Radon Testing in Ottawa: Canada's Highest-Risk Major City
Ottawa homes test high for radon more often than homes in almost any other major Canadian city. In some surveys, close to 1 in 5 Ottawa-area homes sit above Health Canada’s 200 Bq/m³ guideline.
So if you own a home in Ottawa, testing isn’t a “nice to have.” It’s the single most useful thing you can do for your family’s air.
Here’s the honest part. We’re based in Guelph, about 5 hours west. We don’t drive to Ottawa for a single test. But you can still get a proper, lab-grade result, and we’ll show you exactly how.
The short version:
- Ottawa has some of the highest home radon levels of any big Canadian city
- The cause is local geology: Champlain Sea clay and granite bedrock rich in uranium
- Health Canada and the Canadian Cancer Society say every home should test once
- A DIY long-term kit costs $40 to $80. Our mailed 91-day monitoring service is $299
- For same-week, in-person testing, hire a local Ottawa C-NRPP pro (we’ll point you to the directory)
- New builds bought since February 2021 may have builder-paid mitigation through Tarion
Why Ottawa’s radon is so high
It comes down to what’s under the ground. Ottawa sits on some of the most radon-prone soil in the country.
Radon forms when uranium in soil and rock breaks down. The gas seeps up through cracks in a foundation and settles in the lowest lived-in level. More uranium in the ground means more radon in the basement.
Two things make Ottawa a hot spot:
- Champlain Sea sediments. Thousands of years ago, a shallow sea covered the region. It left behind thick clay and marine deposits. That soil traps and channels radon toward homes.
- Granite Canadian Shield bedrock. The rock across the Ottawa Valley carries more uranium than the sedimentary rock under most of southern Ontario.
Put those together and you get a lot of soil gas with nowhere to go but up.
This is why Ottawa keeps landing near the top of radon surveys. Health Canada’s Cross-Canada study found the Ottawa region among the highest for the share of homes above the guideline.
The map only takes you so far, though. Two houses next door to each other can read very differently. The only way to know your home is to test it.
Does a high-radon city mean I definitely have a problem?
No. It means your odds are higher, not certain. Even in Ottawa, most homes come back below the guideline.
But “most” isn’t “all.” When close to 1 in 5 homes tests high, that’s a real chance, not a rare fluke.
A few things push your odds up further:
- A finished basement where your family spends real time
- A basement bedroom, especially a child’s
- An older home with a stone or cracked foundation
- A home built tight for energy savings, which traps gas inside
Radon is the second-leading cause of lung cancer in Canada, after smoking.
How Ottawa homeowners can test (three real options)
You have three honest paths. We only sell one of them, and we’ll tell you when the others fit better.
| Option | Cost | Time | Best for |
|---|---|---|---|
| DIY long-term kit | $40 to $80 | 91+ days | Budget-first, patient homeowners |
| Our mailed 91-day service | $299 | 91+ days | A guided, documented long-term result |
| Local Ottawa C-NRPP pro | Varies | Days | Home sales, fast answers, in-person work |
Option 1: a DIY long-term kit
Buy an alpha-track kit online or from some Ontario public-health units. Place it in the lowest lived-in level for 91 days or more. Then mail it to the lab. One average number comes back.
This is a solid, cheap way to screen your home. The catch is the wait and the placement rules. Get the spot wrong and the result is off.
Option 2: our mailed 91-day monitoring
We ship you a device, walk you through placement, and read the data when it comes back. You get a written report you can keep or use for a claim. The price is $299 for the full 91-day window.
This suits Ottawa homeowners who want the long-term gold standard without guesswork. Learn more in our guide to long-term radon monitoring.
Option 3: hire a local Ottawa pro
If you’re buying or selling, or you want an answer in days, use a certified pro who lives near you. The C-NRPP public directory lists measurement pros by region.
We’d rather send you to a good local tester than pretend we can serve every corner of Ontario in person. That’s the honest call.
DIY kit vs hiring a pro: how to choose
Both work. The right pick depends on your timeline and why you’re testing.
| DIY long-term kit | Professional test | |
|---|---|---|
| Cost | $40 to $80 | $299 mailed, or local pro pricing |
| Time to result | 91+ days | 91 days, or days for a short pro test |
| Data | One average number | Full report, sometimes hour-by-hour |
| Placement help | You’re on your own | Guided or done for you |
| Good for a home sale? | No | Yes |
Go DIY when you’re not selling, you can wait a season, and you just want a first honest look. A $50 kit in the right spot beats no test at all.
Hire a pro when you’re in a real estate deal, you’re filing a Tarion claim, your DIY result landed near the line, or you want the placement and paperwork handled.
One caution for Ottawa. Because the city has real radon and real demand, some handymen advertise “radon service” without training. Always check a tester’s credential on the C-NRPP directory before you hire.
When to test in Ottawa
Test in the colder months if you can, roughly November through April.
Radon peaks in winter. The ground freezes, so soil gas pushes into your warm basement instead of venting outside. Closed windows keep it trapped. A summer test in the same home can read a third lower.
That seasonal swing is a big reason long-term monitoring wins. It spans the highs and the lows and gives you a true yearly average.
Other smart times to test:
- Right after you buy a home
- After you finish a basement or install a sump
- Two years after any mitigation system goes in
- Once every five years, even after a low reading
To learn what your number actually means, read our guide to radon levels.
New Ottawa builds: the Tarion path
Did you buy a new home from a builder in Ontario on or after February 1, 2021?
If so, your Tarion New Home Warranty may cover radon mitigation up to $50,000, paid by the builder, for a full 7-year term.
That coverage kicks in once a proper test shows radon at or above 200 Bq/m³. Your job is to test, document it, and file the claim.
Ottawa has plenty of new subdivisions built since 2021. Given the region’s high radon, this is one of the most valuable warranties many owners don’t know they hold. See our Tarion warranty guide for the eligibility checklist and claim steps.
What to do next
Radon is invisible and has no smell. In a city like Ottawa, guessing is the worst option.
Start with a test. If you want a guided long-term result mailed to your door, our 91-day monitoring service is $299. If you’d rather hire someone local for a quick in-person test, the C-NRPP directory has Ottawa pros ready.
Either way, the first step is the same. Measure the air your family breathes, then decide.
- Order a mailed 91-day radon test
- How radon testing actually works
- See where Ontario’s radon hot spots are
Frequently asked questions
Why does Ottawa have such high radon?
The local geology. Ottawa sits on Champlain Sea clay and granite Canadian Shield bedrock, both rich in uranium. As that uranium breaks down, it releases radon gas that seeps into homes. This is why Ottawa often tops big-city radon surveys in Canada.
Do you test homes in Ottawa?
Not in person. We’re based in Guelph, about 5 hours away, so we don’t drive to Ottawa for single tests. We do offer a mailed 91-day monitoring service for $299. For fast, in-person testing, we point Ottawa homeowners to certified local pros on the C-NRPP directory.
How much does radon testing cost in Ottawa?
A DIY long-term kit runs $40 to $80. Our mailed 91-day service is $299. A local pro’s short-term test price varies, so ask for a quote. For a home sale, in-person testing is usually worth the cost.
Is a short test good enough in Ottawa?
A short test is fine for a quick screen or a real estate deadline. But Ottawa’s big seasonal swings make a 91-day long-term test the more reliable basis for a mitigate-or-not decision.
My Ottawa test came back high. Is that an emergency?
No. Radon harms your health slowly, over years. A high reading means you should plan to fix it within a few months, not panic. If your home was built since February 2021, check whether Tarion covers the mitigation.
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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