Soundproofing a Converted Garage From the Main House in Port Moody

Installing proper soundproofing between a converted garage and the main house in Port Moody typically costs $3,000 to $10,000, with the range reflecting whether you are doing basic improvement or targeting near-complete sound isolation. The shared wall between the garage and the house is the critical barrier, and addressing it effectively requires understanding how sound travels and applying multiple strategies rather than relying on any single product.

Sound transmission between spaces is measured using the Sound Transmission Class (STC) rating. A standard interior wall with single 2x4 framing and one layer of drywall on each side achieves an STC of approximately 33 to 35 — enough that normal conversation is audible through the wall, and loud music or television is clearly heard. For comfortable living conditions where the converted garage serves as a bedroom, office, or rental suite, you want an STC of at least 50 to 55, which reduces sound to the point where loud speech is barely audible and music is essentially inaudible under normal conditions.

The good news is that a garage conversion gives you an ideal opportunity to address soundproofing because you are already opening up the shared wall (or building new walls) as part of the conversion work. Retrofitting soundproofing into an existing finished wall is far more expensive and disruptive, so tackling it during the conversion is both practical and cost-effective.

Here are the primary soundproofing strategies and their costs for a typical shared wall between a converted garage and the main house (assume approximately 4 to 6 metres of wall length, standard 2.4-metre height):

Insulation in the wall cavity is the foundation of any soundproofing approach. If the shared wall is currently uninsulated (common for garage-to-house walls in Port Moody homes), filling the cavity with mineral wool (stone wool) insulation such as Roxul Safe'n'Sound provides substantial improvement. Mineral wool is denser than fibreglass batt and performs significantly better for sound attenuation. Material cost is approximately $2 to $3 per square foot, and installation during a garage conversion adds minimal labour cost because you are already working on the walls. Total for insulating the shared wall: $300 to $600. This alone can improve the wall's STC from approximately 33 to about 39 to 42.

Adding mass with additional drywall layers is one of the most effective and affordable upgrades. Sound transmission decreases as wall mass increases. Adding a second layer of 5/8-inch drywall to the garage side of the shared wall (on top of the existing single layer) increases mass and improves STC by approximately 3 to 5 points. Using mass-loaded vinyl (MLV) — a dense, flexible sheet material — sandwiched between the two drywall layers adds further improvement. The combination of MLV plus a second drywall layer can boost the wall's STC by 8 to 12 points. Materials and installation for double drywall with MLV on the shared wall run approximately $1,200 to $2,500.

Resilient channel or sound isolation clips provide the most dramatic improvement by decoupling the drywall from the framing, which interrupts the direct path that sound vibrations travel through solid materials. Resilient channel is a thin metal channel that attaches to the studs, and the drywall screws to the channel rather than directly to the studs. This creates a small air gap and a flexible connection that dramatically reduces sound transmission through the structure. Sound isolation clips (such as the WhisperClip or similar products) with hat channel provide even better decoupling performance. Adding resilient channel or clips to the garage side of the shared wall, combined with insulation and double drywall, can achieve an STC of 52 to 58 — well into the comfortable range. Cost for resilient channel or clips plus installation: $800 to $1,800 for the shared wall.

Sealing all gaps and penetrations is critical and often overlooked. Sound travels through any opening — electrical outlets, gaps around pipes, spaces where the wall meets the floor or ceiling, and cracks in the drywall. Acoustical sealant (a permanently flexible caulk designed for sound control) applied at all perimeter joints, around outlet boxes, and at any penetrations costs only $100 to $300 in materials and labour but can make a noticeable difference. Using putty pads — fire-rated acoustical putty wrapped around electrical boxes — prevents sound from leaking through outlet openings, which are one of the weakest points in any wall assembly.

The door between the converted garage and the house is typically the weakest link in the sound barrier. A standard hollow-core interior door has an STC of only about 15 to 20 — far below any wall assembly. Replacing it with a solid-core door (STC approximately 30 to 35) with proper weatherstripping and a door sweep dramatically improves the situation. A solid-core door with acoustic seals costs $400 to $900 installed. For maximum sound isolation, a purpose-built acoustic door with STC ratings of 45 to 55 is available but expensive at $1,500 to $3,000 installed.

For a comprehensive soundproofing package on the shared wall and door in a Port Moody garage conversion — mineral wool insulation, double drywall with MLV, resilient channel or isolation clips, acoustical sealant at all joints and penetrations, and a solid-core door with acoustic seals — expect a total investment of $4,000 to $8,000. This achieves an overall wall-and-door STC in the range of 48 to 55, which provides comfortable sound separation for virtually any use including a bedroom or music room.

If you also want to address sound transmission through the ceiling (relevant if the converted garage is below a bedroom), add another $2,000 to $4,000 for a similar treatment on the ceiling assembly — resilient channel, insulation, and double drywall.

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