A note before you read. This is general consumer information for Canadian homeowners, buyers, sellers, and renters, drawn from publicly available Health Canada and C-NRPP sources. It is not medical, legal, or warranty advice. Radon results are reported against the Health Canada guideline of 200 Bq/m³; RadonTest.ca coordinates testing logistics and does not interpret individual results or provide health assessments.
See the radon gas map — measured results for every surveyed area, searchable by postal code.
Key facts at a glance
- Not having a basement does not mean not having radon. Radon comes from the soil, and any home in contact with the ground — slab-on-grade, crawl space, or a mobile/manufactured home — can have elevated levels. Health Canada's measurement guidance applies to all of them (Health Canada, Guide for radon measurements in homes, modified 2026).
- The gas enters the same way it enters a basement: through cracks and joints in a floor slab, around service pipes and support posts, through floor drains and sumps, and — in crawl spaces — straight up from exposed soil. "While higher radon levels are typical in basements and crawl spaces, elevated radon levels can be found throughout a home" (Health Canada, 2026).
- In a home with no basement you test the lowest lived-in level — usually the main floor. Health Canada directs you to test a "normal occupancy area," defined as a space someone uses more than four hours a day (Health Canada, 2026).
- You generally do not test an unoccupied crawl space. The test goes in the lowest level people actually live in, not in a crawl space nobody spends time in (Health Canada, 2026).
- About 17.8% of Canadian homes tested at or above 200 Bq/m³ in the 2024 Cross-Canada Radon Survey — up from about 6.9% in the previous survey — and single-detached houses were the most likely to be elevated (2024 Cross-Canada Radon Survey / Evict Radon, 2024).
- Radon is the leading cause of lung cancer in people who have never smoked and is estimated to cause about 16% of lung-cancer deaths in Canada — more than 3,000 a year (Health Canada, 2025). No radon level is risk-free; the 200 Bq/m³ guideline is the level at which Health Canada recommends acting.
- Fixes are foundation-specific but effective: sub-slab depressurization for slab homes, active sub-membrane depressurization for crawl spaces, both able to cut radon by more than 80% (Health Canada, Reduction Guide for Canadians, modified 2025).
"No basement, no radon" is one of the most common myths
If your home sits on a concrete slab, over a crawl space, or is a mobile or manufactured home, it's easy to assume radon is a basement problem that doesn't apply to you. It's an understandable assumption, and it's wrong.
Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil and rock. It seeps out of the ground everywhere in Canada and gets indoors wherever a building meets the soil. A basement simply happens to be the part of a house most surrounded by earth, which is why basements often read highest — but the source is the ground beneath the whole footprint of your home, and a slab, a crawl-space floor, or the underside of a manufactured home is in just as much contact with that ground as a basement wall is. Health Canada's measurement guide, which covers low-rise residential buildings of all kinds, puts it plainly: "while higher radon levels are typical in basements and crawl spaces, elevated radon levels can be found throughout a home." The absence of a basement removes neither the source nor the pathway.
The national data backs this up. In the 2024 Cross-Canada Radon Survey, about 17.8% of homes tested at or above the 200 Bq/m³ guideline — roughly one in five, and up sharply from about 6.9% in the previous cross-Canada survey. Notably, the survey found that single-detached houses were more likely to be elevated than semi-detached or row houses — the very category that includes most slab, crawl-space, and rural manufactured homes. If anything, "no basement" homes are over-represented in the housing types that test high, not exempt from them.
How radon gets into a slab-on-grade or crawl-space home
The mechanism is the same one that pulls radon into any basement, and it has two parts: entry points and pressure.
