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Install floating floor over plywood with neighbor below

15 years ago

I'm building a multi-family structure where a small portion of the building overlaps another unit in the same structure - so one living unit over another. The area is small (about 300 sq ft on two separate units) but I want to install hardwood floors in the bedrooms and I understand hardwood does a great job of passing impact noise to occupants below. So I'm going to try install hardwood AND isolate all above/below noise transmission.

I have 12" joists (TJI) running 16" OC. I heard floating floors are the best choice as you can place an underlayment (e.g. 1/8" thick rubber mat or recycled material) below the hardwood. Question is if I use nail down hardwood flooring, can this material still be used? I still haven't installed the plywood subfloor either and I read on some websites that placing an acoustic tape over the joists (between the joists and the subfloor) can help reduce some impact noise to below. I usually use screw and glue to adhere the plywood subfloor to joists but using this tape would mean no glue. My concern is that not using glue could result in the subfloor "moving" and causing future squeaking in flooring. The guy selling the tape said the tape does the opposite - and actually helps to reduce squeeking in floors. I find that a bit hard to believe. But I'm no professional.

If anyone can chime in as to what's the best way to prevent noise passing through to occupants below when using a hardwood floor, I'd really appreciate it. Note that resilient channels below are not an option because I need to maintain my 8' ceiling heights. I do plan on going with the obvious - like insulation in joists and perhaps even using the tape between the bottom joist and drywall (ceiling).

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