Radon in Hamilton: one in seven homes tested above the guideline

Hamilton's own numbers are worse than the provincial average

Hamilton Public Health surveyed 294 homes and found 42 of them, about 14 percent, exceeded Canada's radon guideline. That is roughly one in seven Hamilton homes, against a Health Canada Cross-Canada Survey figure of about 8 percent for Ontario as a whole. Radon is a colourless, odourless soil gas and the second leading cause of lung cancer after smoking, so this is a genuine health issue rather than a renovation upsell.

Health Canada's guideline is 200 becquerels per cubic metre (Bq/m³), averaged over the normal occupancy area. Crucially, a valid measurement requires a minimum three-month test during the heating season. Two-day charcoal kits tell you very little, and no reputable mitigation decision is made on one.

"Radon is the rare renovation topic where the honest answer is often 'test first, and you may not need me at all'. A three-month test costs less than a service call. If it comes back under the guideline, you have bought certainty. If it comes back high, you have bought a reason to act."

Mitch Fraser, owner, Ontario Contracting Co.

The Hamilton building-permit angle nobody mentions

Hamilton's residential construction requirements call for radon rough-in work on new construction and additions to low-rise residential buildings: a 100 mm pipe rough-in through the slab, adjacent an exterior wall, extending into a centrally located granular bed and continuing above the slab. This is also why Radon Inspection appears as its own stage in Hamilton's 24-stage inspection table, a detail we cover in Hamilton's fee schedule and inspection stages.

Provincially, the 2024 Building Code requires a rough-in for a future sub-slab depressurization system in new Part 9 residential construction, along with soil-gas air barrier measures: sealed joints and penetrations in assemblies contacting the ground. In other words, if you are building an addition in Hamilton, the radon provisions are not optional extras, they are part of the permit.

What mitigation actually is

The standard fix is active soil depressurization: a pipe and fan system that draws air, and therefore radon, from beneath the foundation and exhausts it above the roofline. It is typically a one-day installation by a certified radon professional (look for C-NRPP certification). If you are already finishing a basement, the rough-in is dramatically cheaper to install before the slab and framing are closed up than after, which is why we raise it during design on Hamilton basement projects rather than after.

If your home is new, Tarion may pay

For newly built Ontario homes, the Tarion warranty covers up to $50,000 of radon mitigation for the full seven years of the warranty where levels test at or above the Health Canada guideline, with a claim requiring a minimum three-month test. Renovations to existing homes fall outside Tarion entirely, a boundary explained in our guide to the Tarion gap.