How do i deal with radon in my Fredericton basement if levels came back at 400 Bq/m3 after testing?

At 400 Bq/m³, you're at twice Health Canada's action guideline of 200 Bq/m³ — this needs to be addressed, and the good news is it's very fixable. Fredericton sits on geology that makes elevated radon common, and you're smart to have tested before assuming everything was fine.

Start with a second test to confirm. A 90-day long-term test (using an alpha track detector, $30–$50 from hardware stores or online) is the gold standard. Short-term tests can vary with seasonal pressure changes and ventilation habits. That said, at 400 Bq/m³ you're high enough that most certified mitigators will recommend proceeding with remediation rather than waiting — the confirmation test can run concurrently with getting quotes.

The primary fix for most Fredericton homes is sub-slab depressurization (SSD) — a licensed contractor cores through your basement slab, installs a suction point in the granular fill or soil beneath, and runs PVC pipe up through the house (or along an exterior wall) to a continuously running fan that draws radon out before it can enter. This is the most effective method and typically drops levels by 80–99%. In Fredericton's mix of post-war bungalows, split-levels, and older homes, SSD works well in most cases, though homes with block foundations or crawl spaces may need a slightly different approach.

Cost in the Fredericton market runs roughly:

• Basic single-suction-point SSD system: $2,500–$3,500


• More complex systems (multiple suction points, block foundation, crawl space): $3,500–$5,500


• Post-mitigation testing (strongly recommended 30–90 days after): $30–$50 DIY or included by some contractors

These figures are in line with New Brunswick's generally lower construction costs compared to central Canada.

Sealing visible cracks and openings in your slab and foundation walls is a worthwhile complementary step — not a standalone fix, but it reduces radon entry points and improves SSD system efficiency. Caulk floor-wall joints, seal around pipe penetrations, and fill visible cracks with polyurethane or epoxy. Budget $100–$300 in materials if you do it yourself.

Look for a C-NRPP certified radon mitigation professional (Canadian National Radon Proficiency Program) — this is the recognized credential in Canada. You can search the C-NRPP directory at c-nrpp.ca to find certified professionals serving the Fredericton area. Ask any contractor you contact whether they hold this certification before booking.

One important note: if you're planning to finish your basement, deal with radon first. Finishing over an unmitigated radon problem traps the gas in your living space and makes future remediation more complicated and expensive. Get the system in, confirm post-mitigation levels are below 200 Bq/m³ (ideally below 100), then proceed with your renovation.

NB Power's Total Home Energy Savings Program doesn't directly rebate radon mitigation, but improving your home's air sealing as part of a broader energy retrofit can sometimes interact with radon levels — worth mentioning to your mitigator so they can assess your ventilation setup as part of the job.

Browse certified contractors in our directory at New Brunswick Construction Network — and don't sit on this one too long. At 400 Bq/m³ with regular basement use, remediation is worth prioritizing this season.