoustic installations on a weekly basis. They will have TONS of ideas/options and budget price points from which to choose.

Budget should be around $10/sf. It can be done for $7/sf...or it can be done for $20/sf. It all depends on how bad things are and how much you WANT to add.
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