Is radon a concern in the Tri-Cities area and should I install a mitigation system when finishing my basement?

Radon is a genuine concern in the Tri-Cities area, and finishing your basement is the ideal time to install a mitigation system — it's far less disruptive and expensive to do it now than after walls and flooring are in place.

Radon is a naturally occurring radioactive gas produced by the decay of uranium in soil and rock. It's colourless, odourless, and tasteless, and it seeps into homes through foundation cracks, floor drains, sump pits, and any gap where the structure meets the soil. Basements accumulate the highest concentrations because they're closest to the source and typically have less air exchange than upper floors. Long-term radon exposure is the second leading cause of lung cancer in Canada after smoking — Health Canada estimates radon causes approximately 3,200 lung cancer deaths per year nationally.

Radon Levels in the Tri-Cities

Coquitlam, Port Coquitlam, and Port Moody sit in a geographic area with elevated radon potential compared to coastal Metro Vancouver. The Tri-Cities are underlain by glacial till and granitic bedrock — particularly in the hillside areas of Burke Mountain, Westwood Plateau, and the slopes above Port Moody — which tend to have higher uranium content than the Fraser River delta soils found in Richmond or Delta. Health Canada's radon mapping data and BC Lung Association testing programs have identified pockets of elevated radon readings throughout the Tri-Cities, particularly in homes on higher ground with more direct soil contact.

That said, radon levels vary dramatically even between neighbouring homes. Soil permeability, foundation type, house pressurization, and ventilation patterns all influence how much radon enters and accumulates. The only way to know your actual level is to test — and you should test before and after finishing your basement.

Testing First

Health Canada's action level is 200 Becquerels per cubic metre (Bq/m³). A long-term alpha track detector placed in your basement for 90 days (ideally over the fall and winter months when windows are closed) gives the most accurate reading. These test kits cost $30-$60 and are available through the BC Lung Association's Take Action on Radon program, often at reduced cost. If your reading comes back above 200 Bq/m³, mitigation is strongly recommended. Readings between 100-200 Bq/m³ are worth mitigating, especially since finishing your basement will increase the time your family spends in that space.

Mitigation During Basement Finishing

The standard mitigation approach is sub-slab depressurization (SSD) — a pipe is core-drilled through the concrete slab into the granular layer beneath, and a continuously running fan draws radon-laden air from under the slab and exhausts it above the roofline before it can enter the living space. This system typically reduces radon levels by 80-99%.

Installing SSD during basement finishing is the smart move for several reasons. The contractor can route the pipe through a utility room or closet before walls are framed, keeping it concealed. The slab penetration is made before flooring goes down. And the cost is significantly lower when it's part of a larger project — a radon mitigation system installed during basement finishing typically runs $1,500-$3,500 in Metro Vancouver, compared to $2,500-$5,000 or more when retrofitted into a finished space where walls need to be opened and flooring disturbed.

Practical Steps for Your Project

Test your basement now with a long-term radon detector before construction begins — this gives you a baseline. Discuss rough-in for a mitigation pipe with your basement contractor at the framing stage, even if you want to wait for post-construction test results before installing the fan. Ensure your contractor seals all slab penetrations, floor drains, and the sump pit cover as part of the finishing work, since these are radon entry points regardless of whether you install a full SSD system. After finishing, retest for another 90-day period to confirm levels.

Radon mitigation is one of the highest-value health investments you can make during a basement renovation — the cost is modest relative to a full finishing project, and the protection is significant for a space your family will use daily.

Need help finding a basement contractor in the Tri-Cities familiar with radon mitigation rough-in? Vancouver Basement Finishing can match you with local professionals through the Vancouver Construction Network — browse the directory at vancouverconstructionnetwork.com/directory?trade=basement-renovations.