How Does Radon Enter a Home?

How does radon enter a home? Radon moves from the ground into a building through openings where the foundation contacts the soil. Some pathways are obvious, while others are tiny, such as hairline cracks or floor-to-wall joints. This does not mean a home is damaged or poorly built.

Normal construction openings can allow soil gas to enter both new and older houses. For the basics, check out our Radon Basics articles .

Where Does Radon Come From?

Radon is a naturally occurring radioactive gas formed as uranium breaks down in soil and rock. It can travel through pores and gaps in the soil as part of the air beneath a building.

The amount reaching a home depends on its soil, foundation, entry routes, weather, and indoor pressure. A neighbour’s result cannot reliably predict your level. Take Action on Radon’s Manitoba resources provide more information about radon testing and awareness in the province.

Why Is Radon Drawn Into a Home?

The air pressure inside a home is often slightly lower than the pressure in the soil surrounding its foundation. Health Canada explains that this difference can draw soil air, including radon, into the building.

Warm air, heating equipment, fireplaces, exhaust fans, and ventilation can affect indoor pressure. The result is similar to a weak vacuum that encourages soil gas to move through small openings.

Common Radon Entry Points

Radon can enter wherever a building has an opening or pathway to the ground.

Floor-to-Wall Joints

The joint where the basement floor meets the foundation wall can form a narrow pathway around much of the slab’s perimeter, even when it appears tightly closed.

Foundation Cracks

Concrete may develop small cracks through shrinkage, settlement, or normal movement. A crack does not need to look severe to permit soil gas movement, but its appearance cannot reveal how much radon is entering.

Sump Pits

A sump pit often connects to the drainage stone beneath the slab. An open sump or loose-fitting lid can provide soil gas with a direct route into the basement.

Plumbing and Utility Penetrations

Gaps around water lines, sewer pipes, electrical conduits, support posts, and other services can create pathways through the slab or foundation.

Drains and Other Openings

Floor drains, cleanouts, unused pipe openings, crawl spaces, and exposed soil may also allow radon-containing soil gas into a home.

These entry points can exist in well-built and newly constructed homes. Health Canada also identifies construction joints, service openings, drains, sumps, wall cavities, and foundation cracks as potential entry routes.

Can Radon Move Through Solid Concrete?

Concrete is not perfectly airtight, so a limited amount of radon can move through it. However, cracks, joints, penetrations, drains, sump pits, and exposed soil are generally more important routes for soil gas.

A dry, well-maintained basement can still have elevated radon. No visible damage does not mean the foundation is airtight.

Does Sealing Foundation Cracks Stop Radon?

Sealing visible openings can reduce soil gas entry and is often part of a professional mitigation installation. However, sealing alone does not reliably solve every elevated-radon problem.

Some pathways are hidden, and soil gas may move toward another opening while the pressure difference remains.

Health Canada’s Radon Reduction Guide for Canadians identifies active soil depressurization as the most effective and reliable reduction method. A fan and pipe draw soil gas from beneath the foundation and release it outdoors before it enters the home.

Can You Identify Radon by Looking at the Foundation?

No. A visual inspection can identify possible entry points, but it cannot determine the radon concentration.

A home with no obvious cracks may have elevated radon, while another with visible cracks may produce a lower result. A sealed sump or radon-ready feature also does not confirm a low level. The only reliable answer comes from measurement.

Testing Is the Only Way to Know

Radon cannot be seen, smelled, or tasted. Health Canada’s guide for radon measurements in homes recommends testing for at least three months to estimate a home’s average concentration.

Place the detector on the lowest level where someone spends at least four hours per day. For many households, this may be a finished basement, office, recreation room, or main floor. Homeowners hiring someone to test or mitigate can verify their certification through the Canadian National Radon Proficiency Program.

Review Short-Term vs. Long-Term Radon Testing: Which One Do You Need? before choosing a test.

Frequently Asked Questions

Can radon enter through a sump pit?

Yes. A sump may connect directly to the drainage material beneath the slab, making an open or poorly sealed pit a potential entry route.

Can radon enter through basement cracks?

Yes. Cracks can permit soil gas movement, but their size or appearance cannot predict the home’s radon level.

Can radon enter a home without a basement?

Yes. Radon can enter slab-on-grade homes, crawl-space homes, and other buildings with foundations that contact the ground.

Will sealing every visible crack eliminate radon?

Not necessarily. Sealing may help, but it does not control hidden pathways or the pressure beneath the foundation.

Understand the Pathway, Then Test

Radon can move from the soil into lower-pressure areas inside a home through many small foundation openings. These pathways may exist in both new and older Manitoba homes, and their appearance cannot reveal the indoor concentration.

Testing is the only reliable way to know. If elevated radon is confirmed, proven mitigation methods are available. RadonPatrol provides professional Manitoba Radon Testing with clear results and practical next steps. Book a long-term test to understand what is happening in your home.