A note before you read. This article provides general health and home-testing information for homeowners and tenants in Longueuil and the South Shore, drawn from publications of Health Canada, the Institut national de santé publique du Québec (INSPQ), the OACIQ, CARST, and the Canadian Cancer Society. It is not medical advice or legal advice. See full disclaimers at the bottom of the page.
Longueuil, on the South Shore of Montréal, sits on sedimentary bedrock similar to the Island of Montréal — mainly Paleozoic limestones and shales beneath a layer of glacial till overburden. Quebec's residential radon prevalence, per Health Canada's Cross-Canada Survey of Radon Concentrations in Homes (2012), sits at roughly the Canadian average — close to 7% of homes at 200 Bq/m³ or higher, with substantial regional variation.
Whether you live in Vieux-Longueuil, Saint-Hubert, Greenfield Park, LeMoyne, or elsewhere on the South Shore (Brossard, Saint-Lambert, Boucherville), radon testing is the baseline indoor-air-quality check that protects your household. The South Shore has many single-family homes with full basements used as bedrooms, home offices, and rental units — exactly where radon concentrates.
The essentials for Longueuil homeowners and tenants
- Health Canada residential guideline: 200 Bq/m³ (Health Canada — Radon). Quebec's prevalence sits at roughly the Canadian average.
- Test your Longueuil home with a 91-day long-term alpha-track test at the lowest lived-in level, during the heating season (October–April).
- Order a $89 long-term test kit →
- Quebec real estate is regulated by the OACIQ; the Civil Code's latent defect framework generally triggers disclosure of known elevated results.
Table of contents
- Why test Longueuil homes
- What the Quebec data shows
- How to test your Longueuil home
- Mitigation in Longueuil
- Real estate and OACIQ disclosure
- Tenants in Longueuil
- FAQ — Longueuil-specific questions
- Order your test kit
- Important disclaimers
- Sources and further reading
Why test Longueuil homes
Montréal's South Shore rests on the same sedimentary setting as the Island of Montréal. Three factors make testing essential:
- Geology. Uranium-bearing parent material is present locally and can produce radon beneath South Shore homes.
- Long heating season. Quebec winters mean months of continuous furnace operation, creating a strong stack effect that draws soil gas in through foundation cracks and slab penetrations.
- Housing stock. Longueuil and the South Shore have a large number of single-family homes and semi-detached houses with full basements — exactly where radon concentrates.
The INSPQ treats residential radon as a public-health priority across Quebec.
What the Quebec data shows
Health Canada's 2012 Cross-Canada Survey puts Quebec at roughly 7% of homes tested above the 200 Bq/m³ residential guideline, with substantial regional variation. The Greater Montréal area (including Longueuil and the South Shore) generally shows lower prevalence than the Estrie or Outaouais regions — but it remains significant at the level of an individual home.
The practical takeaway: provincial averages don't predict your home's level. Test the house you live in.
How to test your Longueuil home
Per Health Canada's published guidance (Guide for Radon Measurements in Residential Dwellings), the Canadian residential standard is a long-term test of at least 91 days using an alpha-track detector, deployed at the lowest lived-in level during the heating season (October–April).
For most Longueuil homes:
- Finished basement if it serves as a bedroom, office, gym, family room, or rental unit — that's where to test.
- Lowest sleeping level if the basement is unfinished.
- Ground floor only if the home has no basement.
Place the kit at breathing height (1 to 2 metres off the floor), away from drafts, exterior walls, and HVAC registers. Leave it in place for at least 91 days, then return it to the lab in the prepaid Canada Post envelope.
Order your $89 long-term test kit →
Mitigation in Longueuil
If your test exceeds 200 Bq/m³, the standard Canadian solution is active sub-slab depressurization (SSD). Typical cost in the Longueuil area: $2,500 to $4,500 for a standard SSD installation on a single-family home.
Always use a C-NRPP-certified mitigation professional. Verify on the C-NRPP directory, filtering by Quebec. The South Shore is well served by C-NRPP-certified Quebec contractors, many of whom work out of the Greater Montréal area.
For the full selection guide, see our guide How to Choose a Licensed Radon Mitigation Professional in Canada. After mitigation, run an independent post-mitigation test to confirm levels are below 200 Bq/m³.
