Soundproofing near you

Airborne noise starts in the air, as voices, music, a television or a barking dog. It sets walls and floors vibrating slightly, and they pass the sound on to the other side. Impact noise starts when something strikes the structure directly: footsteps, dropped objects, chairs dragged across a floor, a door slammed in its frame. The two call for different fixes, and many complaints involve both.

Most soundproofing assemblies combine several of these principles, because each one handles part of the problem. None of them is a single product you can add to a wall and forget.

Flanking spoils many projects: sound goes around the treated wall through the floor, the ceiling, a continuous joist, a duct or back-to-back outlets. Before choosing what to build, a good contractor traces the whole path from the noise source to your ear.

Assemblies are compared with two ratings. The Sound Transmission Class, or STC, describes how well a wall or floor blocks airborne sound in a laboratory test, and the Impact Insulation Class, or IIC, describes how well a floor and ceiling assembly resists impact noise such as footsteps. For both, a higher number means better performance.

Laboratory ratings describe an assembly built perfectly, with no side paths. In a real building, outlets, ducts, gaps and the surrounding structure lower what you actually get. That is the idea behind apparent ratings, which account for those paths: when the Régie du bâtiment du Québec updated the Construction Code, it aimed to improve soundproofing in dwellings, notably by introducing an apparent sound transmission index. When a contractor quotes a rating, ask whether it comes from a tested assembly that matches what will be built, and be wary of any promise of a specific number in your home.

Walls and floors between dwelling units have to meet building code requirements for both sound and fire. If your project creates a new unit, such as a basement apartment, or changes a separation between units, ask your municipality about permits before work starts.

Fire separations must stay intact. A wall or ceiling between units, or between a house and an attached garage, is built to slow the spread of fire and smoke, and soundproofing must not weaken it: fire-rated gypsum that is cut is restored to the same rating, penetrations are sealed with approved firestop products, and a tested assembly is rebuilt as tested rather than improvised. Ask the contractor to state in writing how the fire rating will be maintained.

In a condo, the walls, floors and ceilings between units are often common portions or governed by the building's rules, and many buildings set requirements for flooring underlay. Before any work, read the declaration of co-ownership or the bylaws and ask the condo board what is allowed and what approvals you need.

Soundproofing reduces noise; it rarely eliminates it. A well-built retrofit can make a neighbour's conversation much harder to make out, but deep bass, heavy footsteps on a light wood-frame floor and noise that travels through the structure are stubborn. The more of the path you can treat, including the floor above or the neighbour's side, the better the result.