A note before you read. This is general consumer information for Canadian homeowners, buyers, and builders, drawn from publicly available Health Canada, building-code, and Tarion 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. A radon "rough-in" in a new home is a code feature, not proof that your home is below the guideline — the only way to know your level is to test after you move in.
Key facts at a glance
- A brand-new home can have high radon too. Radon seeps up from the soil beneath any house, and newer, more airtight homes can actually trap it more readily. Age is no guarantee of a low level.
- A code "rough-in" is a capped pipe, not a working system. Since 2010 the National Building Code has required new homes to include a soil-gas barrier and a rough-in — a sealed, capped vertical pipe ready for a fan. On its own it is passive: it does not actively reduce radon, and it is not proof that your home is below 200 Bq/m³.
- Health Canada says to test after you move in. Testing after occupancy — ideally a long-term test over the first full heating season — is the only way to learn your new home's actual level.
- If the level is high, a fan converts the rough-in to an active system. A C-NRPP-certified professional adds and properly vents a fan, turning the passive pipe into an active soil-depressurization system — usually a faster, tidier job than retrofitting from scratch.
- In Ontario, the new-home warranty (administered by Tarion) may cover radon mitigation; most other provinces' warranties do not. Coverage is conditional and limited — see the warranty section below, and confirm details with Tarion.
- The rough-in is a head start, not a finish line. It means your home is ready to be fixed quickly if needed — not that it has been.
Can a brand-new home have high radon?
Yes. This is the single most important thing to understand about new construction: a new home is not automatically a low-radon home. Radon doesn't come from old materials, old wiring, or a tired foundation — it comes from the uranium that occurs naturally in the soil and rock beneath the house. As that uranium decays, it produces radon gas, which moves up through the ground and is drawn into the home through the foundation. A house built last month sits on the same soil as the house that was there before it, and that soil is the source.
In fact, newer homes can be more prone to elevated indoor radon, not less. Modern homes are built to be airtight and energy-efficient — tight building envelopes, better insulation, fewer drafts. That's excellent for heating bills, but it also means that once radon enters, there's less natural air exchange to dilute it, so it can accumulate to higher concentrations indoors. Tight construction plus the normal "stack effect" — warm air rising and escaping through the upper floors, which gently draws replacement air (and soil gas) in from below — can pull radon up out of the ground and hold it inside.
The Canadian data bears this out. Elevated radon has repeatedly turned up in newer housing:
- In a Health Canada survey of homes in the Halifax area, roughly 67% of newer homes tested above the guideline — a striking reminder that "new" does not mean "low." (Attributed to the Halifax-area survey reported by Health Canada; the figure reflects that particular high-radon geography and is not a national average.)
- In Alberta, research associated with the Evict Radon / University of Calgary program has found that newer homes averaged higher radon levels than older ones in the regions studied — the opposite of what many homeowners assume. (Attributed to Evict Radon / University of Calgary, based on long-term household testing.)
Both findings point the same way: building age tells you nothing reliable about your radon level. Two houses next door to each other — one new, one old — can read completely differently depending on soil, foundation, and ventilation. The only way to know is to measure your own home. For how levels vary across the country, see radon levels by province, and for what the numbers mean, see acceptable radon levels in Canada.
What a radon rough-in is (and isn't)
If your home is recent, it very likely has a radon rough-in built in — and it's easy to misread what that means.
What the code requires. Since 2010, the National Building Code of Canada has required new homes to include radon-control measures: a soil-gas barrier (a sealed membrane, typically heavy polyethylene, laid under the slab to slow gas entry) and a rough-in — a capped vertical pipe that runs from beneath the slab up through the house, ready for a fan to be connected later if it's ever needed. Some provinces and municipalities go further than the national baseline:
- Ontario strengthened its radon provisions in its 2024 building code.
- Quebec has required radon measures in new construction since June 2022.
- Alberta has had radon rough-in requirements in its building code, and municipalities such as Guelph and Hamilton have adopted enhanced local requirements.
What a rough-in actually does — and doesn't. Here is the part that trips up new-home owners. A rough-in is passive. It is, in effect, a pre-installed pipe — not a system. There is no fan running, so it is not actively pulling radon out from under your home. A capped, passive stack relies only on natural air movement and provides limited, unverified protection at best. Critically:
A radon rough-in does not prove your home is below 200 Bq/m³. It is a code feature that makes a future fix easier — not a measurement, and not a guarantee.
