What is the cost to install fire dampers in ductwork for a Toronto duplex conversion?

Installing fire dampers in ductwork for a Toronto duplex conversion typically costs $200 to $500 per damper, with most conversions requiring 4 to 8 dampers for a total project cost of $1,200 to $4,000 including labour, materials, and inspection. This is a non-negotiable code requirement — the Ontario Building Code mandates fire dampers wherever ductwork penetrates a fire-rated assembly, and the fire separation between dwelling units in a duplex is one of the most critical fire-rated assemblies in the building.

When you convert a single-family Toronto home into a legal duplex, the City of Toronto Building Division requires a fire separation between the two units, typically rated for one hour. Every point where a supply duct, return duct, or exhaust duct crosses that fire separation needs a fire damper. These are spring-loaded metal assemblies installed inside the duct at the wall or floor penetration. When the fusible link reaches approximately 74 degrees Celsius, the damper slams shut and prevents fire and smoke from spreading through the duct system into the other unit. The damper itself costs $80 to $200 depending on size and type, and installation runs $120 to $300 per damper because the duct must be cut, the damper fitted precisely, the connection sealed, and access panels installed so the damper can be inspected and reset after activation.

For a typical GTA duplex conversion, plan on fire dampers in these locations: every supply duct that crosses the unit separation, every return duct crossing, the bathroom exhaust duct if it serves one unit but passes through the other unit's space, and any shared trunk line that feeds both units. Most conversions need a minimum of 4 dampers, and complex layouts with multiple duct crossings can require 6 to 8. Your mechanical permit application will include a drawing showing every fire damper location, and the City of Toronto inspector will verify each one during the rough-in inspection.

Beyond the dampers themselves, duplex conversions in Toronto often trigger broader ductwork changes. If both units share a single furnace and duct system, you may not meet the OBC requirement for independent mechanical systems in each unit — many duplex conversions require separate furnaces, which means separate duct systems. This can push ductwork costs to $5,000 to $15,000 per unit. If separate systems are required, fire dampers are still needed where any duct penetrates the fire separation.

Budget $200 to $800 for the City of Toronto mechanical permit fee, and factor in the TSSA inspection if any gas connections are involved. An experienced ductwork contractor familiar with Toronto duplex conversions will know exactly which damper locations the inspector expects to see. Get matched with a local ductwork professional through the Toronto Construction Network to get accurate quotes for your specific layout.