Radon gas is a silent threat in many Canadian homes, especially those with older or compromised foundations. As a naturally occurring radioactive gas that forms from the breakdown of uranium in soil and rock, radon can infiltrate homes through various entry points.

While most homeowners know that radon can seep into their living spaces through floors and crawl spaces, many underestimate the role of foundation walls in allowing radon to enter.

At Peerless Air, we specialize in identifying and mitigating radon risks in residential and commercial structures.

Addressing radon entry through foundation walls is a crucial part of a comprehensive mitigation strategy, and we approach it with proven methods designed to create long-term protection and peace of mind.

Radon Gas in Foundation Walls. Closeup of a cracked gray cement fence wall.

Why Foundation Walls Are a Problem

Foundation walls—especially those made from poured concrete or concrete blocks—may develop tiny cracks or porous areas over time. Even the most minor fissure can become a pathway for radon to move from the surrounding soil into the structure.

This is particularly true in regions with high ground radon concentrations or homes with negative air pressure that pulls gases inward. Radon doesn't need large openings to infiltrate.

It travels upward from the soil and enters through imperfections, construction joints, utility penetrations, and gaps between the wall and slab. If we don't actively seal or manage these vulnerabilities, radon will accumulate over time, often without any visible warning signs.

Testing and Diagnosis

Before we apply any mitigation technique, we begin with professional radon testing. This allows us to measure the radon concentration levels inside the home and identify whether the foundation walls are likely contributors.

If tests reveal elevated levels and we observe signs of wall deterioration or poor sealing, we recommend a direct mitigation plan that includes addressing the walls.

Depending on the situation, we use both short-term and long-term testing methods. We often test multiple areas for homes with unfinished basements or visible structural issues to better understand how radon enters and where it concentrates.

Sealing Cracks and Penetrations

One of the first steps in reducing radon entry through foundation walls is sealing visible cracks, gaps, and utility penetrations. We use high-grade, radon-resistant sealants that remain flexible and durable over time.

These products are specifically designed to withstand pressure changes and minor shifts in the foundation, ensuring long-term effectiveness.

This process often includes sealing:

Cracks in poured concrete or masonry block walls
Gaps around pipes or electrical conduits
Cold joints where the foundation wall meets the slab
Spaces around windows or vents in the basement walls

While sealing alone will not always reduce radon to safe levels, it's an essential component of any mitigation system and significantly improves the performance of other methods.

Block Wall Depressurization

We recommend block wall depressurization for homes with hollow concrete block (CMU) foundation walls. This method draws radon gas from the hollow cores of the concrete blocks before it can enter the interior air.

We drill access points into the wall and install a vent pipe connected to a radon fan. The system actively pulls the gas out of the wall cavity and exhausts it safely above the roofline. This reduces the gas concentration inside the wall and prevents it from leaking into the interior space.

Depending on the home's structure, this approach is especially effective when combined with sub-slab depressurization or crawl space mitigation.

Interior Wall Coatings and Membranes

Another highly effective solution we provide is the application of radon-resistant wall coatings. These specialized paints and sealers are applied to the interior surface of the foundation wall and form a barrier that prevents gas intrusion.

We sometimes install wall membranes that create a continuous seal from wall to floor for added protection.

This method benefits unfinished basements or utility rooms where wall surfaces are exposed. It's also useful for homeowners who plan to finish their basements and want to control radon before installing drywall or flooring.

Ventilation and Air Pressure Management

Managing indoor air pressure is a crucial part of any radon mitigation strategy. When negative pressure builds inside the home, it draws soil gases—including radon—through the foundation and walls.

We evaluate each home's airflow and recommend ventilation improvements that help equalize pressure and reduce radon infiltration.

This may include installing energy recovery ventilators (ERVS), improving basement exhaust, or upgrading mechanical systems to reduce vacuum effects.

Monitoring and Maintenance

After implementing radon mitigation measures targeting the foundation walls, we will confirm the results with post-mitigation testing.

We aim to reduce radon levels below Health Canada's recommended action level of 200 Bq/m³—ideally much lower.

We also recommend homeowners continue monitoring radon levels periodically, especially after renovations or seasonal changes that may affect air pressure or sealing.

Your Partner in Radon Safety

At Peerless Air, we understand that no two homes are alike. Our approach is always customized to each homeowner's unique construction, radon levels, and needs.

Regarding foundation walls, we combine detailed inspection, specialized materials, and proven techniques to deliver effective and long-lasting radon mitigation.

If you've tested your home and found elevated radon levels—or if you suspect your foundation walls may be a source of radon entry—reach out to us today. We're here to help you create a safer, healthier environment with solutions backed by expertise and experience.

How to Address Radon Gas in Foundation Walls