Think of it like a home wired for an alarm but with no alarm installed yet. The wiring is genuinely useful — it makes adding the real thing fast and clean — but it isn't doing the job on its own. For the full picture of how the codes handle radon across the country, see Canadian building codes and radon.
Why you still have to test
Because the rough-in is passive and unverified, the only way to know your new home's radon level is to test it — exactly like any other home. There is no shortcut, no certificate from the builder, and no code provision that substitutes for an actual measurement.
Health Canada's guidance for new construction is direct: test after you move in. A new home behaves differently once it's lived in — heating, ventilation, and the way the family uses the space all affect radon — so the meaningful reading is one taken during normal occupancy, ideally over the first full heating season after you take possession.
What to do with the result is the same as for any home:
- If your long-term result is at or above 200 Bq/m³, Health Canada recommends taking corrective action within one year — and sooner the higher the level. A reading in the hundreds well above the guideline warrants moving quickly; one just over the line still needs fixing, but you have a little more time to plan it well.
- If it's below 200 Bq/m³, no action is recommended — though no level is risk-free, so some households choose to reduce a moderate reading further.
The good news for new builds is the fix is usually straightforward. Because the rough-in is already in place, a C-NRPP-certified professional can complete an active system by adding and properly venting a fan to the existing pipe, turning the passive stack into an active soil-depressurization system. That's typically a faster, less invasive job than retrofitting an older home from scratch. For how the fix works, see how radon mitigation works in Canada, and for a step-by-step on a high result, see what to do if your radon level is above 200 Bq/m³.
New-home warranty & radon
If you're in a new build, it's worth knowing whether your warranty could help cover a fix — and the answer depends heavily on where you live.
Ontario. Ontario's statutory new-home warranty, administered by Tarion, may cover radon mitigation. For homes whose Agreement of Purchase and Sale (APS) was signed on or after February 1, 2021, the warranty can cover radon mitigation up to $50,000 within the seven-year major-structural-defect window, where a home's radon level exceeds the guideline and the claim meets Tarion's conditions. Coverage is not guaranteed — eligibility, limits, and timelines are determined solely by Tarion under its terms, so confirm the specifics with Tarion before relying on it.
Most other provinces. Outside Ontario, most new-home warranty programs do not cover radon mitigation. Programs in British Columbia, Alberta, Quebec, and elsewhere have their own coverage rules, and radon is generally not a covered item. Don't assume your province's warranty mirrors Ontario's — check your specific warranty documents.
For a province-by-province breakdown, see does your new-home warranty cover radon?, and for the Ontario specifics, see our Tarion radon warranty claim guide.
RadonTest.ca is an independent Canadian radon testing provider. It is not affiliated with, endorsed by, or licensed by the Tarion Warranty Corporation. "Tarion" is used here only to identify Ontario's statutory new-home warranty program. Coverage is not guaranteed; eligibility, coverage limits, and timelines are determined solely by Tarion under its terms. Always verify at tarion.com. This is general information, not legal or warranty advice.
When to test a new build
A new home deserves the same testing approach as any other, with a couple of timing notes specific to new construction.
- Run a long-term test of at least 91 days (three months). This is what Health Canada's 200 Bq/m³ guideline is written against, because radon swings hour to hour and season to season. A short-term snapshot can't tell you your home's true annual exposure. (For the difference, see short-term vs long-term radon tests.)
- Test over the first heating season after occupancy, ideally. Radon levels are typically highest in the colder months, when homes are closed up and the stack effect is strongest — so a test that spans the heating season after you move in gives the most representative picture. If you take possession in spring or summer, you can still test, but a heating-season test is the gold standard.
- Retest after major renovations. If you later finish a basement, change the foundation, add a sump, or carry out an energy retrofit (new windows, added insulation, air sealing), retest — those changes can shift your level. See how often to retest for radon.
One reassurance on timing: radon is a long-term, cumulative risk, not an acute one, so there's no need to panic if you can't start the moment you move in. The goal is simply to get a real, long-term number for your specific home and act on it if it's at or above the guideline.
