Soundproofing Floor Between Upstairs / Downstairs Units

[Spencer Holland]

I recently purchased a home built in 1964 in a great location in Denver (LoHi). We have a separate entrance that allows us to turn our 4 bedroom into two 2 bedrooms. We have just begun Airbnbing out the lower unit and my largest concern is the noise from walking upstairs. This isn't a huge deal for Airbnb, but I'm thinking long-term about a solution for when I move out and rent out these 2 units. This is a higher-rent area, so those tenants would have higher expectations. I'm willing to make a decent-sized investment here, but how can I stop the noise that comes from the hardwood floors upstairs shaking when we walk on them? The bathroom and kitchen also both have tile which is about 1/3 of the upstairs

[Bill S.]

@Spencer Holland several of the suggestions can be done for under $10k for 500 sqft. You can easily add a 2nd layer of drywall. I have done a LOT of research on this issue and have done a number of the "fixes". My experience says that this cuts down on the magnitude of the sound but you still hear it.

The very best result was from taking up the upstairs flooring, installing mass dampened vinyl then a mat of 5/8" plywood (2 layers layed at 45 deg angle with green glue between the layers) and then a new hardwood floor, along with blown in cellulose between the floor joists and then j-channel on the existing basement drywall ceiling with a 2nd layer of drywall in the basement. About all you hear in the basement unit is a chair being drug across the floor. Not cheap but it works. I did this because the hardwood floor in the upper unit was trashed and I needed a new floor so I wouldn't recommend the mass dampened vinyl unless you were doing a new floor anyway.

The last item is the heating system. If you have shared ductwork, you are wasting your time and money doing sound proofing. Ideally if you have ducts, you need two completely separate systems. The shared ducting carries the sound between the floors and there is no way around it without creating separate systems. The metal duct even tends to amplify some noise.