How do I deal with radon when finishing a basement in New Brunswick?

Radon testing and mitigation must be completed before any basement finishing in New Brunswick. NB has some of Canada's highest radon levels, with many homes exceeding Health Canada's action guideline of 200 Bq/m³. Finishing a basement without addressing radon first creates a health hazard and wastes your renovation investment.

Testing comes first — hire a certified radon measurement professional or purchase a long-term radon test kit from the Canadian Cancer Society. Short-term tests (2-7 days) provide quick results but long-term tests (3+ months) give more accurate readings since radon levels fluctuate with weather, soil conditions, and seasonal changes. Test during the heating season when your home is closed up, as this represents worst-case conditions. If levels exceed 200 Bq/m³, mitigation is required before finishing.

Radon mitigation in NB typically involves sub-slab depressurization — a system that draws radon-laden air from beneath your basement floor and vents it safely outside above the roofline. A certified radon mitigation contractor installs a PVC pipe through your basement floor into the gravel bed beneath, connects it to a specialized fan, and routes it outside. This creates negative pressure under the slab, preventing radon from entering your home. Mitigation costs $2,500-$4,500 in NB and must be completed before any basement finishing begins.

NB's geology makes radon particularly problematic. Much of the province sits on granite bedrock and uranium-bearing shale formations that naturally produce radon gas. The Fredericton area, Saint John River valley, and parts of Charlotte County show elevated radon potential. Spring snowmelt and NB's freeze-thaw cycles create soil movement that can open new pathways for radon entry. Even homes that previously tested low can develop radon problems as foundation settling creates new cracks.

Basement finishing must work with your mitigation system. If you're installing a radon mitigation system, plan your basement layout around the pipe routing. The system requires access to the sub-slab area and an exterior wall for the fan and vent pipe. Seal all foundation cracks, utility penetrations, and floor-wall joints with polyurethane caulking before finishing. Install a continuous poly vapour barrier on the warm side of your insulation — this also helps reduce radon infiltration through the walls.

Post-mitigation testing confirms system effectiveness. After your mitigation system is installed and operating, retest radon levels to ensure they've dropped below 200 Bq/m³. Most properly installed systems reduce radon by 90%+ and maintain effectiveness for decades with minimal maintenance. The mitigation fan runs continuously — budget about $150-$200 annually in electricity costs.

Timing is critical for NB basement projects. Complete radon testing during winter months when your home is sealed up. If mitigation is needed, install it in spring before starting your basement finishing. This allows the system to operate and stabilize before you invest in framing, insulation, drywall, and flooring. Starting a basement renovation without addressing radon first means potential tear-out later if high levels are discovered.

Don't skip this step to save money. Radon is the leading cause of lung cancer in non-smokers and the second leading cause overall. NB's Maritime climate means basements are used year-round as living space, increasing exposure time. A properly mitigated basement provides decades of safe use, while an unmitigated high-radon basement puts your family's health at risk regardless of how beautifully it's finished.

Need help finding radon testing and mitigation professionals in your area? New Brunswick Renovations can connect you with certified radon contractors through the New Brunswick Construction Network directory.