Frequently asked questions
Do new homes have radon? Yes. Radon comes from the soil beneath any home, so a new house can have elevated radon just like an older one — and because new homes are built tight and energy-efficient, they can trap radon more readily once it enters. Building age is not a reliable indicator of your level; only a long-term test can tell you.
My new home has a radon pipe / rough-in — am I protected? Not necessarily. A rough-in is a passive capped pipe required by the building code; it does not actively reduce radon and is not proof your home is below 200 Bq/m³. It becomes a working ("active") system only when a fan is added. You still need to test, and if your level is high, a C-NRPP-certified professional activates the rough-in by fitting and venting a fan.
Are new homes lower-risk for radon than older ones? Not automatically. Some Canadian data points the other way: a Health Canada survey of the Halifax area found roughly 67% of newer homes above the guideline, and Evict Radon / University of Calgary research in Alberta has found newer homes averaging higher than older ones in the regions studied. The radon source is the soil, and tighter modern construction can hold more of it indoors. Test regardless of your home's age.
Does Tarion cover radon? In Ontario, the new-home warranty administered by Tarion may cover radon mitigation up to $50,000 within the seven-year window for homes whose Agreement of Purchase and Sale was signed on or after February 1, 2021, where the claim meets Tarion's conditions. Coverage is not guaranteed and the terms are set by Tarion — confirm with Tarion at tarion.com. RadonTest.ca is not affiliated with Tarion. Outside Ontario, most new-home warranties do not cover radon.
When should I test a new construction home? After you move in. Run a long-term test of at least 91 days, ideally over the first full heating season after occupancy, when radon levels tend to be highest. Retest after major renovations or energy retrofits, since those can change your level.
Does the building code mean my home is below the guideline? No. The code requires a soil-gas barrier and a passive rough-in — measures that make a future fix easier — but it does not measure or certify your radon level, and it does not guarantee you're below 200 Bq/m³. Code compliance and a low radon result are two different things; the only way to confirm your level is to test.
Do builders test for radon before handover? Generally no — testing isn't a standard part of new-home handover in most of Canada, and the building-code rough-in requirement doesn't include a post-occupancy test. That's why Health Canada advises homeowners to test themselves after moving in.
We're buying a new build — should radon come up in the purchase? It's worth raising. Even with a rough-in, the home's level is unknown until tested. If you're navigating a purchase, see radon in real estate: buying and selling in Canada for how testing fits into the process.
Test your new home — it's the only way to know
A radon rough-in is a genuine head start: it means your home is built to be fixed quickly if it ever needs to be. But it isn't a measurement, and it isn't a guarantee. The only way to know whether your new home is at, above, or comfortably below the 200 Bq/m³ guideline is a long-term test after you move in.
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 — Reducing radon levels in your home (test after moving in; corrective action at/above 200 Bq/m³ within one year, sooner the higher; activating a passive rough-in with a fan; C-NRPP), modified 2025-10-09. https://radontest.ca/links/hc-mitigation-guide
- Health Canada — Radon: Reduction Guide for Canadians (soil-gas barrier and rough-in; passive stack vs active system; levels of control; new-construction measures; Halifax-area survey of newer homes ~67% above the guideline), published Feb 2023, 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
- Tarion — Eight quick facts about radon (Ontario new-home warranty radon coverage; up to $50,000; seven-year window; Agreement of Purchase and Sale on/after February 1, 2021; verify with Tarion). https://www.tarion.com/media/eight-quick-facts-about-radon
- Evict Radon / 2024 Cross-Canada Radon Survey, University of Calgary (long-term household testing; Alberta-region finding that newer homes averaged higher radon levels than older homes). https://crosscanadaradon.ca/survey/
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. RadonTest.ca is not affiliated with, endorsed by, or licensed by the Tarion Warranty Corporation; "Tarion" is used only to identify Ontario's statutory new-home warranty program, and warranty coverage, eligibility, and limits are determined solely by Tarion under its terms — verify at tarion.com. A radon rough-in is a building-code feature, not a measurement or a guarantee that a home is below the guideline. Mitigation should be carried out by a C-NRPP-certified professional (directory at c-nrpp.ca/find-a-professional). Statistics attributed to Health Canada and the Evict Radon / University of Calgary study reflect the specific surveys and geographies cited and are not national averages; confirm time-sensitive details (code requirements, program availability, warranty terms) with the responsible body.