Radon when buying or selling a house: common questions

Yes. Health Canada says to test before you sell and after you buy, but not during the sale itself.

Health Canada's guidance to real estate professionals explains why. A three-month test does not fit the time a buyer has to remove conditions from an offer. Testing before you sell means a low result can become a selling feature, and mitigation before listing takes the issue out of negotiation. After you buy, Health Canada says to run a long-term test once you have moved in.

See how radon testing fits into buying or selling a home

Not to decide whether a home is above the guideline.

Health Canada says short-term measurements should never be used to decide whether a home is above the Canadian guideline or needs fixing. Where a buyer wants certainty and there is no time for a long-term test, Health Canada's guidance describes a holdback in the contract of purchase and sale. An agreed amount is held in trust while a long-term test runs after closing. As Health Canada describes it, the funds go to mitigation if the result is above 200 Bq/m³, or back to the seller if it is not.

See how radon testing fits into buying or selling a home

In Ontario, sometimes.

Under Tarion's guideline FH 1.19, the warranty covers repairs when a long-term test of 91 days or more in the lowest level reads above 200 Bq/m³. The cause must be a Building Code violation or a builder defect. Tarion says coverage is up to $50,000 where the purchase agreement was signed after 1 February 2021, and up to $15,000 before that.

Tarion says coverage runs seven years from first possession and stays with the home. Freehold owners arrange their own testing. For other homes, testing depends on the home type and where the radon is found.

Outside Ontario, Health Canada says radon will likely fall within provincial warranty systems. Ask your provincial new home warranty provider.

See how radon is handled in new homes and warranties