Radon in Hamilton (2026): The Municipal Radon Program and What Hamilton Homeowners Should Do

Flat-vector map of Canada with a coral red pin marking Hamilton, Ontario, alongside a circular badge showing 8% — Ontario's provincial share of homes above the Health Canada radon guideline

A note before you read. This article is general health and home-testing information for Hamilton homeowners, builders, and real estate professionals, drawn from Health Canada, the City of Hamilton, Cancer Care Ontario, Tarion, and the Canadian Cancer Society. It is not medical advice and is not legal or building-code advice. See full disclaimers at the bottom.

If you live in Hamilton — or you're building, buying, or selling a new home in Hamilton — there's something distinctive you need to know about radon: Hamilton has its own municipal radon construction program that goes beyond the Ontario Building Code. For new residential building permits applied for after November 16, 2020, Hamilton requires builders to choose one of three radon construction options, with mandatory radon testing for some of those options and mandatory active mitigation if test results exceed 200 Bq/m³. This puts Hamilton in a small group of Canadian municipalities (alongside Guelph, Kingston, and Niagara Region) with municipal radon programs that exceed provincial code minimums.

For existing Hamilton homeowners, the broader Ontario context applies: roughly 8% of Ontario homes test above the 200 Bq/m³ Health Canada guideline (more in some Ontario regions), and Hamilton's specific geology and housing stock produce variability worth knowing about. Combined with Ontario's Tarion warranty (up to $50,000 of radon mitigation for qualifying new builds), Hamilton has one of the most layered radon regulatory and protection frameworks in Canada.

This guide walks through Hamilton's municipal program, the broader radon picture for Hamilton homeowners, and the practical step-by-step from "I want to know" to "result in hand."

TL;DR for Hamilton homeowners and builders

  • Hamilton has a mandatory municipal radon construction program for new low-rise residential buildings (permits applied for after November 16, 2020). Three options: (1) Ontario Building Code rough-in plus soil-gas mitigation, (2) passive radon venting system, (3) full active sub-slab depressurization at construction.
  • Mandatory long-term radon testing applies depending on the option chosen — minimum 91 days during the winter heating season, results submitted to the City of Hamilton.
  • If post-construction test results exceed 200 Bq/m³, the property owner is required to install an active sub-slab depressurization system.
  • Ontario new-build owners may also have Tarion warranty coverage of up to $50,000 for radon mitigation on top of municipal requirements.
  • For existing Hamilton homeowners, the only way to know your home's level is to test. Order a $89 long-term radon test kit →

Table of contents

  1. Hamilton's municipal radon construction program — the three options
  2. What the published Hamilton/Ontario radon data shows
  3. Why Hamilton radon varies — geology, climate, and construction
  4. What to do as a Hamilton homeowner
  5. Hamilton + Tarion warranty for new-build owners
  6. Local Hamilton and Ontario resources
  7. FAQ — Hamilton-specific questions
  8. Disclaimers
  9. Sources

Hamilton's municipal radon construction program — the three options

Hamilton is one of a small number of Canadian municipalities that has chosen to go beyond the provincial Ontario Building Code on radon, with a dedicated municipal program for new low-rise residential construction. The program applies to new building permits applied for after November 16, 2020 and gives builders three compliance options.

Option 1: Ontario Building Code rough-in plus standard soil-gas mitigation measures. The minimum compliance path: capped vent pipe rough-in through the slab, soil gas barrier, sealed slab perimeter and penetrations, sealed sump cover, and other OBC 9.13.4 features.

Option 2: Install a passive radon venting system. Goes beyond the OBC minimum — the vent pipe is extended through the building envelope and terminated above the roof, using natural thermal stack effect to draw soil gas out without an active fan. National Research Council field studies have measured radon reductions of approximately 40–90% from passive stacks alone.

Option 3: Install a full active sub-slab depressurization system at construction. Includes a continuous-duty in-line radon fan. The most reliable approach for reducing radon — typical reductions of up to 95% per CARST and CREA published guidance.

Depending on the option chosen, mandatory post-construction radon testing applies. All required radon testing must be:

  • A long-term test (minimum 91 days)
  • Completed during the winter heating season (October to April)
  • Submitted to the City of Hamilton

If post-construction test results exceed 200 Bq/m³, the property owner is required to install an active sub-slab depressurization system. This is one of the few Canadian municipal frameworks with a mandatory test-and-mitigate cycle for new construction.

