How much does it cost to reroute ductwork to accommodate a new staircase in a GTA home?

Rerouting ductwork for a new staircase in the GTA typically costs $1,500–$6,000, with most projects landing in the $2,000–$4,000 range — but the final number depends heavily on how many duct runs cross the staircase path, what those ducts are made of, and how much of the surrounding ceiling or wall needs to be opened up to access them.

What Drives the Cost

The staircase itself doesn't care about your ductwork, but your ductwork almost certainly runs through exactly where the staircase needs to go. In most GTA homes built between 1945 and 1990, the main trunk line runs down the centre of the basement ceiling, and branch runs fan out perpendicular to it — which puts them directly in the path of any new staircase opening. Rerouting means disconnecting those runs, fabricating new sections that clear the staircase framing, reconnecting to the trunk, and resealing every joint with mastic and UL 181 foil tape.

Labour is the dominant cost in this type of work. A sheet metal worker in the GTA charges $80–$120 per hour, and a staircase reroute typically takes 8–20 hours depending on complexity. If you're moving a single small branch run, you're on the low end. If the main trunk line needs to be raised, offset, or split around the staircase opening, you're looking at a full day or more of custom fabrication and installation. Add drywall patching, painting, and finishing if the ducts run through finished spaces, and costs climb further — though that work is typically quoted separately by a general contractor.

Material costs for a typical reroute run $300–$800. Galvanized steel rectangular duct costs $12–$30 per linear foot installed, and you'll need custom-fabricated offsets and transitions to route around the new framing. If the existing ductwork is older galvanized steel in good condition, a skilled sheet metal worker can often reuse sections and fabricate only the transition pieces. If the existing ductwork is deteriorated, crushed flex duct, or asbestos-wrapped (common in pre-1960s Toronto homes), replacement costs increase significantly — and asbestos abatement adds $2,000–$5,000 before any ductwork work can begin.

GTA-Specific Considerations

Homes in established Toronto neighbourhoods — Leslieville, Riverdale, East York, Leaside, Roncesvalles, and similar areas — often have older duct systems that were designed for gravity-fed heating and later adapted for forced air. These systems frequently have large, low-hanging trunk ducts that are difficult to raise without significant rerouting. If your home is pre-1960 and you haven't had the ductwork assessed recently, budget for surprises.

A building permit is likely required for this project. The staircase itself requires a permit, and any significant duct modification associated with a permitted renovation is typically included in the mechanical scope. The City of Toronto mechanical permit fee is usually $200–$500 for this type of work. Your contractor should be pulling permits — if they suggest skipping it, that's a red flag.

Airflow impact is the other critical consideration. Rerouting ductwork isn't just a physical relocation — it changes the length of runs, the number of bends, and the static pressure throughout the system. Every 90-degree elbow in a duct run is equivalent to adding 10–15 feet of straight duct in terms of pressure drop. A sheet metal contractor doing this work properly will account for that, either by upsizing the rerouted section or minimizing bends. A contractor who just moves the duct without considering airflow may leave you with a room that barely heats or cools after the renovation.

Practical Tips

Get at least three quotes and ask each contractor specifically how they plan to maintain airflow to the affected registers after the reroute. Ask whether the new routing will require any duct upsizing. Confirm that all joints will be sealed with mastic — not grey cloth duct tape. If your home is pre-1960, ask about asbestos testing before any work begins.

Toronto Ductwork can match you with experienced local sheet metal contractors for a free estimate on your staircase reroute. Find ductwork professionals in your area through the Toronto Construction Network at torontoconstructionnetwork.com/directory?trade=hvac.