London & Middlesex
Radon testing and mitigation in London, Ontario
London is our home base and the city we test in most. Here’s what’s known about radon in London, and how to find out about your home.
- Region
- London & Middlesex
- Population
- about 422,000
- Public health
- Middlesex-London Health Unit
- Local factors
- 5 reasons to test
Is radon a problem in London?
Radon can exceed Health Canada’s 200 Bq/m³ guideline in any London home. No published local data rules any neighbourhood in or out. Across Ontario, about 1 in 8 homes tested at or above the guideline in the 2024 national survey. Locally, Shield-derived glacial soils, sandy or gravelly soils and new airtight construction are reasons to test. A 91-day test is the only way to know your home’s level.
Radon in London
London is our home base and the city we test in most. It also shows why radon is so hard to predict: the same street can have a 1910 brick house on a rubble foundation, a 1960s backsplit with a finished basement, and an infill home with a basement apartment. Each one pulls soil gas in differently.
The ground under London
The city sits on glacial till and moraine ridges, cut by the forks of the Thames. Along the river and its old channels, through Byron, Springbank and out toward Komoka, the ground turns to sand and gravel, which moves soil gas easily. The till itself carries rock fragments from the Canadian Shield, a source of uranium. West of the city, the Kettle Point black shale (one of Ontario’s most uranium-rich rock units) runs beneath western Middlesex.
London’s homes
Expect three patterns. In Old East Village, Old North, SoHo and Wortley Village, century homes often have floor drains, open sumps and stone or early concrete foundations. In Hyde Park, Fox Hollow, Lambeth and Talbot Village, newer homes are larger, taller and tighter, and Canadian research shows newer homes have tended to test higher. And across the city, basement suites added as secondary units put people where radon is usually highest.
What the data says
Ontario homes at or above Health Canada’s 200 Bq/m³ guideline in the 2024 Cross-Canada Survey, more than double the share found a decade earlier.Source: Cross-Canada Survey of Radon Exposure in the Residential Buildings of Urban and Rural Communities (2024)
Roughly how many homes per health region the first national survey (2009–2011) could test. Too few to clear any neighbourhood, which is why public maps can’t tell you about your house.Source: Health Canada — Cross-Canada Survey of Radon Concentrations in Homes, Final Report (2012)
Higher average radon exposure for rural residents than urban residents in a 2024 national study of 42,051 homes, mostly linked to drilled wells.Source: Goodarzi et al., Scientific Reports (2024) — rural communities and drilled-well annuli
Local results
Building a real radon picture for London
Public radon data for Southern Ontario towns is thin. The national surveys tested only a handful of homes per area. So we’re building our own: anonymized long-term results from homes we test, published by area once there are at least 30, so no single home can be identified and small samples can’t mislead.
London: collecting results. Already tested? Check your number and share it anonymously when you book.
Local factors
What can push radon up in London
Not a prediction for any single home, just the reasons a test is worth it here.
Glacial soils with Shield debris
The till and gravel left by glaciers here includes ground-up rock carried south from the Canadian Shield. Uranium travels with it, so radon can form close to your footings even where the bedrock itself is low in uranium.
Sandy or gravelly soils
Sand and gravel let soil gas move freely and over longer distances. More of the radon formed in the ground can reach the air around your foundation instead of decaying in place.
New, airtight construction
Canadian research shows newer homes have tended to test higher than older ones. Bigger, taller and tighter homes create a stronger stack effect that draws soil gas in through the slab.
Century homes
Fieldstone, rubble and early concrete foundations, earth-floor cellars and open sumps give radon many ways in. Older doesn’t mean safer: these homes still need a test.
Lived-in basements
Radon is usually highest on the lowest floor. Basement bedrooms, home offices and rental suites mean people spend hours a day where exposure is greatest.
Where we work
London neighbourhoods and nearby communities
- Old North
- Old South & Wortley Village
- Old East Village
- SoHo
- Byron
- Westmount
- Masonville
- Hyde Park
- Fox Hollow
- Sherwood Forest
- Oakridge
- Lambeth
- Talbot Village
- White Oaks
- Pond Mills
- Argyle
- Huron Heights
- Stoney Creek (London)
- Riverbend
- Warbler Woods
Nearby: Radon in Komoka · Radon in Dorchester · Radon in St. Thomas · Radon in Strathroy · Radon in St. Marys
How it works
From test to fix
- Book
Tell us about your London home. We reply within one business day.
- Test for 91+ days
A certified technician places long-term detectors on your lowest lived-in floor. You get an early reading at 2 weeks.
- Get your result
Lab-verified average, explained against Health Canada’s guideline.
- Fix it if it’s high
A sub-slab system designed for your foundation, at a fixed price, with results guaranteed.
Questions
Radon in London: FAQ
Is radon a problem in London?
Radon can exceed Health Canada’s 200 Bq/m³ guideline in any London home. No published local data rules any neighbourhood in or out. Across Ontario, about 1 in 8 homes tested at or above the guideline in the 2024 national survey. Locally, Shield-derived glacial soils, sandy or gravelly soils and new airtight construction are reasons to test. A 91-day test is the only way to know your home’s level.
How much does a radon test cost in London, Ontario?
A do-it-yourself long-term kit costs well under $100. A professional 91-day test, with placement by a C-NRPP certified technician, lab analysis and a written report, costs more but removes the guesswork about placement and interpretation. We quote a fixed price when you book.
I rent out my basement in London. Who should test?
The owner usually arranges it, but anyone can test. Place the detector in the suite’s main living or sleeping area, since Health Canada’s guideline applies wherever someone spends more than four hours a day. If the result is high, mitigation protects both units.
My north London home is only five years old. Do I still need to test?
Yes. Newer homes aren’t immune; research from the University of Calgary found newer Canadian homes have tended to test higher than older ones. Homes built before the 2024 Ontario Building Code usually don’t have a radon rough-in either.
Do you offer radon testing and mitigation in London?
Yes. We test and mitigate homes throughout London, including Old North, Old South & Wortley Village, Old East Village, SoHo, Byron and nearby. Call (226) 271-4667 or book online.
Radon is fixable. First, know your number.
Serving London, Komoka, Dorchester, St. Thomas, Strathroy and St. Marys.