Sound proofing units

[Amy A.]

I recently purchased a 12 unit building which I would like to take from class C+ to class B+. There are two 3 bedroom units on the second floor and the rest are 2 bedrooms.  I was just given notice (for November, not great timing) that the two units below the 3 bedroom units are moving out.  The noisy kids upstairs are a factor.  The 3 bedroom units will probably always have kids, so this will continue to increase my turnover.  I am considering sound-proofing the lower units by adding a product called QuietRock to the ceiling and shared walls.  Has anybody used this or is there a less expensive product you know of?  The ceilings need work anyway.

[Roy N.]

@Amy A. 

There are a variety of products out there for sound proofing ranging from practical to what you would use to build a recording studio ;-)

QuietRock and other products like it are a double layer of (typically 1/2") sheetrock with a baffle between them designed to dissipate sound waves.  Are you planning to install this over the existing ceiling or to replace the drywall which is there now?

Your existing ceilings between units should be 5/8" fire rated drywall suspended from resiliant channel to meet modern fire code.  If your ceilings are not already this configuration and you are planning to pull them down, then you may be able to sound proof sufficiently while fire rating your ceiling.   

When fire rating common walls and ceilings, we fill the cavity with a layer (or two) of Roxul Safe-n-Sound (or an equivalent dense stone/rockwool), sometimes in combination with the denser Roxul Comfortboard {for additional firestop}.  Over that we strap the wall/ceiling with resilient channel - the resilient channel both provides better hold for the sheet rock in the event of a fire {i.e. ceiling stays up longer} and, by suspending the drywall off the floor joist reduces the low frequency sounds/vibrations from the floor above {i.e. running little kids or pets}.  Finally the 5/8" fire rated drywall is installed.

The 5/8" fire rated drywall itself is not as good a sound baffle as the QuietRock, or using baffle plates on the ceiling, but when combined with the rock wool and resilient channel it comes close while meeting the fire stop requirements necessary in a multi-unit building.

You could use the rock wool, resilient channel, and then hang the QuietRock (which is 1-hour Fire-X rated) to achieve greater noise reduction.  {Note: PABCO Gypsum claim QuietRock can be attached directly to the studs/joists without resilient channel.  I would first verify with your local building inspector or fire marshall that it still meets fire code when installed in this manner}.