How much does it cost to add a second layer of drywall with Green Glue to every wall in a Toronto semi-detached?

Adding a second layer of drywall with Green Glue to every wall in a Toronto semi-detached will cost $8,000-$15,000 for materials and labour, depending on the home's size and layout complexity.

This soundproofing approach involves applying Green Glue viscoelastic compound between the existing drywall and a new layer of 5/8-inch drywall throughout the entire home. It's one of the most effective retrofit soundproofing methods, improving Sound Transmission Class (STC) ratings by 8-12 points over the existing single-layer walls.

Material costs for a typical 1,200-1,500 square foot Toronto semi break down to approximately $3,500-$5,500. You'll need roughly 60-80 sheets of 5/8-inch drywall at $20-$26 per sheet, plus 40-60 tubes of Green Glue compound at $18-$22 per tube. Each tube covers one 4x8 sheet with the recommended two 29-ounce tubes per sheet application pattern. Additional materials include screws, corner bead for any new outside corners, joint compound, tape, and primer.

Labour costs represent the majority of the expense at $4,500-$9,500. This project requires experienced drywall installers because the second layer installation is technically demanding. The existing electrical outlets, switches, and fixtures must be extended forward to accommodate the additional 5/8-inch thickness. All trim, baseboards, and casings need removal before installation and reinstallation afterward with extensions. The Green Glue must be applied in the correct serpentine pattern and the second layer installed within 15 minutes of compound application for optimal bonding.

GTA-specific considerations significantly impact the project scope and cost. Toronto's older semi-detached homes often have plaster walls rather than drywall, which complicates the attachment process and may require different fastening strategies. The shared party wall in a semi-detached already provides some sound isolation, so the biggest benefit comes from treating the front, back, and interior walls. Many Toronto semis have radiator heating with cast iron radiators that require careful work around the heating elements.

Electrical modifications add $1,500-$3,500 to the total project cost. Every outlet box, switch, and fixture must be extended forward or replaced with deeper boxes to accommodate the additional wall thickness. This work requires a licensed electrician and electrical permits in Toronto. HVAC registers and returns also need extension collars, adding another $300-$800 depending on the number of vents.

Practical installation challenges in Toronto semis include narrow staircases that make material delivery difficult, older homes with uneven walls that require shimming for the second layer, and potential asbestos in homes built before 1990. The project typically takes 5-8 days with a two-person crew - one day for prep and electrical rough-in, 2-3 days for Green Glue application and drywall installation, and 2-3 days for taping, finishing, and trim reinstallation.

Seasonal timing affects both cost and performance in the GTA. Winter installation in heated homes provides ideal conditions for Green Glue curing, but material delivery and disposal become more challenging. Summer installation requires careful humidity control during the finishing phase to prevent compound cracking.

Alternative approaches might better suit your specific noise issues and budget. If the primary concern is sound transmission through the shared party wall, treating just that wall costs $1,500-$3,500 and provides significant improvement. For airborne noise from outside traffic or neighbors, focusing on exterior walls and adding acoustic caulking around electrical penetrations delivers substantial results at $3,000-$6,000.

When to hire a professional - this is exclusively professional territory. Green Glue application requires precise timing and technique, electrical modifications need licensed work, and achieving invisible joints on the second layer over existing walls demands years of finishing experience. Poor installation wastes the expensive Green Glue compound and creates visible imperfections that show through paint.

The investment typically adds $4-$8 per square foot to your home's value in Toronto's competitive market, where noise control is increasingly important to buyers. However, the primary benefit is dramatically improved living comfort in your semi-detached home.

Need help finding a drywall professional experienced with soundproofing installations? Toronto Drywall Installers can match you with contractors who specialize in Green Glue applications through the Toronto Construction Network.