By Bob Gatton
At the 2008 International Builders' Show in Orlando, a product at the Knight Celotex booth caught my eye: SoundStop is a 1/2" sound-deadening fiberboard that is installed under the drywall in walls and ceilings. It's also a green product, made from either recovered hardwood or sugar-cane fibers, and it counts toward LEED certification.
Why would you want to use a sound-deadening product in your homes? There are a couple of primary reasons:
- Keeping exterior noise out of the home. Houses are being built on smaller lots; they are closer and closer to their neighbors. And many new homes are also being built closer to roads and other sources of noise.
- Keeping interior noise in the home or in part of the home. Media rooms, home theaters and music studios are becoming more common. Or maybe you just want to shield some of the rooms in a home from noise in other areas.
Celotex recommends installing the sheets of SoundStop vertically on the wall with the drywall attached horizontally.
I have not tested this product, but the company has had independent testing on its effectiveness. The measurement for this is the sound transmission class(STC). The higher the STC number, the better the product is at blocking sound. A single sheet of SoundStop has an STC of 23, but a wall consisting of 5/8" drywall, a sheet of SoundStop, then 2x4 wood studs, another sheet of SoundStop and finally a second sheet of 5/8" drywall can deliver an STC of 50.
Check out the interesting demo on the Celotex website, where you can listen to the same sound at STC levels between 46 and 60. You'll see (or rather, hear) that while an STC rating of 50 is not soundproof, the reduction in volume is very significant. Different wall configurations can deliver higher or lower levels of noise blocking, too.
A few things to keep in mind:
- You cannot lay flooring directly over SoundStop; it is not a structural product. You'll need to install 1x3 wood sleepers and a 5/8" plywood underlayment on top of the SoundStop and under the carpet. Celotex makes an underlayment product, too.
- SoundStop does not reduce the one-hour wall system fire rating.
- SoundStop can be installed over existing drywall, with a second layer of drywall then installed over the SoundStop.
- If you use SoundStop on the walls, ceiling and floors, sound can still be transmitted via the doors, windows and HVAC ducts. If you want soundproofing to be as complete as possible, check out the articles and videos about acoustic framing, acoustic windows and quiet HVAC systems.
SoundStop is available in 1/2" x 4' sheets either 8 or 9 feet long. The 4' x 8' sheets cost about $10 each — a pretty cost-efficient upgrade if you're building near a busy highway or airport.
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