Real estate and OACIQ disclosure
Quebec real estate is regulated by the OACIQ. The Seller's Declaration form asks sellers to disclose known material defects. Quebec's Civil Code latent defect (vices cachés) framework is more buyer-protective than the common-law doctrine in force in other provinces. A confirmed elevated radon test is generally the type of material information that the latent defect doctrine can trigger. Consult a Quebec notary or real estate lawyer for any specific transaction.
Tenants in Longueuil
Quebec's residential tenancy framework is administered by the Tribunal administratif du logement (TAL). The Civil Code generally requires landlords to deliver and maintain dwellings "in good habitable condition." Health Canada's guideline of 200 Bq/m³ informs the meaning of "habitability" in the radon context. See our guide Radon for Canadian Renters (2026).
FAQ — Longueuil-specific questions
Is radon a real concern in Longueuil? Yes — although the Greater Montréal area shows lower prevalence than the Estrie or Outaouais regions, South Shore homes can exceed the Health Canada guideline of 200 Bq/m³. Test your home.
What is the action level for radon in Longueuil? 200 Bq/m³ — Health Canada's residential guideline.
How do I test my Longueuil home? Use a 3-month (≥91 day) long-term alpha-track test from a C-NRPP-recognized lab, placed at the lowest lived-in level during the heating season. Cost: $89 all-in for a RadonTest.ca kit.
How much does radon mitigation cost in Longueuil? Typical cost: $2,500 to $4,500 for a standard sub-slab depressurization (SSD) system.
Do Quebec sellers have to disclose radon? Quebec's Civil Code latent defect framework and the OACIQ Seller's Declaration generally require disclosure of known material defects. Consult a Quebec notary or real estate lawyer.
Does the Tarion warranty cover radon mitigation for new homes in Longueuil? No — Tarion is the Ontario warranty. In Quebec, new-home warranties are administered by the Garantie de construction résidentielle (GCR).
Can I use the Lungs Matter grant in Longueuil? The Lungs Matter program offers up to $1,500 to eligible Canadian homeowners, which generally includes Quebec residents. Verify directly.
Should I retest after mitigation? Yes — Health Canada generally recommends retesting after mitigation and after major renovations.
What if my Longueuil landlord refuses to act? Document everything in writing and consider a recourse to the Tribunal administratif du logement (TAL).
Should South Shore semi-detached houses and duplexes be tested separately? Yes. Each regularly occupied unit of a semi-detached house, duplex, or triplex should have its own long-term test.
Order your test kit
Order your $89 all-in long-term test kit →
91-day long-term alpha-track test kit. C-NRPP-listed device. Analysis performed at Lex Scientific in Guelph, Ontario — Canadian lab, C-NRPP listed, ISO/IEC 17025 accredited by CALA. Tracked Canadian shipping both ways. PDF lab report delivered to your inbox.
Shipping across the entire South Shore including Longueuil, Saint-Hubert, Brossard, Saint-Lambert, Boucherville, and the surrounding municipalities.
Important disclaimers
Not medical, legal, or warranty advice. Consult qualified Quebec professionals for any specific decision.
Statistics and citations. Quebec prevalence figures are taken from Health Canada's 2012 Cross-Canada Survey and regional INSPQ publications. Figures reflect the sources as of May 2026.
Local data. Prevalence in the Greater Montréal area is generally modest, but home-to-home variability is large. Test your home.
Mitigation cost. The $2,500 to $4,500 range reflects typical Canadian prices in 2026. Actual prices vary.
Lungs Matter grant. Eligibility, grant amounts, and program availability may change. Verify directly at lung.ca before relying on the program.
No diagnosis or treatment claims. RadonTest.ca sells radon test kits. We do not diagnose, treat, or prevent any disease.
No warranty as to completeness. RadonTest.ca makes no warranty as to the completeness or accuracy of the information presented here and accepts no liability for decisions made in reliance on this article.
Sources & further reading
Quebec-specific
- INSPQ — Radon
- OACIQ
- Tribunal administratif du logement (TAL)
- Garantie de construction résidentielle (GCR)
Health Canada / national
- Health Canada — Radon
- Cross-Canada Survey (2012)
- Canadian Cancer Society — Radon
- Canadian Lung Association — Lungs Matter
- C-NRPP — Find a Professional
- CARST
- Take Action on Radon
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