Radon is a colourless, odourless radioactive gas produced as uranium in soil and rock breaks down. It seeps up into homes through foundation cracks, sumps, floor drains, and gaps around pipes, and collects in the lowest occupied levels, usually the basement. Any home can have elevated radon regardless of age, location, or how new or tight it is, the only way to know a specific house is to test it.
$30 to $60 long-term test; ~$2,500 to $3,500 to mitigate if highAddress soonInteriorStructure
The quick answer
Radon is an invisible, odourless gas that seeps up from the soil into basements and is Canada's leading cause of lung cancer after smoking, and any home can have it regardless of age. The only way to know is a test: a long-term kit is about $30 to $60. Health Canada says act above 200 Bq/m³, and the fix (a vent fan) is routine at ~$2,500 to $3,500, so a high reading is a negotiation, not a dealbreaker.
You are reading the radon gas page. Type the year the house was built and I will tell you what else tends to be true at that age, what it costs, and what to ask. One number, ten seconds.
Free. No account. Educational and impartial, not a home inspection.
Why it matters
Radon is the leading cause of lung cancer in Canada after smoking (Health Canada). It's also one of the few serious home hazards you can't see, smell, or infer from photos, and one of the cheapest to fix once you know. Health Canada's guideline is to take action above 200 Bq/m³. A high reading isn't a reason to walk away; it's a reason to test, negotiate, and mitigate.
How to spot it
You can't, it has no signs you can see in a listing. What raises the odds worth flagging: a finished basement people spend time in, slab-on-grade construction, sump pits and unsealed floor drains, and homes in areas with known elevated radon (much of Canada has pockets). The reliable check is a long-term test (three months or more); a short-term test can screen quickly and is often used as a condition of purchase.
What it costs
A do-it-yourself long-term test kit runs about $30 to $60; a professional measurement more. If a home tests high, a certified mitigation system (sub-slab depressurization, essentially a sealed pipe and fan that vents the gas outside) typically costs $2,500 to $3,500 in Canada and reliably brings levels down.
What to do
Address soon. If the home has a recent long-term radon result, ask for it; if not, you can make a radon test a condition and use the result to negotiate the mitigation cost. Hire a C-NRPP-certified professional for testing or mitigation. Mitigation is routine and effective, so a high reading is a price negotiation, not a dealbreaker.
Education and triage, not a home inspection. Casaroo can't measure radon from photos, no tool can. We flag homes and features where a test is worth doing; a C-NRPP measurement is the only thing that confirms a level. We flag; we don't certify.
Common questions
Can Casaroo or an inspector tell me if a house has radon?
No, and neither can anyone else from photos or a walkthrough. Radon has no visible signs. Only a test measures it, $30 to $60 for a long-term do-it-yourself kit, and a long-term test of three months or more is the reliable one.
Is a high radon reading a dealbreaker?
No. Mitigation is routine and effective, typically $2,500 to $3,500 for a sub-slab depressurization system, and it reliably brings levels down. A high reading is a price negotiation, not a reason to walk.
Can I make a radon test a condition of my offer?
Yes, and short-term tests are often used exactly this way because they screen quickly. If the seller has a recent long-term result, ask for it. If not, the test result gives you a number to negotiate the mitigation cost with.
Are newer homes safe from radon?
No. Any home can have elevated radon regardless of age, location, or how tight it is. That is why testing is the only answer, and why a new build is not a reason to skip it.
The 200 Bq/m³ figure is Health Canada's action guideline; testing and mitigation costs vary by home and region. Confirm with a C-NRPP professional. Casaroo flags, it does not inspect.
Last reviewed 2026-06-29.
This guide is general education, not a home inspection and not advice for your specific property. Always
consult the appropriate licensed professional, and get a licensed home inspection before you remove conditions
or buy. Cost ranges are 2026 estimates that vary by region, size, and access; confirm specifics with a
qualified professional.