Radon Mitigation in Toronto: Cost, Process, and Whether You Need It
About 1 in 22 downtown Toronto homes tests above Health Canada’s radon guideline of 200 Bq/m³.
Most Toronto homes never need mitigation. The city average sits near 43 Bq/m³, well under the guideline.
The short version:
- Radon mitigation in Toronto runs $2,800 to $3,800 for a standard home.
- Only mitigate if a real test reads at or above 200 Bq/m³. Test first, always.
- Toronto needs mitigation less often than Guelph or Ottawa. Lower bedrock radon is why.
- A good system cuts indoor radon by 80 to 99 percent.
- Condo mitigation adds permit and condo board steps that a house doesn’t have.
- New builds bought since February 1, 2021 may have the fix paid by the builder through Tarion.
Does your Toronto home even need mitigation?
Most Toronto homes don’t. But some do, and only a test tells you which.
Radon comes from uranium breaking down in soil and rock. It seeps up through cracks in the foundation and pools in the lowest lived-in level. Toronto sits mostly on glacial till over sedimentary bedrock. That puts out less radon than the granite up north.
That’s why Toronto needs mitigation less often than Guelph or Ottawa. Guelph’s average is near 80 Bq/m³. Ottawa runs higher still. Toronto’s 43 Bq/m³ average is one of the lowest in the region.
But an average hides the homes at the high end. Old pre-war houses in the Annex, Cabbagetown, and Riverdale often have stone or rubble foundations and dirt-floor cellars. Those are easy paths for soil gas. A 1910 house with a finished basement bedroom can read high even when the street average is low.
Here’s the rule. Never mitigate on a hunch. Mitigate on a number.
You need a real radon test at or above 200 Bq/m³ before you spend a dollar on a system. A $99 test protects you from a $3,000 mistake. If you haven’t tested yet, start with our guide to radon testing in Toronto.
What radon mitigation costs in Toronto
Our published price for a standard Toronto home is $2,800 to $3,800. That covers the install, a post-mitigation verification test, and a 5-year workmanship warranty.
Most reputable Ontario installers land in the same range. The work isn’t harder in Toronto than anywhere else. Health Canada’s mitigation protocols are the same across Canada.
A few things move the number:
| Cost driver | Cheaper end | Pricier end |
|---|---|---|
| Foundation | Single full basement | Rubble or stone foundation, common in pre-war homes |
| Home size | Under 2,000 sq ft | Over 3,500 sq ft (may need two suction points) |
| Pipe route | Short run, exits side wall | Long run through finished living space |
| Property type | Detached house | Condo or townhouse with shared structure |
Old Toronto foundations are the wildcard. A crumbly rubble foundation is harder to seal than a clean poured slab. That can push a downtown heritage home toward the top of the range.
Watch out for quotes above $5,000 on a standard detached home. That’s a yellow flag. Get a second quote before you sign.
We cover the full mechanics in our Canada-wide mitigation cost guide if you want the deeper version.
Condo and apartment mitigation: the extra rules
This is where Toronto is different from the suburbs. The city is full of condos, and a condo mitigation job is not a solo decision.
Most high-floor condo units don’t need testing at all. Radon is heaviest at ground level. By the fourth floor it’s usually diluted, and by the tenth it’s a non-issue. The units that can read high are ground-floor and basement-level, or any unit sitting right above a parking garage.
If a low-floor unit does test high, mitigation gets complicated fast:
- The condo board owns the structure. You can’t drill through a shared slab or run a pipe up a shared wall without board approval.
- A building-wide problem needs a building-wide fix. One high unit often means the units next door read high too. That’s the board’s job, not yours.
- Toronto may require a building permit for work that touches the structure or the exterior. Your installer should pull it, not you.
For a stacked townhouse or a ground-floor unit you own outright, a normal sub-slab system can still work. But start by talking to your property manager. The last thing you want is to pay for a system the board then makes you remove.
The Tarion path: your builder may pay
Toronto has added a lot of new stacked towns, low-rise builds, and condos since 2021. Many of those owners have no idea what their warranty covers.
Ontario is the only province with radon coverage built into its new home warranty.
- Bought from a registered builder
- Purchase agreement signed on or after February 1, 2021
- Still inside the 7-year Tarion warranty term
Then your builder is on the hook for mitigation if a certified test reads at or above 200 Bq/m³. Tarion covers up to $50,000 of the work.
That pays for the full system in almost every case. Your cost is the test ($99 with us) and the time to file the claim.
The cheapest high-impact move for a Toronto new-build owner is a $99 test. If it comes back high and you’re inside your 7-year window, your builder funds the fix, not you.
We walk test customers through the Tarion claim process for free.
