How to Claim the Tarion Radon Warranty in Ontario (Up to $50,000 Coverage)

If you bought a new home in Ontario in the past seven years, your statutory home warranty may already cover radon mitigation — up to $50,000, paid for by your builder. No separate insurance. No extra cost to you.

This is the Tarion radon warranty. Ontario is one of the only places in Canada where this kind of coverage exists. Most homeowners have never heard of it.

It's real. But it's not automatic. To claim it you need a specific kind of test, in a specific place, that shows a specific result. Get any of those wrong and your claim won't go anywhere.

This guide walks you through the four things that matter: who qualifies, what triggers coverage, the test that counts, and how to file.

For the full picture of how Canadian building codes deal with radon — including the 2024 Ontario Building Code and the new National Building Code 2025 — see our Canadian Building Codes and Radon guide.

The 60-second answer

• Coverage: Up to $50,000 of radon mitigation cost, performed by your builder during the warranty period (or by Tarion if your builder fails to act).
• Who qualifies: Owners of Ontario new homes whose Agreement of Purchase and Sale was signed on or after March 25, 2013, with possession in the past 7 years.
• What triggers coverage: A qualifying long-term radon test showing a certified lab report result above 200 Bq/m³ — the Health Canada guideline (becquerels per cubic metre is the unit Canada uses for radon).
• What test Tarion will accept: A long-term test of at least 3 months (and up to 12 months), using a device or testing professional certified by the Canadian National Radon Proficiency Program. Test in the basement, not a crawl space. The heating season is ideal but not required.
• How to file: Notify your builder in writing — including a copy of your lab report (such as the one we provide at RadonTest.ca) — then submit the right warranty form through Tarion's MyHome portal.

1. Are you eligible?

Two questions. Yes to both, along with a certified lab report showing your home is over 200 Bq/m³, and you're likely in.

Was your home enrolled with Tarion?

Almost all new homes built and sold by a licensed builder in Ontario are enrolled automatically. Check your closing documents for a Certificate of Completion and Possession.

When was your Agreement of Purchase and Sale signed?

Coverage runs for 7 years from your possession date — not from when the home was built, and not from when the agreement was signed. If you took possession in May 2020, your warranty is still active until May 2027.

Resale tip. The warranty travels with the home, not the original buyer. If you bought a resale home that's still within its 7-year window, you're likely still covered. To formally transfer the warranty into your name, contact your warranty provider at Tarion.

2. What actually triggers coverage

Three things must all be true:

• The home is within its 7-year warranty window.
• A qualifying long-term test has been conducted (RadonTest.ca provides this test and lab report).
• The test result is above 200 Bq/m³ — the Health Canada guideline.

Read that third condition carefully. Testing alone does not trigger coverage. A result at or below the guideline means there's no covered claim — there's nothing under warranty to remediate.

Testing is the gating step. The trigger is the elevated reading.

A note on the number. Health Canada's and Tarion's published language is "exceeds 200 Bq/m³." That means above 200 — a result at exactly 200, or below 200, does not exceed the guideline. In whole-number terms: 201 and higher qualifies. Anything else does not.

3. The test that qualifies

This is where most claims fall apart. Tarion's published guidelines have two requirements that must both be satisfied:

• The device or the testing professional must be certified through the Canadian National Radon Proficiency Program — Canada's body that certifies radon devices, professionals, and labs.
• The test must be a long-term test of at least 3 months, in line with Health Canada's measurement guidance.

A short-term test (less than 3 months) can start a claim, but Tarion will require a long-term confirmation test before approving mitigation. Tests in a crawl space are not accepted — measurement has to be in the basement.

When to test: heating season is best, but any season works

Radon levels rise in winter. Homes are sealed against the cold, furnaces run, and the natural "stack effect" pulls more radon up out of the ground than in warmer months.

For the most accurate annual-average reading, Health Canada recommends testing during the heating season — between October and April. A heating-season test captures your home's worst-case exposure window.

But you don't have to wait. A long-term test can be started any time of year. The alpha track detector in our kit can stay in place from 91 days up to 12 months. Two practical options if you're starting outside the heating season:

• Run a standard 91-day test — this still meets Tarion's 3-month minimum. The result may slightly underestimate your worst-case exposure since it misses the heating season, but it's a valid Tarion-eligible test.
• Run a longer test, up to 12 months — Health Canada considers 12 months optimal, and a test that spans both warm and cold seasons gives the most accurate annual-average reading possible.

