There's a widespread misconception that radon is only a problem in houses with basements. In reality, radon can accumulate in any building — including condominiums, apartments, and multi-unit residential buildings. If you live above the ground floor, your risk is lower, but it is not zero.
How Radon Gets Into Multi-Unit Buildings
Radon enters buildings the same way regardless of building type: it migrates from uranium-bearing soil and rock through foundation materials — cracks in concrete slabs, pipe penetrations, and floor drains. In a high-rise condominium, the building's foundation is the primary entry point.
From the foundation, radon can travel vertically through elevator shafts, utility chases, stairwells, and pipe conduits. It can also move laterally through the building structure. The result is that radon concentrations in multi-unit buildings are not simply a function of floor height — they depend heavily on the building's construction, ventilation design, and how airtight individual suites are.
Does Floor Level Matter?
Generally, yes — but not as predictably as people assume.
- Ground-floor and basement suites are at highest risk. They are closest to the soil source and may have concrete slab floors in direct contact with the ground.
- Second and third floor suites typically see lower levels than ground floor, but elevated readings are still documented in mid-rise buildings.
- Higher floors generally have lower radon — but stack effect, air handling, and building tightness can create unexpected pockets of accumulation even on upper floors.
The only way to know your unit's radon level is to test. Health Canada recommends testing in the lowest livable space within any unit, including condominiums.
Who Is Responsible for Radon Testing in a Condo?
This varies by province and building type, and it's one of the most confusing aspects of condo radon management.
Individual unit owners are generally responsible for testing their own suite. Nothing prevents you from purchasing a test kit and placing it in your unit — this is the simplest first step.
Condo boards and property managers may have responsibility for testing and mitigating common areas and below-grade spaces (parking garages, storage rooms, amenity rooms) depending on your condominium declaration and provincial building code requirements.
The 2015 National Building Code of Canada introduced requirements for radon-resistant construction in new low-rise residential buildings, and some provinces have gone further with mandatory testing requirements for certain building types. Check with your provincial health authority for current requirements in your jurisdiction.
Radon in Basement Suites and Secondary Suites
Basement suites and secondary suites are among the highest-risk living situations for radon exposure in Canada. They are typically below-grade, often have less ventilation than main-floor living spaces, and their occupants — frequently renters — may be unaware of radon risk.
If you are a landlord renting a basement suite, testing for radon is both a responsible practice and, in some provinces, required by health and safety regulations. If you are a tenant in a basement suite, you have the right to ask your landlord to test, and you can also purchase and place a test kit yourself. See our guide on radon testing for rental properties.
What Can You Do About Radon in a Condo?
Mitigation options for condo owners are more limited than for detached homeowners — you can't drill through the slab yourself without board approval, and access to sub-slab space may not be possible. However, several options exist:
- Test first. Get your unit's baseline level. Use a long-term alpha track test kit or a continuous monitor like the Airthings Wave.
- Improve ventilation. Opening windows and running mechanical ventilation (HRV/ERV) at higher settings can reduce radon concentrations, especially on lower floors. This is a partial measure, not a permanent solution.
- Bring results to the condo board. If your result exceeds 200 Bq/m³, present it formally to your condo corporation. Boards are increasingly aware of liability exposure related to radon, particularly in buildings with ground-floor suites and parking below occupied units.
- Advocate for building-level mitigation. Commercial-scale SSD systems exist for multi-unit buildings. A certified mitigator can assess the building and propose a system. Costs are typically shared across owners.
- Seal entry points in your unit. Any visible cracks or penetrations in your suite's concrete floor or walls can be sealed with polyurethane caulk or hydraulic cement as a supplementary measure.
Continuous Monitors for Renters and Condo Owners
If you rent or live in a condo, a continuous radon monitor gives you real-time visibility into your radon levels. This is especially useful when you want ongoing data, when you're evaluating the effect of ventilation changes, or when you want portable testing capability across different units or locations.
Popular options for condo and apartment use:
- Airthings Wave — Bluetooth-connected, app-based, compact and unobtrusive
- Airthings Corentium Home — battery-powered, portable, no connectivity required
- RadonEye RD200 — fast response digital monitor with Bluetooth app integration
- Airthings View Radon — WiFi-connected with a built-in display, ideal for permanent installation
For official C-NRPP certified testing (required for real estate transactions and some insurance purposes), use an alpha track test kit. Digital monitors are excellent for ongoing monitoring but are not accepted as formal test documentation in all contexts.
