Radon Testing New Brunswick: Levels, Risks, and the Holdback Clause Buyers Should Know

Radon is an invisible, odorless radioactive gas that seeps through foundation cracks and accumulates in basements. It is the second leading cause of lung cancer after smoking, and New Brunswick has higher average radon concentrations than many other Canadian provinces due to the composition of its underlying bedrock geology.

If you are buying a home in New Brunswick, you need to understand the testing process, the remediation threshold, and a specific contract clause that lets you protect yourself without delaying the closing.

What Constitutes a Dangerous Radon Level

Health Canada sets the national guideline at 200 Becquerels per cubic meter (Bq/m3). If a home tests above 200 Bq/m3 on a long-term test, remediation is recommended. The World Health Organization uses a lower reference level of 100 Bq/m3, but the Canadian standard is the legally relevant figure for real estate transactions in New Brunswick.

Radon levels vary dramatically house to house -- two adjacent homes on the same street can produce wildly different readings depending on foundation condition, ventilation, and the specific geology beneath each property. You cannot assume a property is safe because the neighbor's test came back clean.

Why Standard Home Inspections Miss Radon

A general home inspector may offer a short-term radon screening (48 to 72 hours), but these snapshots are unreliable. Radon levels fluctuate with weather, wind patterns, heating system use, and season. A 48-hour test done in August with open windows might show 50 Bq/m3 on a property that averages 350 Bq/m3 during winter months when the house is sealed.

Health Canada recommends a long-term test of at least 91 days during the heating season (October through April) for an accurate reading. That 91-day minimum creates an obvious problem: your closing date is typically 30 to 45 days from the accepted offer. You cannot complete a proper radon test before you take possession.

The NBREA Radon Holdback Clause

The New Brunswick Real Estate Association addresses this timing problem directly. NBREA provides a standard radon holdback clause for purchase agreements. Here is how it works:

1. You and the seller negotiate a holdback amount at the time of the offer -- typically equivalent to the cost of a mitigation system, which runs $3,000 to $5,000.
2. On closing day, that amount is held in your lawyer's trust account rather than released to the seller.
3. After closing, you deploy a long-term radon test (minimum 91 days) in the lowest lived-in level of the home.
4. If the result exceeds 200 Bq/m3: The holdback funds are released to you to install a sub-slab depressurization system, which can reduce indoor radon levels by over 80%.
5. If the result is below 200 Bq/m3: The held funds are released to the seller.

This clause is the single most practical tool available to buyers in New Brunswick for managing radon risk without walking away from an otherwise sound deal.

Where Radon Risk Is Higher in New Brunswick

Radon risk is not uniform across the province. It correlates with bedrock type and soil characteristics. Areas with granite, shale, or certain sedimentary formations tend to produce higher radon concentrations. Parts of the Fredericton area, the central highlands, and certain sections of the Saint John River valley have documented elevated readings.

But predicting radon based solely on geography is unreliable. Even in areas considered low risk, individual homes can test high due to specific foundation conditions. The only way to know is to test.

Mitigation If Your Home Tests High

A sub-slab depressurization system is the standard remediation approach. A contractor installs a small pipe through the basement floor slab connected to a fan that draws radon-laden air from beneath the foundation and vents it safely above the roofline. The system runs continuously and uses minimal electricity.

Installation costs range from $3,000 to $5,000 for a typical residential property. Post-installation testing should confirm that levels have dropped well below 200 Bq/m3. Most systems reduce radon concentrations by 80% or more.

If you are buying a home with an unfinished basement that you plan to convert to living space, test before renovation. It is far cheaper and less disruptive to install a mitigation system before you finish the basement than after.

What to Do as a Buyer

1. Include the NBREA radon holdback clause in your offer. This is standard practice and sellers familiar with New Brunswick real estate will expect it.
2. Deploy a long-term test kit as soon as you take possession. Alpha-track detectors are inexpensive and available from certified radon measurement providers. Place the detector in the lowest level of the home that you use or plan to use as living space.
3. Do not rely on short-term screening alone. A short-term test during your inspection period gives you a rough indicator, but the holdback clause exists precisely because the definitive test takes 91+ days.
4. Budget for possible mitigation. Even if you do not end up needing a system, factoring $3,000 to $5,000 into your contingency fund prevents a financial shock.

For a full due diligence checklist that covers radon, well water, septic, oil tanks, and flood risk in New Brunswick, the New Brunswick First-Time Home Buyer Guide walks through every environmental inspection a buyer needs.

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