Radon Testing in Toronto: Why It Matters, What It Costs, How to Start
About 1 in 22 downtown Toronto homes tests above Health Canada’s radon guideline of 200 Bq/m³.
Toronto isn’t a radon hot spot like Guelph or Ottawa. But “lower average” is not “no risk.” The problem is that the risk hides in specific homes, not whole neighbourhoods.
The short version:
- Downtown Toronto’s average home radon sits near 43 Bq/m³, well below the 200 Bq/m³ guideline
- Even so, about 4.5 percent of homes test high, which is thousands of houses
- Old pre-war homes in the Annex, Cabbagetown, and Riverdale are the higher-risk group
- Most high-floor condos are low risk. Ground and second-floor units are the ones to check
- A professional test at Breathe Radon Free is $99 flat, takes 3 to 7 days, and comes with a written report
- New builds bought since February 2021 may have builder-paid mitigation through Tarion
Does Toronto really have a radon problem?
Yes, but it’s uneven. The city average is low. The spread between homes is wide.
Radon comes from uranium breaking down in soil and rock. It seeps up through cracks in the foundation and gathers in the lowest lived-in level. Toronto sits mostly on glacial till over sedimentary bedrock, which puts out less radon than the granite further north.
That’s why the downtown average is near 43 Bq/m³.
What raises the odds in Toronto is old housing. The city has one of the oldest home inventories in Canada.
Pre-war homes in the Annex, Cabbagetown, Riverdale, Roncesvalles, and the Junction often have stone or rubble foundations. Many have dirt-floor cellars and decades of small cracks. Those are easy paths for soil gas.
The pattern is simple. The older the home, and the more time your family spends in a finished basement, the more testing matters.
Health Canada and the Canadian Cancer Society both say every home should test at least once, whatever the local average.
Toronto condos: which floors need a test?
Radon is heaviest at ground level, because that’s where it enters from the soil. It thins out fast as you go up.
If you live above the third or fourth floor, you can almost always skip the test. By floor 4, levels are usually 80 percent diluted. By floor 10, radon is not a practical concern.
The units worth checking are lower down:
- Floors 1 to 3 in an older mid-rise
- Any unit sitting directly above a parking garage or service shaft
- Ground-floor townhomes and stacked units
- Basement apartments in older houses
Basement apartment tenants have one of the highest exposure profiles in the city. Ground-level living, old foundations, and long hours indoors all stack up. As a renter, you can run a long-term kit on your own without the landlord’s help.
How much does radon testing cost in Toronto?
Here’s what your real options cost in 2026.
| Option | Cost | Time | Accuracy | Best for |
|---|---|---|---|---|
| DIY alpha-track kit | $30 to $60 | 4 to 8 weeks | Moderate | Budget-first, no rush |
| Professional short-term (ours) | $99 | 3 to 7 days | High | Most homeowners |
| Long-term (Health Canada gold standard) | $299 | 91+ days | Highest | If you can wait a season |
| Real estate transaction test | $399 | 48 to 72 hours | High | Closing within 30 days |
Our $99 test uses a calibrated continuous radon monitor. We drop it off, leave it for at least 72 hours, pick it up, and email you a written report.
The report shows hour-by-hour readings, your peak and average, and a plain-English read on what it means. A photo of a number on a screen is not a report. You’ll want real documentation if you ever sell.
The cheapest mistake in radon is not testing at all. A $99 test tells you where you stand. Guessing tells you nothing, and Toronto’s older homes are exactly where guessing goes wrong.
Same $99 price applies across the whole city. That includes the Yonge corridor, Queen West, the Annex, Cabbagetown, Riverdale, Roncesvalles, the Junction, Scarborough, North York, and Etobicoke. No distance surcharge.
Want the number for your home? Book a $99 test in 60 seconds or call (647) 788-8797.
When should you test in Toronto?
Best window: late fall through early spring, roughly November to April.
Radon peaks in winter. The ground freezes, so soil gas pushes into your warm basement instead of escaping outside. You also keep windows shut, so the gas has nowhere to go.
A summer test can read 30 to 50 percent lower than a winter test in the same house. So if you test in summer and land just under the guideline, treat that as a caution, not an all-clear.
