Radon enters a home through cracks in the foundation, basement floors, crawlspaces, sump pumps, and openings around pipes or drains. It comes from uranium in the soil and seeps into the home due to pressure differences between the ground and indoor air
The Science Behind Radon Intrusion
Radon is a naturally occurring radioactive gas created when uranium in soil, rock, or water breaks down. This gas rises toward the surface and seeps into homes through any opening between the home and the ground.
Because indoor air pressure is usually lower than the pressure in the soil around the foundation, homes essentially suck radon in like a vacuum—especially in winter or when HVAC systems are running.
Most Common Ways Radon Enters a Home
Here are the top entry points:
- Cracks in basement floors or concrete slabs
- Gaps around utility penetrations (pipes, wiring, drains)
- Crawlspaces with exposed soil
- Sump pump pits or floor drains
- Openings in block walls or construction joints
- Well water (in rare cases, especially rural homes)
Even newer homes with tight seals are not immune. In fact, better insulation can trap radon more effectively, increasing indoor concentration.
Can Radon Enter Through Water?
Yes, but this is rare and usually only a concern for private wells. Radon gas can dissolve into groundwater and be released into the air when you use water for:
- Showering
- Washing clothes
- Cooking or boiling
This is more common in granite-rich soil regions. If you’re on well water, ask for a radon-in-water test.
How to Prevent Radon from Entering
You can reduce the chances of radon entry by:
- Sealing foundation cracks and gaps
- Covering crawlspace floors with a vapor barrier
- Installing a radon mitigation system (e.g. sub-slab depressurization)
- Keeping your basement well-ventilated
- Testing your home every 2 years
Remember: sealing alone won’t fix high radon levels—it just helps support an active mitigation system.
When to Take Action
If radon levels test above 4.0 pCi/L, the EPA recommends installing a mitigation system immediately. If your levels fall between 2.0–3.9 pCi/L, consider mitigation—especially if you have children, a finished basement, or plan to live in the home long-term.