How much does it cost to soundproof shared walls in a Toronto duplex using double drywall and resilient channel?

Soundproofing a shared wall in a Toronto duplex using resilient channel and double drywall typically costs $5.00 to $10.00 per square foot, with a typical shared wall of 150 to 300 square feet running $1,500 to $3,000 per side — or $3,000 to $6,000 if both sides are done. Adding acoustic compounds like Green Glue or upgrading to QuietRock pushes the cost to $8.00 to $15.00 per square foot for a premium sound isolation assembly.

Understanding what you're building — and why each component matters — is essential for getting value from a soundproofing investment. A proper sound isolation assembly for a duplex party wall starts with resilient channel (hat-shaped metal strips screwed horizontally across the studs at 16 or 24-inch spacing). The drywall is then screwed to the resilient channel rather than directly to the studs. This creates a physical break — a decoupling — between the wall structure and the drywall surface, which prevents sound vibrations from travelling through the framing. Resilient channel itself is inexpensive at $1.50 to $3.00 per linear foot, but the labour to install it correctly is critical.

The most important warning about resilient channel is this: a single screw driven through the drywall and resilient channel into the stud behind it completely short-circuits the sound isolation for that entire section of wall. This is the number one installation error, and it's devastatingly common with inexperienced crews. The screw creates a rigid connection — a sound bridge — that bypasses the decoupling the resilient channel provides. This is why soundproofing work must be done by contractors who specifically understand acoustic assemblies, not just any drywall crew.

Double drywall means two layers of drywall on the resilient channel, adding mass to the wall. More mass means more sound energy is absorbed rather than transmitted. A typical configuration uses two layers of 5/8-inch Type X drywall (which also satisfies the Ontario Building Code requirement for 1-hour fire-rated party wall separation in duplexes). The first layer is screwed to the resilient channel, and the second layer is screwed through into the first layer, with joints staggered by at least 12 inches so no joint lines align between layers.

For even better performance, Green Glue compound ($15 to $20 per tube, two tubes per 4x8 sheet) is applied between the two drywall layers. Green Glue is a viscoelastic damping compound that converts sound energy into heat as it passes between the layers. A double drywall assembly with Green Glue on resilient channel can achieve an STC rating of 55 to 60, well above the Ontario Building Code minimum of STC 50 for party walls between dwelling units. Without Green Glue, the same assembly achieves STC 48 to 54.

Alternatively, QuietRock — a specialty soundproof drywall with a viscoelastic polymer core — can replace the double drywall approach. A single layer of QuietRock achieves STC improvements of 15 to 20 points over standard drywall, but at $55 to $90 per 4x8 sheet compared to $20 to $28 for standard 5/8-inch Type X, the material cost is substantially higher. The labour savings from hanging one layer instead of two can partially offset this.

Here's a realistic cost breakdown for a shared wall measuring 200 square feet (a common size in Toronto duplexes — 25 feet long, 8 feet high), treating one side:

Standard sound isolation assembly — resilient channel, double 5/8-inch Type X drywall, acoustic caulk at perimeter: $1,200 to $2,000. Enhanced assembly — add Green Glue between layers, acoustic putty pads on electrical boxes, resilient channel on both sides of studs: $1,800 to $3,000. Premium assembly — QuietRock, resilient channel, acoustic caulk, putty pads, plus insulation upgrade to mineral wool batts in the cavity: $2,500 to $4,000.

Don't forget the flanking paths — sound doesn't just travel through the wall. It travels through the floor, ceiling, electrical outlets, HVAC ducts, and any gap in the assembly. Sealing all perimeter edges with acoustic caulk (not regular caulk), installing acoustic putty pads behind electrical boxes, and ensuring the ceiling and floor connections are properly detailed are all essential. A perfectly built wall with an unsealed electrical box will leak sound like a window left open.

This is specialist work — hire a drywall contractor with specific soundproofing experience. Ask to see examples of previous sound isolation projects and verify they understand resilient channel installation requirements. Find experienced contractors through the Toronto Construction Network directory at torontoconstructionnetwork.com/directory?trade=insulation.