Either way, the test counts toward your Tarion warranty as long as it's at least 3 months long and the result shows a level above 200 Bq/m³.

Two paths to a qualifying test

• Hire a certified professional to come measure your home with professional equipment and produce a formal report. Cost: typically $250 to $500.
• Use a do-it-yourself long-term test kit that meets the same standards: a device approved by the Canadian National Radon Proficiency Program, lab-analyzed by a certified Canadian lab.

For most homeowners, the do-it-yourself path is much simpler — and dramatically cheaper.

What our kit is

RadonTest.ca's 91-day alpha track test kit is purpose-built for the Tarion warranty workflow.

The detector is approved by the Canadian National Radon Proficiency Program. Lab analysis is performed by Lex Scientific in Guelph, Ontario — a Canadian lab certified by the Canadian National Radon Proficiency Program and accredited to ISO/IEC 17025.

You receive a written lab report at the end, emailed to you. This is the same report you will attach to your builder notification and your Tarion warranty claim. No separate paperwork to chase down.

$89, all-inclusive. Shipping to your door. Return shipping to the lab. Lab analysis. Written report. No surprise return-postage fees, no US lab routing, no separate analysis charges. Stays in Canada from start to finish.

Setup is simple. Your kit comes with picture-based placement instructions. We guide you through it. We include prepaid shipping back to a Canadian certified lab (no USA labs or hidden costs). No expertise required.

Order your test kit at radontest.ca →

4. How to file the claim

If your result comes back above 200 Bq/m³, here is the process. Follow the order — Tarion's process expects it.

Step 1 — Notify your builder in writing (with your lab report)

Before you submit anything to Tarion, give your builder a chance to address it. Email is fine. Keep dated copies of everything.

Your written notice should include:

• The radon test result, taken from your lab report (the average radon concentration in Bq/m³).
• A copy of the lab report itself, attached to the email.
• Your home's enrollment number, from your Tarion documents.
• A clear request for the builder to perform mitigation under your statutory warranty.

The lab report is the central piece of evidence. It identifies the device, the testing dates, the certification of the analyzing lab, and the result. Without it, you do not have a claim. The lab report you receive from RadonTest.ca contains all of this — it is the document Tarion's process is designed to receive.

Step 2 — Register at MyHome

Tarion's online portal for homeowners is myhome.tarion.com. You will need your home's possession date and enrollment number to register.

Step 3 — Submit the right warranty form

Radon falls under Tarion's 7-year coverage for environmentally harmful substances or hazards. Which form you submit depends on where you are in your warranty window:

• Year 1 (months 0 to 12): the Year-End Form, submitted in the last 30 days of the first year.
• Year 2 (months 12 to 24): the Second-Year Form.
• Years 2 to 7: the 7-Year Major Structural Defect / Environmentally Harmful Substances Form.

Upload your lab report and the certification details that came with your kit. Use the same lab report you sent to your builder.

Step 4 — The builder repair period

Submission triggers an initial 120-day builder repair period. The builder is expected to investigate and arrange mitigation, performed by a mitigation professional certified by the Canadian National Radon Proficiency Program. For homes built before 2012, Tarion may fund mitigation directly. For newer homes, Tarion typically directs the builder.

Step 5 — Conciliation if it is not resolved

If the issue is not resolved during the repair period, request a Tarion conciliation. Tarion assesses the claim and, if warranted, ensures resolution. Conciliation timing rules changed on May 1, 2024 — confirm the current rule with Tarion before filing.

Step 6 — Verify after mitigation

Once a mitigation system is installed, do a post-mitigation test to confirm levels are below 200 Bq/m³. Many homeowners run an independent verification test in addition to the mitigator's own.

5. Five mistakes that kill claims

• Testing in a crawl space. Tarion requires basement measurement. Crawl-space-only readings are excluded.
• Using a short-term test as your only evidence. A short-term test can begin the conversation; only a long-term test (3 months or more) authorizes mitigation.
• Notifying the builder without the lab report attached. Tarion's process requires documented evidence of the elevated reading. Verbal claims and screenshots are not enough.
• Missing a form deadline. Form windows are precise and unforgiving. A claim outside the relevant window is generally not eligible.
• Hiring an uncertified mitigator. Mitigation must be performed by a professional certified by the Canadian National Radon Proficiency Program. Verify at c-nrpp.ca before any work begins.

