What is the average cost to replace rusted-out ductwork in a Toronto home crawl space?

Replacing rusted-out ductwork in a Toronto home's crawl space typically costs $2,500 to $8,000, with most projects landing in the $3,500 to $6,000 range for an average-sized home. The wide price range reflects the significant variation in crawl space accessibility, extent of damage, and the complexity of the replacement layout.

Crawl space ductwork in GTA homes takes a beating. Toronto's freeze-thaw cycles — over 50 per winter — cause expansion and contraction at every joint, loosening connections over time. Moisture from the ground migrates upward, and in homes without a proper vapour barrier on the crawl space floor, that moisture condenses on cold duct surfaces throughout the winter. Over years, this relentless cycle of condensation and drying corrodes galvanized steel from the outside in, creating rust holes that leak conditioned air into the crawl space. Homes in areas with high water tables — parts of Scarborough, Pickering, Ajax, and low-lying sections of Etobicoke near the Humber — experience accelerated corrosion due to elevated crawl space humidity.

The replacement process starts with a thorough assessment of the existing system. A contractor will need to determine whether just the branch runs are rusted or if trunk lines are also compromised. For a typical 1,200 to 1,800 square foot GTA bungalow with a full crawl space, replacing all supply and return ductwork runs $3,000 to $6,000 including new galvanized steel or spiral round duct, fittings, register boots, mastic sealing at every joint, and insulation. If the trunk line and plenum connections also need replacement, costs climb to $5,000 to $8,000. Crawl space work carries a labour premium of 20 to 40 percent compared to open-basement installations because contractors are working in confined, uncomfortable conditions — heights of 3 to 4 feet are common, and some crawl spaces are barely 2 feet.

Before new ductwork goes in, address the moisture source that caused the rust in the first place. Installing a 6-mil polyethylene vapour barrier over the crawl space floor costs $500 to $1,500 and is essential for protecting the new ductwork. Without it, the replacement ducts will follow the same corrosion path as the originals. All new ductwork in the crawl space should be insulated with R-8 duct wrap minimum to prevent condensation — this adds $500 to $1,200 to the project but pays for itself in energy savings and duct longevity.

If the existing ductwork predates 1985, have it tested for asbestos before removal. Asbestos tape and insulation were commonly used on duct joints and fittings, and disturbing this material without proper abatement is both dangerous and illegal in Ontario. Testing costs $300 to $600, and professional removal adds $2,000 to $5,000 if asbestos is found.

Get at least three quotes from contractors willing to physically enter and assess the crawl space — not just peer in from the access hatch. Confirm WSIB coverage, as crawl space work carries higher injury risk. Toronto Ductwork can match you with experienced local ductwork contractors through the Toronto Construction Network at no charge.