The entry points. In a slab-on-grade home, radon rises from the soil and finds its way in through cracks and control joints in the concrete slab, the perimeter joint where the slab meets the foundation wall, gaps around plumbing and service pipes, spaces around support posts, and floor drains or sumps. Health Canada lists these same routes — "construction joints, gaps around service pipes, support posts, floor drains, sumps, or cracks in foundation walls and floor slabs" — and adds that radon "will also move through the foundation" itself. A crawl-space home adds the most direct pathway of all: exposed soil. Where a crawl space has a bare-earth or gravel floor, there is essentially nothing between the soil gas and the space under your floor — Health Canada specifically identifies "exposed soil or rock in crawlspaces" as an entry route — and the gas then moves up into the living area around ducts, pipes, wiring penetrations, and gaps in the subfloor.
The pressure — the "stack effect." Entry points alone don't move gas; a pressure difference does. Warm air inside a heated home rises and escapes through the upper levels, lowering the air pressure at the bottom of the house relative to the soil. That slight vacuum actively draws soil gas — radon included — in through every crack and penetration near the ground. This stack effect is strongest in winter, when the indoor–outdoor temperature difference is largest and homes are sealed up, which is why readings are generally highest over the heating season. It operates in a slab or crawl-space home exactly as it does in one with a basement: having no basement doesn't switch off the physics, it just changes which surface the gas comes through.
For a fuller picture of why below-grade and ground-contact spaces tend to concentrate radon, see our guide to radon in basements in Canada — the same principles drive levels in a slab or crawl-space home.
Mobile and manufactured homes: skirting, the "belly," and service penetrations
Mobile and manufactured homes deserve their own note, because their construction creates a radon pathway people rarely think about.
Most manufactured homes sit above the ground on piers, blocks, or a foundation, with the perimeter closed in by skirting. That skirting turns the space beneath the home into an enclosed, crawl-space-like cavity sitting directly over soil. If soil gas accumulates there, it has a ready path upward through the many penetrations in the home's floor — the plumbing, electrical, and duct openings that pass through the underbelly (the sealed membrane, sometimes called the "belly wrap," under the floor). Any tears or gaps in that underbelly, and any un-sealed penetrations, let radon-laden air from below move into the living space, driven by the same stack-effect pressure described above.
In practice this means a skirted manufactured home behaves, for radon purposes, much like a crawl-space home: the enclosed space under the floor can accumulate soil gas, and that gas can be drawn up into the rooms above. Ventilating that under-home space can help, but it isn't a substitute for testing — ventilation choices also involve freeze protection for plumbing and other trade-offs, so it's not a simple "just add vents" fix, and it doesn't tell you your actual radon level. Because you can't predict a manufactured home's radon level from its design, the only reliable answer is a long-term test inside the home, exactly as for any other dwelling.
Health Canada's published guides don't single out manufactured homes with a separate protocol, so treat them under the general guidance: test the lowest lived-in level, and if a fix is needed, have a certified professional assess the specific structure. The under-floor cavity is a real radon pathway, but one a qualified mitigator handles with well-established crawl-space techniques.
Exactly how and where to test when there's no basement
This is the part that trips people up, and the good news is that it's simpler than it sounds: the rule doesn't change just because you have no basement — you still test the lowest level of your home that you actually live in.
Test the lowest lived-in level. Health Canada directs you to place the detector in "a normal occupancy area of the lowest lived-in level of the home," where a normal occupancy area is "any space in which an individual spends more than 4 hours per day." In a home with no basement, the lowest lived-in level is almost always the main floor — so that's where the test goes.
Pick a room used at least four hours a day. A bedroom, living room, family room, or home office is ideal. Avoid the kitchen, bathrooms, and laundry room, whose extra ventilation and humidity don't reflect the air the rest of the home breathes.
Place it in the breathing zone. Health Canada defines the breathing zone as roughly 0.3 m to 2.5 m from the floor, and suggests a shelf, end table, or dresser as an appropriate spot (a device may also be suspended from the ceiling). Keep it out in the open with access to the room's main air space, away from windows, exterior doors, drafts, vents, direct sun, and heat sources — and out of the reach of children and pets. Our step-by-step guide on where to place your radon test kit walks through the clearances and the do's and don'ts.