Frequently asked questions

Does Tarion reimburse the cost of the test?

No. Tarion does not pay for the test. The homeowner pays. Coverage applies to mitigation work only.

Can I test in summer instead of winter?

Yes. A long-term test (3 months minimum) can be started any time of year and still qualifies for Tarion warranty purposes. Health Canada's recommendation is the heating season for the most accurate annual-average reading. If you start outside heating season, consider running the test longer — up to 12 months — so it spans both warm and cold months.

My result was 180 Bq/m³. Can I claim?

No. That is below the Health Canada guideline of 200 Bq/m³, so Tarion will not cover mitigation. Health Canada notes that any reduction in radon exposure is beneficial, and many homeowners voluntarily mitigate at lower levels for personal peace of mind. That choice is yours. (If your result had been above the guideline, our what-to-do-if-your-radon-level-is-above-200 guide walks through your next steps.)

My possession date was 8 years ago. Can I still claim?

Coverage runs for 7 years from possession. After that, the radon warranty has expired, even if you have never tested. (Test anyway. The radon does not go away because your warranty did.)

Does Tarion cover health damages from radon?

No. The warranty covers mitigation cost only. Personal injury, illness, and damage to personal property are not covered.

I bought a resale home. Am I covered?

If the home is within its 7-year warranty window from the original possession date, yes. Contact Tarion to formally transfer the warranty into your name.

Is RadonTest.ca affiliated with Tarion?

No. RadonTest.ca is an independent Canadian radon test kit provider. We are not affiliated with, endorsed by, or licensed by the Tarion Warranty Corporation. The Tarion name is used in this article only to describe Ontario's statutory new home warranty program. Tarion's published rules govern any specific claim.

Test your home. It's the only way to know.

If your Ontario home is within its 7-year Tarion window, the cost of mitigation could be covered. The cost of finding out is the test — and that's on you.

Our 91-day kit is built for this exact use case:

• Long-term test, 91 days — meets the Tarion minimum. Run it longer (up to 12 months) for the most accurate result.
• Detector approved by the Canadian National Radon Proficiency Program
• Analyzed by Lex Scientific in Guelph, Ontario — Canadian lab, C-NRPP certified, ISO/IEC 17025 accredited
• Written lab report — the document you attach to your builder notification and Tarion claim
• $89 all-inclusive: kit, both-way shipping, lab analysis, written report
• Stays in Canada from start to finish

Order your test kit at radontest.ca →

$89 — all in. No surprise fees.

If your test comes back high, you will have a result Tarion accepts so you can mitigate. If it comes back low, you will have peace of mind. Either way, you will know.

Important disclaimers

This article is general information about the Tarion radon warranty as of May 2026. It is not legal, professional, or warranty advice.

RadonTest.ca is independent from Tarion. We are not affiliated with, endorsed by, or licensed by the Tarion Warranty Corporation. The Tarion name is used in this article in a descriptive sense only, to identify Ontario's statutory new home warranty program. RadonTest.ca is not authorized to provide warranty advice or warranty assistance, and our role is limited to providing radon test kits and laboratory analysis through our partner Lex Scientific Inc.

Tarion's published rules govern any specific claim. Eligibility, coverage limits, form windows, conciliation timing, and procedural rules are determined solely by Tarion. RadonTest.ca makes no representation that any specific home, test, or claim will qualify for coverage. A test result at or below the Health Canada guideline of 200 Bq/m³ does not exceed the guideline and would not, on its own, support a Tarion radon claim.

Always verify directly with Tarion before relying on this information. Visit tarion.com or call 1-877-9-TARION (1-877-982-7466). For radon testing protocol, consult Health Canada at canada.ca/health-canada/radon and the Canadian National Radon Proficiency Program at c-nrpp.ca.

RadonTest.ca makes no warranty as to the completeness or accuracy of the information herein and accepts no liability for decisions made in reliance on this article. Readers should independently verify any information that bears on a transaction, a claim, or a construction decision.