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.
$30–60 long-term test; ~$2,500–3,500 to mitigate if highAddress soonInteriorStructure
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 $30–60; 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 $2,500–3,500 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
What is Radon gas?
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.
Why does it matter for home buyers?
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 can I 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.
How much does it cost to fix?
A do-it-yourself long-term test kit runs about $30–60; 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 $2,500–3,500 in Canada and reliably brings levels down.
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.