Source: City of Hamilton — Residential Construction Requirements for Radon Gas Mitigation

For builders, real estate lawyers, and homeowners navigating the program for a specific build, always verify current requirements directly with the City of Hamilton's Building Division before relying on this article.

Order a $89 long-term radon test kit →

What the published Hamilton/Ontario radon data shows

Hamilton-specific radon survey data is more limited than for some other Canadian cities, but the broader Ontario context is well-published:

  • Ontario provincial average (2012 Cross-Canada Survey): about 8% of homes above the 200 Bq/m³ guideline (Health Canada).
  • More recent Ontario testing has found about 25% of homes above the WHO recommendation of 100 Bq/m³, with about 8% above the Health Canada 200 Bq/m³ guideline.
  • Cancer Care Ontario notes that radon risk varies significantly across Ontario, with some Ontario regions in the higher-risk category.
  • Hamilton's geology — sitting on the Niagara Escarpment between the Lake Ontario lowland and the Carolinian zone — produces variable radon profiles across the city.

The takeaway: while Hamilton is not as high-radon as Calgary or Winnipeg, it is not a low-radon city in absolute terms. Combined with Hamilton's municipal program (which exists precisely because radon was identified as a meaningful local issue), the case for testing in Hamilton is strong — for both new-build owners navigating the program and existing-home owners outside it.

Order a $89 long-term radon test kit →

Why Hamilton radon varies — geology, climate, and construction

Three factors influence Hamilton's residential radon profile:

1. Geology. Hamilton sits on a varied geological setting — the Niagara Escarpment runs through the city, with different bedrock and soil types above and below the escarpment. Areas underlain by varying levels of uranium-bearing rock and glacial soils show different background radon. This means radon levels can vary substantially across Hamilton neighbourhoods depending on local geology — Stoney Creek, Ancaster, Dundas, and the lower city can all have meaningfully different profiles.

2. Climate. Hamilton has a typical Southern Ontario heating season — October through April — with cold winter temperatures that lead to homes being sealed against the weather. Furnaces and HVAC systems run regularly, and the natural "stack effect" actively pulls soil gas into basements.

3. Building construction. Hamilton has a mix of older industrial-era housing (Hamilton Centre, North End), suburban single-family construction (Stoney Creek, Ancaster, Glanbrook), and rural acreage in the upper city. Older homes typically lack any radon construction features; newer homes built post-November 2020 fall under the municipal program described above; mid-era homes (1990s-2020) fall under provincial Ontario Building Code minimums.

The combination — variable Niagara Escarpment geology + Southern Ontario heating season + mixed-era housing stock — is why Hamilton chose to implement a municipal radon program beyond OBC minimums, and why every Hamilton home is worth testing individually.

What to do as a Hamilton homeowner

Step-by-step:

Step 1: Test (long-term, 91+ days). Health Canada's recommended test for a homeowner mitigation decision is a long-term alpha-track lab test, deployed for at least 91 days during the heating season (October–April in Hamilton), in the lowest lived-in level of your home. If you're a new Hamilton home owner subject to the municipal program, your post-construction testing must comply with City of Hamilton requirements. For most testing scenarios, the test costs $89 all-in with RadonTest.ca — kit, tracked outbound, prepaid tracked Canada Post return label, and analysis at Lex Scientific in Guelph, Ontario (a C-NRPP-listed Canadian lab).

Step 2: Read your result. Below 200 Bq/m³, no mitigation is required (Health Canada recommends retesting every 5 years). Above 200 Bq/m³, mitigation is recommended — and for new Hamilton homes subject to the municipal program, mandatory active sub-slab depressurization installation applies. See our How to Read Your Radon Test Results and What to Do If Your Radon Level Is Above 200 Bq/m³ guides.

Step 3: Mitigate, if needed. A C-NRPP-certified mitigation contractor installs a sub-slab depressurization system at a typical Ontario cost of $2,500–$4,500. These systems typically reduce radon by up to 95% (Health Canada cites reductions of more than 80%; CARST cites up to 95%). Find a Hamilton-area C-NRPP-certified mitigator via the C-NRPP Find a Professional tool.

