Can I be liable if I hide asbestos from my Ottawa contractor?

Yes, hiding asbestos from a contractor can expose you to serious legal and financial liability under Ontario law. The short answer is: disclose it, in writing, before anyone starts work.

What Ontario law says about disclosure

Section 30 of the Occupational Health and Safety Act requires an owner to determine whether designated substances are present at a project site and to prepare a list before work begins. Asbestos is one of the 11 designated substances listed in O. Reg. 490/09. If the work is tendered, that list must go into the tendering documents. If a contractor signs a contract without receiving the list, section 30(5) makes the owner liable to the constructor and every contractor and subcontractor who suffers a loss from discovering a designated substance the owner ought reasonably to have known about.

That phrase, "ought reasonably to have known", matters. Health Canada says that before 1990 asbestos was mainly used for insulating buildings and homes, which is why the age of a house matters to what an owner ought reasonably to have known. How section 30 applies to a house the owner lives in is not settled: the asbestos regulation exempts owner-occupiers, section 30 itself has no residence exemption, and Ontario's guide says it applies to owners of residential properties who undertake projects. If you are unsure, ask your contractor or the Ministry of Labour. The exemption covers a home the owner or their family lives in, and a building of up to four units where the registered owner or family lives in one of them. A landlord who doesn't live in the building, a building of more than four units, and commercial property are not covered.

The owner-occupier exemption in O. Reg. 278/05 removes certain duties from your shoulders as an owner, but it does not remove the contractor's obligations. The contractor you hire is still bound by the regulation in full: the Type classification, the inspector notice for Type 3 work, the training requirements, the clearance air test, and the waste rules under Ontario Regulation 347. If asbestos you knew about is disturbed without the controls its Type requires, the losses that follow can become the owner's liability under section 30(5).

Practically speaking, the costs compound quickly. If suspect material is found during the work, O. Reg. 278/05 section 10(8) requires the constructor or employer to immediately notify, orally and in writing, an inspector at the Ministry of Labour, the owner, the contractor, and the joint health and safety committee or representative. A Type 3 removal, which covers more than one square metre of friable material, requires a Ministry of Labour inspector notice before it can begin, workers who completed the Asbestos Abatement Worker Training Program, and a clearance air test once the enclosure is dry. Published Ontario contractor prices read in September 2026 put asbestos removal at roughly $8 to $15 per square foot and an air clearance test at about $300 to $800.

What to do before you hire anyone: get a pre-renovation inspection with asbestos testing. Published prices for that run roughly $250 to $1,300 depending on the size of the building and the number of samples. Give the written report to every contractor before they quote. Ask each one to confirm in writing which Type their work falls under and how they plan to handle disposal under Regulation 347.

If material has already been disturbed, stop the work, don't disturb it further, and have it tested by a professional.