Radon in Strata and Multi-Unit Buildings: What BC Owners and Councils Need to Know
Who tests, who pays, and who is responsible for radon in BC strata buildings — a practical guide for unit owners, strata councils, and property managers.
Radon in a single-family home is straightforward: the homeowner tests, the homeowner decides, and a certified contractor mitigates if levels are above Health Canada’s guideline of 200 Bq/m³. In a strata building, nothing is that simple.
Who is responsible for testing? What happens when elevated radon is found in a unit versus common areas? Can an owner install a mitigation system without council approval? And what is a strata corporation’s exposure if the building has never been tested?
These questions are coming up more often as radon awareness grows in BC. BC Radon Control is C-NRPP certified for both testing and mitigation, including multi-unit residential and commercial buildings throughout the Fraser Valley.
Why Multi-Unit Buildings Are a Radon Concern
Radon enters buildings from the soil beneath them. In multi-unit buildings, basement suites, ground-floor units, and below-grade parkades and storage areas carry the highest risk. But strata buildings have a second risk factor that single-family homes do not: the stack effect.
Warm air inside a building rises and exits through upper floors, mechanical rooms, and vents. As it leaves, it creates negative pressure at lower levels, drawing outdoor air — and radon from the soil — upward through the building. Radon can travel through elevator shafts, stairwells, utility chases, and unsealed penetrations between floors.
This is why units on upper floors are not automatically safe. Any unit with air exchange from below-grade spaces is potentially at risk. Testing at the lowest occupied level tells you about that floor — it does not tell you about the rest of the building.
Who Is Responsible for Radon Testing?
In a BC strata building, responsibility depends on what is being tested.
Unit owners are responsible for the air within their own unit boundaries. A unit owner can commission a radon test from a C-NRPP certified technologist without needing strata council approval for the test itself.
Strata corporations are responsible for common property. Underground parking, mechanical rooms, amenity spaces, lobbies, and below-grade storage are typically common property under BC strata law. Testing these areas falls to the strata council, not individual unit owners.
A comprehensive radon assessment of a strata building requires both: unit owners testing their suites, and the strata council commissioning tests for common areas. A corporation that has never tested common property — particularly underground parking and below-grade mechanical rooms — has no way of knowing whether a problem exists.
What a Strata Testing Protocol Looks Like
For a multi-storey building, Health Canada guidelines recommend testing at multiple points:
- The lowest occupied residential level (most critical)
- Other occupied floors on a sampling basis, including upper levels where stack-effect migration is a concern
- Common areas at or below grade: parkades, storage rooms, amenity spaces, fitness centres
Individual unit testing uses a long-term alpha track detector (91+ days minimum) or a professional short-term test (96 hours). For strata common areas, professional monitoring equipment that records hourly readings is standard — this produces documentation suitable for council minutes and building management records.
BC Radon Control provides commercial and strata radon testing throughout the Fraser Valley, including building-wide protocols for multi-unit residential and mixed-use buildings. Our C-NRPP certified technologists document results in a format strata councils can retain and share with owners.
When Results Are Elevated: Who Pays for Mitigation?
This is where BC strata law and radon collide in ways that are not always obvious.
Elevated radon in a unit: Effective mitigation for a ground-floor strata unit almost always involves some modification to common property — drilling through a slab, routing pipe through a common area, or mounting a fan on an exterior wall. Under BC strata law, modifications to common property require strata council approval. A unit owner cannot unilaterally install a mitigation system without that approval, even if the radon level in their suite is well above the action level.
The practical path: the unit owner documents the test result, notifies the strata council in writing, and requests a council decision on a remediation plan. This starts the strata bylaw process and creates a paper trail. In most cases, a well-framed request — supported by a C-NRPP certified test report and a contractor quote — moves through a strata council efficiently.
Elevated radon in common areas: If strata-commissioned testing finds elevated levels in the underground parking or another common area, mitigation is the strata corporation’s responsibility. This may involve HVAC adjustments, mechanical ventilation upgrades to the parkade, or sealing radon entry points in common property. For buildings where the stack effect is driving radon to upper units, adjusting the building’s HVAC pressure balance is often part of the solution.
Commercial properties: For workplaces, schools, and daycares, Health Canada also recommends testing. Elevated radon in a workplace above 200 Bq/m³ is a recognized occupational health concern. BC Radon Control tests and mitigates commercial properties alongside residential and strata work — contact us to discuss a commercial assessment.
Radon and Strata Real Estate Transactions
If you are buying a below-grade strata unit in BC, requesting a radon test as a condition of purchase is strongly recommended. The BC Financial Services Authority has identified elevated radon as a material latent defect — a defect that sellers must disclose if they are aware of it. A seller who has tested and found elevated levels without mitigating is required to disclose that result.
For buyers, this means: insist on a short-term radon test conducted by a C-NRPP certified technologist. A DIY kit placed and retrieved by the seller does not satisfy a buyer’s subject condition. For more on how radon works in BC real estate transactions — what test is accepted, how to interpret results, and how to negotiate around elevated levels — see our guide on radon and real estate in BC.
Getting a Strata Radon Assessment in the Fraser Valley
BC Radon Control provides radon testing and mitigation for strata buildings, townhouse complexes, schools, daycares, and commercial properties throughout the Fraser Valley. We are C-NRPP certified, WCB covered, and fully insured. We work directly with strata councils, property managers, and individual unit owners to provide the documentation and testing protocols that multi-unit buildings require.
If you’re in the Fraser Valley and need certified strata radon testing or a mitigation quote for a multi-unit building, contact BC Radon Control to discuss your building’s needs. For information on our residential testing services, visit our radon testing page. For the mitigation process and what installation involves, see our radon mitigation page.
Have questions about radon in your home?
Speak with a C-NRPP certified professional in the Fraser Valley.