Run it long, and don't change your habits. Use a long-term test — at least 91 days, and Health Canada recommends testing over a period of 3 to 12 months to estimate your true annual average, ideally spanning the heating season. Health Canada also notes that "residents should not alter their lifestyle during a long-term radon test," so live normally and leave the detector undisturbed. A quick, short-term test swings too much day to day to base a decision on — see short-term vs long-term radon testing in Canada for why, and when radon testing season is in Canada for timing.
Should you test the crawl space itself?
Generally, no. Health Canada's guidance is to measure in the lowest lived-in level — the space where people spend time — not in an unoccupied crawl space. A crawl space is not a normal occupancy area; nobody breathes its air for four-plus hours a day, so a reading taken down there wouldn't represent your household's actual exposure (and would likely be alarmingly high without telling you what's happening in the rooms above). What matters for your health, and for the decision to mitigate, is the radon level in the main-floor rooms you live in. So place the test on the main floor, above the crawl space, following the placement rules above.
(There is a narrow exception in Health Canada's definition of "normal occupancy area": a space that isn't used every day but averages more than four hours a day of use over the year, or a space "that may become occupied soon" — for example, a basement being renovated into a bedroom — can count as a normal occupancy area. A bare, unfinished crawl space you never occupy does not.)
When you're ready, you can order a long-term kit here and place it on your main floor.
How you read the result — the number is the same either way
Whatever foundation you have, the result is judged against one number: Health Canada's guideline of 200 Bq/m³, as an annual average. If your long-term result comes back at or above 200 Bq/m³, Health Canada recommends taking corrective action within one year — and the higher the reading, the sooner you should act. If it's below the guideline, that's reassuring, but no radon level is considered risk-free — the guideline is an action threshold, not a line between "acceptable" and "harmful." Our walkthrough on how to read your radon test results explains what the number means, and what to do if your radon level is above 200 Bq/m³ covers the next steps. A slab or crawl-space home is read against exactly the same guideline as a home with a basement.
Fixing radon without a basement: sub-slab vs. sub-membrane systems
Here is the genuinely encouraging part: homes without basements are very fixable, and the methods are well established. Health Canada notes that radon in most homes can be reduced by more than 80% for roughly the cost of other common home repairs, and that the technology to do it is highly effective in Canada. The right technique depends on your foundation.
Slab-on-grade → sub-slab depressurization. For a home on a concrete slab, the standard fix is sub-slab depressurization (also called active soil depressurization) — which Health Canada calls "the most effective and reliable radon reduction technique" and "the most common method used by C-NRPP certified professionals." A pipe is installed through the slab, and a continuously running fan draws soil gas from beneath the foundation and vents it outdoors above the roofline, where it disperses harmlessly. This also reverses the pressure difference that was pulling radon in, so the gas is captured before it ever reaches your rooms.
Crawl space → active sub-membrane depressurization. Where the "floor" is a crawl space over soil, the equivalent fix is active sub-membrane depressurization. As Health Canada describes it, this "involves laying a thick plastic sheet (often a polyethylene membrane) over the soil, sealing the air-tight membrane to the foundation walls and placing a pipe with fan through it to draw the radon from under the plastic sheet and vent it to the outdoors." In effect, it seals the exposed soil under a membrane and continuously vacuums the radon out from underneath before it can enter the home. Careful sealing — especially around the pipe where it passes through the membrane — is what makes it work.
Mobile/manufactured homes. A skirted manufactured home over soil is typically addressed with the crawl-space approach — a sealed membrane over the ground beneath the home and an active vent system — adapted to the home's specific under-floor construction. Because the underbelly, piers, and skirting vary from home to home, this is a case where a professional assessment of the actual structure matters most.