Step 4: Apply for Tarion warranty coverage (if applicable) AND/OR the Lungs Matter grant. See the Tarion section below. The Canadian Lung Association's Lungs Matter program offers up to $1,500 for eligible Canadians.

Step 5: Verify. Once mitigation is complete, run an independent post-mitigation test to confirm levels are below 200 Bq/m³.

Order your Hamilton kit — $89 →

Hamilton + Tarion warranty for new-build owners

Hamilton is in Ontario, so Tarion's statutory new-home warranty radon coverage applies on top of the municipal program. For Agreement of Purchase and Sale signed on or after February 1, 2021, and homes within the 7-year warranty window, Tarion covers up to $50,000 of radon mitigation if a qualifying long-term test (≥3 months) shows levels above 200 Bq/m³.

This means new Hamilton homeowners have two layers of protection:

  1. Municipal layer (post-November 2020 builds): builder must follow one of three radon construction options, with possible mandatory testing and mandatory mitigation if test fails.
  2. Provincial Tarion layer (post–February 2021 APS): builder warranty covers up to $50,000 of mitigation work if a qualifying test shows elevated radon.

The two layers work together. The municipal program ensures appropriate radon-aware construction; the Tarion warranty covers mitigation costs if the construction wasn't enough. For new Hamilton home owners, both layers should be understood — see our full Tarion radon warranty claim guide.

Note: Meeting Tarion test-type criteria is one of several conditions for a Tarion claim. Full requirements include the home being within the 7-year window, the result above 200 Bq/m³, testing in the basement, and proper filing through Tarion's process.

Local Hamilton and Ontario resources

Note on Ontario building code. New-build Hamilton homes are subject to both the 2024 Ontario Building Code (province-wide radon rough-in requirement) and Hamilton's municipal program described above. The Hamilton municipal program is more stringent than the OBC minimum.

Note on Ontario real estate disclosure. Ontario uses OREA's Form 220 (SPIS), which is voluntary but, once completed, requires truthful answers. Independent of the SPIS, the latent-defect doctrine applies under common-law principles, and a known elevated radon reading is generally treated as a material defect requiring disclosure. See our Real Estate Radon Guide.

FAQ — Hamilton-specific questions

Does Hamilton have a mandatory radon program for new construction? Yes. For new low-rise residential building permits applied for after November 16, 2020, builders must follow one of three radon construction options, with mandatory post-construction testing for some options and mandatory active sub-slab depressurization if testing exceeds 200 Bq/m³. Verify current rules directly with the City of Hamilton's Residential Construction Requirements page.

What are the three radon options in Hamilton's program? (1) Ontario Building Code rough-in plus soil-gas mitigation, (2) passive radon venting system, (3) full active sub-slab depressurization at construction. See the municipal program section above.

Is my existing (pre-2020) Hamilton home covered by the municipal program? No. The municipal program applies to permits applied for after November 16, 2020. For older Hamilton homes, the only way to know your radon level is to test it. Order a $89 kit →

Are some Hamilton neighbourhoods worse than others? Hamilton's geology varies — homes on the Niagara Escarpment, above the escarpment (Mountain), or below it in the lower city can have different background radon. Stoney Creek, Ancaster, Dundas, Glanbrook, and the lower city all have their own profiles. The only way to know your specific home's level is to test it.

How common is high radon in Hamilton? City-specific Hamilton survey data is more limited than for some Canadian cities, but Ontario provincial data shows about 8% of homes above the 200 Bq/m³ guideline (with some regions higher). Hamilton's decision to implement a municipal radon program reflects a recognition that local radon is a meaningful issue.

Can I claim Tarion warranty coverage if my new Hamilton home tests above 200 Bq/m³? Possibly. If your home is in its 7-year Tarion warranty window from the original possession date, and you have a qualifying long-term test result above 200 Bq/m³, you may be able to claim up to $50,000 of Tarion-covered mitigation (for APS signed on or after February 1, 2021). See our full Tarion radon warranty claim guide. Note: the municipal program and Tarion warranty are separate frameworks that can both apply.

How much does radon mitigation cost in Hamilton? Typical Ontario residential mitigation costs are $2,500–$4,500 for a sub-slab depressurization system installed by a C-NRPP-certified contractor. For Hamilton new-build owners within their Tarion warranty window with a qualifying test, mitigation cost may be substantially or fully covered by Tarion. Otherwise, the Canadian Lung Association's Lungs Matter program may offset up to $1,500.

