Short answer
In an Ontario real estate deal there usually isn’t time for a 91-day test. Common approaches: sellers provide a recent long-term result or install a system in advance; buyers run a professional short-term screening test during the conditional period and negotiate a price adjustment or holdback; or the buyer tests long-term after closing. Radon is fixable, so it rarely needs to stop a sale.
Key facts
- Long-term tests (91+ days) rarely fit inside a conditional period.
- A professional short-term test can screen a home before closing.
- Sellers: a long-term result or an installed system with documentation is a selling point.
- Ask your realtor and lawyer about clauses, credits or holdbacks.
The timing problem
Health Canada bases its guideline on long-term tests of at least three months. Ontario offer conditions are often measured in days. That mismatch is why radon in real estate takes a little planning: the right test for a decision and the time available rarely line up.
If you’re buying
- Ask for existing results. A long-term test done during a recent heating season, or documentation of an installed mitigation system, answers the question best.
- Screen during the conditional period. A short-term test by a certified professional, under closed-house conditions, can flag a likely problem. Treat it as a screen: high results are worth negotiating over, low results are worth confirming later.
- Negotiate a fix, not a fight. Because a typical mitigation costs roughly $2,000 to $3,500, many deals handle radon with a price adjustment, a credit or a holdback. Talk to your realtor and lawyer about wording.
- Test long-term after you move in, whatever happens before closing. It’s the result that matters for your family, and an early reading at two weeks tells you sooner whether a fix is likely.
If you’re selling
- Test early. If you’re planning to list in spring, a long-term test through the winter gives you a real result to share. A professional test also gives you an early reading at two weeks, so if the house is clearly high you have months, not days, to fix it before listing. How the early reading works.
- Mitigate before listing if needed. An installed, labelled system with before-and-after results and a working manometer turns a question mark into a feature.
- Keep documentation: test reports, the installer’s C-NRPP certification, the system design and warranty.
New homes and resale homes under warranty
If the home is within seven years of its original possession date, Tarion’s warranty may cover radon remediation above 200 Bq/m³, based on a long-term test of at least three months. The warranty generally transfers with the home for the remainder of its term. More on Tarion and radon.
What we provide for real estate
- Short-term screening tests scheduled around your conditional period.
- Written results suitable to share with the other party.
- Fixed-price mitigation quotes buyers and sellers can rely on in negotiations.
- Long-term follow-up testing after closing.
This page is general information, not legal advice. Talk to your realtor and real estate lawyer about clauses and holdbacks.
Common questions
Should I walk away from a house with high radon?
Rarely. Radon is one of the most fixable issues in a home; most systems install in a day and reduce levels by 90% or more. It’s usually handled through price or a holdback rather than a cancelled deal.
Can I get a radon test done before my condition deadline?
A professional short-term screening test can usually be scheduled within a typical conditional period. It’s a screen, not a final answer, so plan a long-term test after closing.
Do Ontario sellers have to disclose radon?
Disclosure obligations depend on the circumstances. Ask your realtor and lawyer. Providing a recent long-term result or documentation of a mitigation system is a simple way to build buyer confidence.