A word on ventilation-only approaches. Increasing a home's mechanical ventilation — for example with a heat recovery ventilator (HRV) — is listed by Health Canada as one way to help lower radon, and it can play a supporting role. But ventilation typically produces smaller, less reliable reductions than active soil depressurization, and it isn't a substitute for a sub-slab or sub-membrane system where levels are well above the guideline.
Whichever applies, the work should be done by a C-NRPP-certified radon mitigation professional, who will diagnose your specific foundation and design a system for it. For the full picture of how these systems are designed and installed, see how radon mitigation works in Canada.
Why this matters most in the Prairies and rural Canada
There's a reason this topic isn't academic. The home types with no basement — slab-on-grade builds and manufactured homes — are especially common in the Prairies and in rural areas, precisely the regions where radon prevalence is highest. The 2024 Cross-Canada Radon Survey identified Prairie Canada, Atlantic Canada, the North, and the British Columbia Interior as areas where high indoor radon levels are more prevalent, and research from the University of Calgary's Evict Radon program has described the Prairie population as among the most radon-exposed on Earth. Put those facts together — more slab and manufactured homes, in the highest-radon regions — and the "no basement, so I'm fine" assumption becomes actively risky in exactly the places it's most often made.
The reassuring flip side is that these homes are testable and fixable like any other. A single long-term detector on the main floor tells you where you stand; a foundation-appropriate mitigation system brings an elevated level back down. For a region-by-region view, see radon levels by province: what the Canadian data shows, and for the framework behind all of this, Health Canada radon testing guidance.
Frequently asked questions
Can a house without a basement have radon? Yes. Radon comes from the soil, and any home in contact with the ground — slab-on-grade, crawl space, or manufactured home — can have elevated levels. Health Canada's measurement guidance applies to all home types and states that although basements and crawl spaces are typically highest, "elevated radon levels can be found throughout a home." Not having a basement is never a reason to skip testing.
Where do I put a radon test if I don't have a basement? On the lowest level you actually live in, which for a home with no basement is usually the main floor. Health Canada directs you to test a "normal occupancy area" — a room used more than four hours a day — with the detector in the breathing zone, roughly 0.3–2.5 m off the floor on a shelf or table, away from drafts, vents, windows, and heat. Leave it undisturbed for at least 91 days.
Should I test the crawl space itself? Generally no. Health Canada's guidance is to measure in the lowest lived-in level — where people spend time — not in an unoccupied crawl space, which isn't a normal occupancy area. A reading down there wouldn't reflect the air your household actually breathes. Place the test in the main-floor rooms above the crawl space instead.
Do slab-on-grade homes get radon? Yes. A slab sits directly on the soil, and radon enters through cracks and joints in the slab, gaps around pipes and support posts, and floor drains — the same entry routes Health Canada lists for any foundation — then gets pulled indoors by the stack effect just as in a home with a basement.
Do mobile or manufactured homes need radon testing? Yes. A skirted manufactured home encloses a crawl-space-like cavity over soil, and radon can move from it up through plumbing, wiring, and duct penetrations in the floor. You can't tell a manufactured home's radon level from its design, so a long-term test inside the home is the only way to know.
How do you fix radon in a home without a basement? The fix matches the foundation. Slab-on-grade homes use sub-slab depressurization — a pipe and continuous fan that draw soil gas from under the slab and vent it outdoors — which Health Canada calls the most effective and reliable technique. Crawl-space and skirted manufactured homes use active sub-membrane depressurization, sealing a membrane over the exposed soil and venting the gas from beneath it. Both can reduce radon by more than 80% and should be installed by a C-NRPP-certified mitigation professional.
Does the 200 Bq/m³ guideline apply to my slab or crawl-space home? Yes — it applies to all homes regardless of foundation. If your long-term annual-average result is at or above 200 Bq/m³, Health Canada recommends fixing it within a year, sooner the higher the level. Because no radon level is risk-free, the guideline is an action threshold, not a guarantee of safety below it.