Where can I buy a long-term radon test kit in Hamilton? You can order a RadonTest.ca $89 all-in long-term kit online and receive it within a few business days anywhere in Hamilton — kit + tracked outbound + prepaid tracked Canada Post return label + analysis at a C-NRPP-listed Canadian lab.

Do I have to disclose elevated radon when I sell my Hamilton home? Ontario uses OREA's Form 220 (SPIS), which is voluntary but, once completed, requires truthful answers. Independent of the SPIS, the latent-defect doctrine applies under common-law principles, and a known elevated radon reading is generally treated as a material defect requiring disclosure. See our full Real Estate Radon Guide.

When is the best time of year to test in Hamilton? The heating season — October through April — produces the highest indoor radon levels and is the recommended testing window per Health Canada (and is the mandated window under Hamilton's municipal program for testing required under the program).

Where can I find a C-NRPP-certified radon mitigator in Hamilton? The C-NRPP Find a Certified Professional directory lists certified measurement and mitigation professionals by area. Hamilton has a well-established C-NRPP-certified mitigator network given the municipal program's requirements.

Test your Hamilton home — $89, all in

Hamilton has one of the more layered radon regulatory frameworks in Canada — a municipal construction program, the Ontario Building Code radon rough-in requirement, and Tarion warranty coverage for qualifying new builds. For existing Hamilton homeowners outside the municipal program, the action item is the same one any Canadian homeowner should take: a long-term radon test that produces a real lab result.

RadonTest.ca — $89 all-in (plus applicable tax). Long-term 91-day alpha-track test kit. C-NRPP-listed device. Analysed at Lex Scientific in Guelph, Ontario — Canadian lab, C-NRPP listed, ISO/IEC 17025 accredited by CALA. Tracked Canadian shipping both ways. Written lab report PDF delivered to your inbox.

Order — $89 →

Important disclaimers

Not medical, legal, or building-code advice. This article provides general health and home-testing information for Hamilton homeowners and builders drawn from publicly available City of Hamilton, Health Canada, Cancer Care Ontario, Tarion, and Canadian Cancer Society materials. It is not medical advice, legal advice, building-code advice, or warranty advice. For specific construction compliance questions, consult Hamilton's Building Division directly. For legal matters, consult a qualified Ontario real estate lawyer.

Hamilton municipal program. Statements about Hamilton's municipal radon construction program reflect the City of Hamilton's publicly available Residential Construction Requirements for Radon Gas Mitigation. Specific requirements, testing protocols, options, and compliance procedures are subject to City of Hamilton bylaw and may be updated. Verify current requirements directly with the City of Hamilton's Building Division before relying on this article for a specific build. RadonTest.ca does not administer the municipal program.

Statistics and citations. Ontario provincial figures are from Health Canada's 2012 Cross-Canada Survey of Radon Concentrations in Homes. National figures are from Health Canada's Radon: What You Need to Know fact sheet (2025). Sources update published figures periodically.

Mitigation cost. The $2,500–$4,500 mitigation cost range is a typical Ontario residential figure. Actual costs vary by home, foundation, complexity, and contractor.

Tarion qualification. Statements that the alpha-track test "qualifies" or "meets Tarion test-type criteria" mean only that the test method matches Tarion's published test requirements. They are not a representation that any specific home, test, or claim will be approved. A complete Tarion radon warranty claim requires several conditions — see our Tarion claim guide and tarion.com for the complete requirements. RadonTest.ca is independent from Tarion and from the City of Hamilton.

Lungs Matter grant. Eligibility, grant amounts, and program availability for the Canadian Lung Association's Lungs Matter program may change. Verify directly at lung.ca before relying on the program.

Real estate disclosure. Statements about Ontario real estate disclosure reflect general OREA / common-law latent-defect principles. Specific obligations for any individual transaction depend on the facts; consult an Ontario real estate lawyer.

No diagnosis or treatment claims. RadonTest.ca sells radon test kits. We do not diagnose, treat, or prevent disease.

No warranty as to completeness. RadonTest.ca makes no warranty as to the completeness or accuracy of the information herein and accepts no liability for decisions made in reliance on this article.

Sources & further reading

Hamilton-specific

Ontario-specific

Health Canada / national

National associations and grants

Related RadonTest.ca articles