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Q. I’m doing a gut renovation. While I'm at it, how do I soundproof the walls, floors and ceilings?
A. Soundproofing is very, very tough. Tough enough that for the purposes of answering your question, we’re going to refer to "sound isolation," which is the process of reducing, by some degree, sound transfer from one place or structure or material to another. "Soundproofing," meanwhile, implies a complete elimination of unwanted sound and can be very difficult to achieve in most residential renovations or upgrades. It's important to keep your expectations realistic.
A quick background on sound transfer
Sound energy can move through air—and even the tiniest amount of air can travel in any space—as well as through solids. But it moves through these mediums at different speeds and to different degrees.
Thus, you might stop sound from moving through a crack in a door, but the energy might go through the "solid" doorframe. Sound is also made up of a range of frequencies, from the "lows" to the "highs," and different methods and materials are sometimes appropriate for higher- and lower-pitched sound.
Cut down on building noise
The first thing you’ll want to consider is just how much noise you’re dealing with and where it’s coming from. Do you want to reduce the sound from a playground across the street? Or do you live directly above a salsa club that’s open 'til 3 a.m.? These two problems require drastically different approaches.
If it's the salsa club, we’d expect much lower frequencies and a much louder source (the club’s amplified sound system).
The most basic sound isolation improvement will be adding layers of materials. If you’re redoing the walls (which you will be with a gut reno), add a few extra layers of drywall. If you’re taking floors back to the joists, add two or three layers of plywood as a base floor, instead of just one, and then the finished flooring on top.
When you're putting in the drywall or plywood, fill in the gaps where sound can sneak in.
"It’s a matter of finding and sealing every small hole, open seam, and open area around pipes or wiring. Use caulk everywhere and seal these up airtight,” says Mark Genfan, from Acoustic Spaces, an Austin-based firm that designs recording studios, theaters and performance spaces.
But the best solution is to "de-couple," creating a space between the walls or floors, provided you protect the integrity of the structure. For example, instead of building a heavy-duty wall with four layers of drywall, you'd reduce the noise if you built two parallel walls separated by an "air gap."
"Isolating sound that is carried through solid materials like the foundation, walls, ceiling and floor requires truly 'de-coupling' one solid element from another, which means breaking an actual physical connection between two materials," explains Genfan.
Muffle outside noise
In the case of sound coming from the playground, you'll have a tougher time bringing the volume down. Windows and doors are especially difficult to sound isolate, because they open and close--so it’s nearly impossible to get a good air seal. Also, many residential doors are hollow, and glass is not very dense, meaning sound passes through them more easily than a typical wall.
"If you add solid core doors and specialty windows with thicker glass and very tight seals, it can make a big difference,” says Genfan.
Granted, you can expect to double your costs if you go with these materials. Sometimes the best way to gauge the difference they make is to visit the home of someone who's used them.
Products on the market
Some materials are available that can help with noise, but you’ll need a pro to handle them.
"We use Green Glue a lot," says Genfan, referring to the noiseproofing sealant. "We’ve tested it extensively, and feel it’s a cost-effective upgrade. ... We also use common, off-the-shelf drywall, as it’s just as good as the more expensive varieties, but we upgrade to ‘professional grade’ door seals, instead of ‘residential quality.’”
Other products like Quiet Rock, a drywall alternative, work well but cost a lot more.
Fraser Patterson is a former general contractor and the founder of Bolster, a NYC-based company that guarantees the price and outcome of home improvement projects with a first-of-its-kind Home Improvement Project Bond. For more information, visit http://www.getbolster.com. To ask a renovation question, click here.