DIY radon mitigation: what’s smart, what’s not
No Ontario law forces you to hire a certified installer for a home mitigation job. You can legally do the work yourself. That doesn’t make it wise.
What you can DIY safely
A handful of tasks are fine for a handy homeowner:
- Seal visible slab cracks. A tube of polyurethane caulk slows radon entry. About $15.
- Swap a sump pit cover for a sealed one. A $30 part, a 20-minute job.
- Replace a failed fan on an existing system. Cut power, unclamp the couplings, slide the new fan in. About 30 minutes.
What you should hire out
Almost everything else:
- Designing a full system from scratch. Sizing the suction point, picking the fan, routing the pipe. Get it wrong and your radon stays high while you think it’s fixed.
- Drilling through an old Toronto foundation. Rubble and stone foundations are unpredictable. You can hit rebar, old drain tile, or hydronic lines.
- Anything in a condo, or anything tied to a Tarion claim. Condos need board approval. Tarion needs a C-NRPP certified installer. DIY work voids that whole path.
A DIY full system saves $1,500 to $2,000 in labour. But it skips the verification test that proves your radon actually dropped. For a home that qualifies for Tarion, that’s a bad trade.
One caution for Toronto. The public C-NRPP directory lists very few certified pros serving the downtown core.
How a Toronto install works
Most jobs run 4 to 6 hours, start to finish. The steps:
- Site visit. About 30 minutes. The installer checks the foundation, plans the pipe route, and sizes the fan. Firm quote within a day.
- Install day. Drill a suction point, dig a small pit under the slab, seal and run the pipe, mount the fan outside, and cap it above the roofline.
- Post-mitigation test. A new radon test 30 days after install. It confirms the system actually dropped your number. A good installer pays for this test.
The fan uses about 60 watts. That adds $5 to $10 a month to your hydro bill. A properly installed exterior fan is quieter than a dishwasher.
A good system drops indoor radon by 80 to 99 percent.
Grants that help with the cost
Tarion is the biggest help, but it’s not the only one.
The Canadian Lung Association runs the Lungs Matter Grant. It covers up to $1,500 of mitigation for income-eligible homeowners.
If you’re buying or selling and a test comes back high, the cost can become a credit at closing. The seller pays through a price cut or installs the system before the deal closes.
The Canadian Cancer Society calls radon the top cause of lung cancer in people who’ve never smoked.
Where Breathe Radon Free fits
We’re an Ontario-based testing service, owner-led, based in Guelph and serving the Greater Toronto Area plus surrounding Southern Ontario. The whole Toronto core is inside our service area, with no distance surcharge.
We publish our prices:
- Residential test: $99 flat. 3 to 7 days, written report.
- Real estate transaction test: $399. Faster turnaround for closings.
- Long-term test: $299. 91-day, for ongoing residential.
- Mitigation: $2,800 to $3,800. Full system, post-mitigation verification, 5-year warranty.
- Tarion claim help: free for test customers.
If your test reads under 200 Bq/m³, we’ll tell you. We don’t sell mitigation to homes that don’t need it.
See full pricing and book a test. Or request a mitigation quote. You can also read about our Downtown Toronto service area.
Frequently asked questions
Do I need mitigation if my Toronto home tested high?
Only if a proper test reads at or above 200 Bq/m³. One high short-term test isn’t an emergency, but it is a reason to act within two years. If your reading sits between 100 and 200, confirm it with a long-term test before you spend on a system.
Is mitigation cost different in Toronto than the rest of the GTA?
Mostly no. Standard detached homes across the GTA run $2,800 to $3,800. Toronto’s difference is at the edges. Pre-war homes with rubble foundations can cost more to seal, and condos add permit and board steps that a house doesn’t have.
My Toronto home is a new build. Does Tarion really pay?
Yes, if you bought from a registered builder on or after February 1, 2021 and you’re inside the 7-year warranty. A C-NRPP certified test at or above 200 Bq/m³ triggers builder-funded mitigation up to $50,000.
Can I mitigate my downtown condo on my own?
Not without approval. The condo board owns the shared structure, so you can’t drill a shared slab or run a pipe up a shared wall without sign-off. A high reading in one low-floor unit often points to a building-wide fix, which is the board’s job. Start with your property manager.
How long does mitigation take?
Most installs run 4 to 6 hours. The site visit is another 30 minutes on a separate day. You get a post-mitigation test 30 days later to confirm the system works.
Will mitigation raise my hydro bill much?
No. The fan runs on about 60 watts, so it adds roughly $5 to $10 a month. That’s the cost of keeping your indoor air below the guideline year-round.
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Authored by the Breathe Radon Free Team. Every claim is backed by a primary source. Full bibliography at /sources.
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