Soundproof your garage or workshop

Mass appeal

Reducing noise begins with eliminating all of the cracks leading out of your workshop, and increasing the STC of your walls and ceilings–and for that matter, doors and windows (we’ll return to these portals later on). If your shop is sheltered by 1/2″ drywall, consider replacing it with 5/8″ drywall. The increased mass helps to block sound and has the added benefits of increased fire protection and durability (you won’t rip a hole when you accidentally ram a piece of lumber against it). “I also have an internal wall with a special treatment,” says Maxwell, referring to his basement shop. “Before applying the drywall, I fastened 1/2″ fibreboard to both sides of the wall frame. This material, combined with the drywall, does a pretty good job of stopping sound.”

Before installing drywall, you need to stuff the cavities with sound-dampening insulation. Many people think regular insulation works fine and, for most practical purposes, it works fairly well.

“My [stand-alone] shop is right between a bunch of old houses, so when I had it built, noise was a consideration because I didn’t want to irritate my neighbours,” says Konrad Sauer, a woodworker in Kitchener, Ont. “We insulated beyond code and installed highly efficient windows and doors, and so far there have been no complaints. I have a friend who’s a professional drummer, and he couldn’t believe how quiet it is outside my shop, even when I was blaring loud music.”

While regular insulation does hamper sound, you can’t just stuff your cavities with as much insulation as possible and hope for quiet times. “Interior walls are typically 2×4, so cramming R20 batts, which are 6″ thick, into a 2×4 space isn’t going to work,” says Goyda. “If you compress the batt, you lose the acoustical value because it’s the air pockets in fibreglass or rock-wool insulation that trap sound.”

It works like this: when the vibrations try to work through the batts, the vibrations travel along fibres, and the fibres are criss-crossed and mismatched, so the energy keeps changing direction. As it does this, it turns into another form of energy–heat–and is trapped in the air pockets. “That’s how insulation absorbs sound, by absorbing heat,” says Goyda.

Acoustical batting, such as QuietZone, a fibreglass insulation made by Owens-Corning, and Safe ‘n’ Sound, a rock-wool insulation made by Roxul, are available in most hardware stores and retail for about the same cost as standard insulation. Neither carry R-ratings, but since you’ll be using the batting for interior walls, it doesn’t really matter. Plus, with noise, it’s thickness, not R-ratings, that count.

Safe ‘n’ Sound, which is made from basalt rock and recycled steel slag, has a higher fire rating than fibreglass insulation. Because of its density, you can make intricate cuts to fit it around electrical outlets and wiring. “Instead of using a utility knife, use a serrated bread knife,” says Kirby Williams, product application and development manager at Roxul in Milton, Ont. “Instead of pulling it behind wiring, like you would with fibreglass, you score the back, open it up and fold it back over the wire.”

Williams believes the key acoustical quality is density: “Density improves the reduction of lower-frequency sounds such as the noise from power tools.”