Other good moments to test:
- Right after you buy a home
- After a basement finish, sump install, or foundation work
- Two years after any mitigation system goes in
- Once every five years, even after a low result
DIY test kit vs hiring a pro
Both work. The honest answer is that many Toronto homeowners can start with a cheap kit and be fine. Here’s how to choose.
| DIY kit | Professional test (BRF) | |
|---|---|---|
| Cost | $30 to $60 | $99 flat |
| Time to result | 4 to 8 weeks (mail-in lab) | 3 to 7 days |
| Data | One average number | Hour-by-hour readings |
| Placement | You set it up (easy to get wrong) | We follow Health Canada protocol |
| Written report | Basic lab sheet | Full report you can use for a sale or Tarion claim |
| Best for | A first screen, no deadline | A sale, a Tarion claim, or a fast answer |
Go DIY when you just want a first look, you’re not selling, and you can wait a couple of months. Buy a long-term alpha-track kit and place it in the lowest lived-in level.
Hire a pro when you’re buying or selling, you’re filing a Tarion claim, your DIY result came back near the line, or you simply want it done right and fast.
One caution for Toronto. The C-NRPP public directory lists very few certified pros serving the downtown core.
New Toronto builds: the Tarion path
Did you buy a new condo, townhouse, or house from a builder on or after February 1, 2021?
If so, your Tarion New Home Warranty covers radon mitigation up to $50,000, paid by the builder, for the full 7-year term.
That coverage switches on the moment a proper test shows radon at or above 200 Bq/m³. Your cost is the test itself, plus the time to file the claim with the report attached.
Toronto has added a lot of new stacked towns and low-rise builds since 2021. Many of those owners have no idea the coverage exists. If you’re inside your 7-year window, a $99 test is the smallest possible step toward a builder-funded fix.
Read our full Tarion warranty guide for the eligibility checklist and the claim steps.
What to do next
Radon is invisible and has no smell. You can’t feel it, and you can’t guess it. The only way to know is to test.
If your result is under 200 Bq/m³, we’ll tell you that and suggest a five-year re-test. We don’t push mitigation on homes that don’t need it.
If it’s high, we walk you through the options. That includes the Tarion path if your home qualifies, or a referral to a qualified mitigator if it doesn’t.
Start with a test. Ours is $99, takes 3 to 7 days, and you get a written report you can actually use.
- Get a $99 radon test for your Toronto home
- See our Downtown Toronto service area
- New to this? Read our plain-English guide to radon testing
Frequently asked questions
Is Toronto a high-radon city?
No, Toronto is a lower-average city, near 43 Bq/m³ downtown. But about 4.5 percent of homes still test above the 200 Bq/m³ guideline. That’s thousands of houses, and older homes carry most of the risk. Every home should test once to be sure.
I live in a downtown Toronto condo. Do I need to test?
It depends on your floor. Floors 1 to 3 can have real exposure, especially above a parking garage. By floor 4 the gas is mostly diluted, and by floor 10 it’s negligible. A 25th-floor glass tower unit does not need a test.
Which Toronto neighbourhoods are higher risk?
Older pre-war areas with stone or rubble foundations top the list. Think the Annex, Cabbagetown, Riverdale, Roncesvalles, and the Junction. Newer high-floor condos test very low. The single biggest factor is the individual home, not the postal code. To learn how to read a result, see our guide to radon levels.
Do you actually service downtown Toronto?
Yes. The whole core is inside our service area, from the Yonge corridor to Queen West, the Annex, Cabbagetown, Riverdale, Roncesvalles, and the Junction. Same $99 price as the suburbs, no distance surcharge. Few C-NRPP pros list the downtown core, which is exactly why we serve it.
Can I just open windows instead of mitigating?
Short-term, opening windows does lower radon by letting in fresh air. Long-term, it’s not a real fix, especially through a Toronto winter. A proper mitigation system is permanent and uses less energy than heating a house with a window cracked open all season. If your test comes back high, see our guide to radon mitigation in Toronto for cost, condo rules, and the Tarion path.
Authored by the Breathe Radon Free team. Every claim in this guide is backed by a primary source linked above. Full bibliography at /sources.
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