How Often Should You Test for Radon?
A single radon test is not a permanent answer. Radon levels change over time as foundations settle, soil conditions shift, and homes are renovated. The question is not whether to retest. It is when.
This guide gives you a clear retesting schedule based on your situation.
The retesting schedule
The EPA recommends retesting every two years under normal circumstances. Beyond that baseline, specific events should trigger an immediate retest:
Baseline retesting interval recommended by the EPA. Radon levels can shift as soil settles and conditions change.
Any work that affects your foundation, basement, or below-grade structure: finishing a basement, adding a sump pump, waterproofing, new concrete, or structural modifications.
Even if the seller provided a recent test. Conditions may have changed, and you want a baseline under your own living patterns.
Test within 24 hours to 30 days after the system is installed. Then retest annually to confirm the system is still working effectively.
Major flooding, earthquake, or sustained heavy rain can alter soil gas pathways and shift radon levels. Test once conditions normalize.
If you start using a previously unused basement as a bedroom, office, or play area, test that space before people spend regular time there.
Why radon levels change over time
Radon is not a static number. Several factors cause levels to drift:
- •Foundation settling. As your home ages, the foundation develops new cracks and gaps. Hairline fractures in concrete are invisible but sufficient for radon entry.
- •Soil moisture and pressure. Wet seasons increase soil gas pressure beneath your foundation. Frozen ground in winter can cap soil gases and force more radon through foundation openings.
- •Seasonal variation. Homes are typically more sealed in winter (windows closed, less ventilation), which means radon accumulates more. Summer readings tend to be lower. A long-term test captures the seasonal average.
- •HVAC changes. A new furnace, modified ductwork, or a sealed crawl space changes airflow patterns and pressure differentials in your home.
- •Renovations. Finishing a basement adds living space in the highest-concentration zone. New construction can seal entry points or create new ones depending on the work.
What about mitigation systems?
Tipper's practical approach
Here is what Tipper actually does, and recommends:
- •Test every two years using a short-term kit. It costs $15 and takes 48 hours. There is no reason not to.
- •If you have a mitigation system, test annually. Mark it on your calendar.
- •If you renovate anything below grade, test before and after.
- •If you buy a home, test in the first month, regardless of what the seller's test showed.
- •Keep your results. A history of readings over time is more informative than any single number.
Set a recurring reminder. Phone calendar, task app, whatever you actually use. "Retest radon" every January. Two years goes faster than you think, and the actual work takes less than five minutes.
Time to retest? Grab a kit from Tipper's picks , all EPA-approved, all include the lab fee.