Test the home you have — basement or not
If your home sits on a slab, over a crawl space, or up on skirting, radon is just as much your concern as your neighbour's with a basement — the gas comes from the same soil, enters through the same kinds of gaps, and is pulled in by the same winter pressure. The only difference is which surface it comes through, and where you place the test: the lowest level you live on, usually the main floor.
A single long-term detector answers the question for good, and if a fix is needed, the foundation-specific systems above are well proven and effective.
Order your RadonTest.ca kit → — lab analysis by a C-NRPP-certified laboratory (with an all-in-Canada analysis option), tracked shipping both ways, and your result delivered with clear Health Canada context.
Sources
- Health Canada — Guide for radon measurements in homes (guide covers low-rise residential buildings and units in multi-unit buildings; entry points include construction joints, gaps around service pipes, support posts, floor drains, sumps, cracks in foundation walls and floor slabs, and radon movement through the foundation; "while higher radon levels are typical in basements and crawl spaces, elevated radon levels can be found throughout a home"; "exposed soil or rock in crawlspaces" as an entry route; test a "normal occupancy area of the lowest lived-in level," defined as a space used more than 4 hours per day; breathing zone of about 0.3–2.5 m from the floor; shelf/end table/dresser or suspended from ceiling; test over 3–12 months, minimum 91 days; do not alter lifestyle during the test), modified 2026-05-22. https://www.canada.ca/en/health-canada/services/publications/health-risks-safety/guide-radon-measurements-residential-dwellings.html
- Health Canada — Radon – Reduction Guide for Canadians (sub-slab depressurization is "the most effective and reliable radon reduction technique" and "the most common method used by C-NRPP certified professionals"; crawl spaces use active sub-membrane depressurization with a polyethylene membrane sealed to the foundation walls and a pipe-and-fan vented outdoors; radon in most homes can be reduced by more than 80%; increasing mechanical ventilation, e.g. an HRV, as a supporting option; use a certified mitigation professional), modified 2025-09-24. https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radiation/radon-reduction-guide-canadians-health-canada.html
- Health Canada — Radon guideline (guideline of 200 Bq/m³ annual average; take corrective action within one year if at or above the guideline, sooner the higher the level; no radon level is risk-free), accessed July 2026. https://www.canada.ca/en/health-canada/services/health-risks-safety/radiation/radon/government-canada-radon-guideline.html
- Health Canada — Radon: What you need to know (radon is a leading cause of lung cancer; about 16% of lung-cancer deaths in Canada — more than 3,000 per year — are attributed to radon; no risk-free level), 2025 edition. https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radon-what-you-need-to-know.html
- 2024 Cross-Canada Radon Survey / Evict Radon (University of Calgary) — Cross-Canada Radon Survey (about 17.8% of homes at or above 200 Bq/m³, up from about 6.9% in the previous survey; single-detached houses more likely to be elevated than semi-detached or row houses; higher prevalence in Prairie Canada, Atlantic Canada, the North, and the BC Interior), 2024. https://crosscanadaradon.ca/survey/
- C-NRPP (Canadian National Radon Proficiency Program) — certification of radon measurement devices, laboratories, and mitigation professionals. https://c-nrpp.ca/
The estimate that the Prairie population is among the most radon-exposed on Earth is attributed to the University of Calgary's Evict Radon research program, not to Health Canada. The 17.8% and 6.9% figures are from the Cross-Canada Radon Survey (2024) and its predecessor, reported by Evict Radon / the University of Calgary. Lab analysis is performed independently by a C-NRPP-certified laboratory; results are reported against the Health Canada guideline of 200 Bq/m³. RadonTest.ca coordinates kit logistics and sample submission only — it does not interpret or modify lab results and does not provide medical, legal, or warranty advice. Information attributed to Health Canada, the Cross-Canada Radon Survey, and C-NRPP is summarized from the public sources listed above; confirm time-sensitive details with the responsible body.