Soundproofing under wood flooring...

I'm thinking about having wood floors installed in a 1000 square foot condo. This unit is second (top) floor, and is an end unit. I'd like to know if there is any sort of surface prep or underlayment that could go on the subfloor prior to having the wood flooring installed, that would significantly soundproof the unit so that the tenant below won't hear me playing Dead at 3AM.

 

Yes, though I can't personally speak for its effectiveness. A contractor told me if thicker rubber sheets are used the floor can start to feel a bit wobbly. I've also heard of a sound-absorbing mastic so you might look into that.

 

If your neighbors can hear you while you are playing Dead, you should consider signing up for some acting lessons.

-Bill

 

Doesn't your HOW have rules/guidelines that address this? Mine is very specific about what's required if one wants to remove carpet in favor of hard wood floors.

 

To pick up on this point, I bought an apartment in The Netherlands when I lived there, and a traditional hardware floor was not allowed according to the rules due to contact noise. Since I had an apartment on the first floor, had commercial space below me, and a much thicker concrete floor between me and the commercial space, I actually put in a traditional hardwood floor (I was never home during office hours, and would have been bare foot if I was). The rules, though, called for a 'floating' hardware floor. I imagine you will have to put in something similar. It has various decoupling layers built in, and the wood is not nailed into the sub-floor, as I recall.

I doubt that what you are planning will do much to dampen sound transmission through the main structure of the building (at least that is my experience of several apartments over the years). You will have to find a way of preventing the sound energy from getting into ducts, etc. that can transmit it. The decoupling built into the floating floor may do the trick, but it may not. You won't know until it is in, unfortunately.

 

^ Great advice, Black Elk.

I got into this subject when I designed my last stereo store. I wanted customers to be able to crank it in a sound room and not have it bleed through the entire store. In previous stores, one system playing loud could shut down the entire store. Nobody else could do any listening.

Here were the basic ground rules for sound proofing my stereo store:

• Nothing beats an air space for sound proofing. In recording studios, for example, to sound proof a room it's common to build a wall, leave an air space, and then build a second wall. You'll even have two doors back to back, one for each wall, since nothing should connect the two rooms together. This wasn't a practical solution for me with my stereo store and I doubt it will be for you. I didn't do this.
• You don't want anything to run between yours and your neighbor's unit, like a heating duct, cold air return or utility chase. Sound will travel through those areas and everything else you do will be in vain.
• Enclose your listening room. Not only can sound be transmitted through the floor but if you have an open ceiling, or sound leaking into an adjacent room, that sound might find a pathway down to your neighbor's place. Your room has to become a tightly sealed box. In my case this meant I didn't use dropped ceilings in my sound rooms.
• Cross bracing is essential. We used horizontal cross bracing between the studs in the walls and joists in the ceilings of my stereo store. Stiffening the walls and ceilings up helps a lot. In fact, most of my sound proofing came from this, along with using real ceilings in the sound rooms. In your case, you'd want to use cross bracing in the floor, across the joists (I was on a concrete slab for the floor).
• The least effective solution is stuff in the walls and floors. Insulation doesn't make much of a difference at all.

Even with all this, you will only attenuate the sound you transmit. You won't kill it. You could lower levels 10-15 dB over not having any soundproofing at all. That might be enough to save you if the neighbor's living room will be below yours and their bedroom is well away, but you'll never kill the sound you transmit completely. The closest to a magic bullet is the double wall, or in your case, double floor, solution, but that might be as impractical for you as it was for me. Something similar to the floating floor in Black Elk's post would be a better solution but it would only be part of the answer. You have to do everything else right, too, for sound not to find another pathway into your neighbor's condo.

 

I built a soundproof room on the second floor of my house to play drums any time of night. I spared no expense. And, it works. However, it attenuates the sound, it doesn't eliminate it. And, if you want to put something under your flooring to stop the transmission of sound to your neighbors, forget it. Nothing you do will work. The only thing that will stop your neighbors from hearing loud sound is if your living space is physically disconnected from the structure of your neighbor's building. You can put a layer of mass loaded vinyl (MLV) under your new floor but it will be relatively expensive and then you may have to convince yourself its having any effect. When I built my studio, I floated a new, 5 layer thick floor on top of the existing floor, the room is air tight, walls and ceiling are 5 layers thick of drywall/MLV and are decoupled from the studs, ventilation is exclusive, etc., so I know from experience. The problem in your situation is you're sharing the same structure. No amount of mass or damping will stop sound from being heard by your neighbors.

 

Some CC&R's have rules against installing wood (only) floors on the 2nd floor, especially if the previous floor was carpeted. Read 'em carefully.