What's the typical cost to retrofit sound isolation clips and double drywall on a townhouse party wall?

Retrofitting sound isolation clips with double drywall on a townhouse party wall in Ottawa typically costs between $3,500 and $7,500 per wall, with most projects landing around $18 to $25 per square foot installed. A standard townhouse party wall is roughly 20 to 25 feet long and 8 feet high, giving you 160 to 200 square feet of surface area to treat. This is one of the most common and effective soundproofing upgrades in Ottawa, where townhouse living in communities across Barrhaven, Kanata, Stittsville, and Orleans means sharing walls with neighbours whose lifestyle may not match yours.The process begins with removing the existing drywall on your side of the party wall to expose the stud framing. Your contractor will then fill the stud cavities with Rockwool Safe'n'Sound acoustic mineral wool — a step many townhouse builders skip during original construction, leaving empty cavities that transmit sound freely. Next, sound isolation clips (such as RSIC-1 at $4 to $7 each) are fastened directly to the studs at specific spacing intervals, and hat channel is snapped into the clips to create a resilient framework that is mechanically decoupled from the stud wall. This decoupling is the key — it breaks the direct vibration path that carries sound through the structure.The Double Drywall AssemblyTwo layers of 5/8-inch Type X drywall are then screwed to the hat channel — never into the studs behind — with Green Glue compound applied between the two layers at roughly one tube per 32 square feet. The edges are sealed with acoustic caulk that remains permanently flexible, ensuring no rigid bridges form around the perimeter. This complete assembly — isolation clips, hat channel, mineral wool, double drywall with Green Glue, and acoustic caulk — can achieve STC 55 to 63, a substantial improvement over the STC 38 to 45 that most Ottawa townhouse party walls deliver as-built.The material costs break down roughly as follows: isolation clips and hat channel at $3 to $5 per square foot, Rockwool Safe'n'Sound at $1.20 to $1.80 per square foot, two layers of 5/8-inch Type X drywall at about $1.50 per square foot, Green Glue at roughly $0.50 to $0.70 per square foot, and acoustic caulk and putty pads at $100 to $200 for the wall. Labour accounts for 40 to 60 percent of the total, covering demolition, insulation, clip installation, drywalling, mudding, and painting. Ottawa rates for this skilled work run 10 to 15 percent below equivalent GTA pricing.A critical detail that separates professional results from disappointing ones: every electrical outlet in the party wall needs an acoustic putty pad wrapped around the box, and ideally the outlets on your side should be offset from those on the neighbour's side so they are not back-to-back. Also ensure the contractor seals the top and bottom plates where the wall meets the ceiling and floor — these junctions are common flanking paths that undermine even excellent wall assemblies. Under the Ontario Building Code, party walls between dwelling units must achieve STC 50, so this retrofit comfortably exceeds the minimum requirement.For a townhouse party wall retrofit, having a professional assess the existing wall construction before committing to a quote is essential — some townhouses have steel studs, some have wood, and the existing insulation situation varies widely. Sound IQ from Ottawa Soundproofing can help you understand what to expect, and the Ottawa Contractor Directory at justynrookcontracting.com/directory connects you with acoustic professionals experienced in townhouse soundproofing across the Ottawa region.Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:Reno's by Daniel FrauwallnerJC CarpentryART DRYWALL AMD PAINTINGDemontigny CarpentryPrism ServicesView all contractors →