Test your home
- Free test kit from TDEC, Tennessee’s radon program.12
- Buy a kit by phone: 1-800-SOS-RADON (1-800-767-7236).
- Live help with your questions: 1-800-55RADON (1-800-557-2366).
- Find a certified pro: NRPP 800-269-4174 · NRSB 866-329-3474.
Williamson County Radon · Research brief · October 2026
Radon in Williamson County
One county, three construction-code stories—and a verified county maximum of 17.2 pCi/L in the state dashboard snapshot.
Williamson is an EPA Zone 1 county. Testing remains the only way to know a specific home’s level; a county designation or passive construction feature is not a house-level result.4
Radon in Williamson County, Tennessee: quick answers
EPA zone: Zone 1Region: Middle TennesseeState test data: State test figures confirmed on repeat checks
Is radon a problem in Williamson County, Tennessee?
Yes, it can be. Williamson County is in EPA Zone 1, the highest radon-potential category, where the predicted average indoor screening level is above 4 pCi/L. Levels vary from house to house, so a test is the only way to know your home's level.
Do new homes in Williamson County, TN have to be built radon-resistant?
In Brentwood, Nolensville and Thompson's Station, yes: each adopted the radon appendix. Franklin's adopted code doesn't include it, and unincorporated Williamson County's appendix list couldn't be confirmed. Local code details
How do I test my home for radon in Williamson County?
Order a free short-term kit from the Tennessee Radon Program online or by calling 1-800-232-1139. Place it on the lowest lived-in floor, about 3 feet off the floor, for 3 to 5 days, then mail it back right away. How to test your home
What radon level means I should fix my home?
EPA recommends fixing your home if radon is 4 pCi/L or higher, and considering a fix between 2 and 4 pCi/L. Confirm a high short-term result with a second test first. What your result means
Who can test or fix radon in Williamson County?
Tennessee doesn't license radon professionals, so look for NRPP or NRSB certification. Search both national directories by ZIP code; certified professionals often serve Williamson County from nearby cities. How to choose a radon professional
01
Risk profile
The local testing picture
The verified county snapshot includes a maximum of 17.2 pCi/L.
The Tennessee Radon Testing dashboard shows a verified maximum of 17.2 pCi/L for Williamson County in its 2022–2023 view.1 The county average and median have not been verified and are withheld. A county summary cannot predict an individual home.
17.2verified maximum · pCi/L
—average · unverified
—median · unverified
A separate 2022 disparity report, using a different 10-year CDC-derived dataset, found Williamson had Tennessee’s highest testing rate: 39 tests per 1,000 housing units.5 That testing-rate study and the 2022–2023 state dashboard should be treated as separate datasets.
02
Code map
Jurisdiction changes the answer
A Franklin address and a Brentwood address can sit in the same county and face different radon provisions.
Select a jurisdiction to see the latest public record the research could verify. This is a code-adoption snapshot, not a permit interpretation.
Open question
2021 IRC, effective September 30, 2024
The county’s official adopted-codes page lists the edition and exclusions, but no adopted appendices. The status of 2021 IRC Appendix F—the radon-control-methods appendix—could not be verified from the public page.
Official county adopted-codes pageverified live
Do not assume.
Ask whether Appendix F was adopted before representing radon-resistant construction as required.
03
Buyer brief
What the code split means in practice
Disclosure is about what the seller knows. Testing is how the buyer learns what the house is doing now.
Tennessee’s Residential Property Condition Disclosure form explicitly names radon gas among environmental hazards and advises buyers to include radon in inspection contingencies.9 The form is knowledge-based, not a substitute for inspection.10
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Identify the governing jurisdiction
“Williamson County” is not enough. Confirm whether the home is inside Franklin, Brentwood, or the unincorporated county before making claims about code-required radon features.
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Test even when a passive system is present
Radon-resistant construction reduces entry pathways; it does not certify a measured indoor result. In this Zone 1 county, a post-construction test closes the loop.4
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Do not treat “no disclosure” as “no radon”
Tennessee law includes disclosure-form exemptions for certain new construction with a written warranty and for property the owner has not occupied within the prior three years.9
04
Radon testing resources
Test, understand and act
A test result is useful when the next step is easy to find.
Use these public-health resources to get a test, speak with a specialist or find a certified radon professional.
If your result comes back high
- 1-800-644-6999 — the Fix-It Hotline, for general guidance on lowering radon in your home.
Learn more
Why it matters
- Radon causes about 21,000 U.S. lung cancer deaths a year — the second-leading cause overall and the leading cause among people who never smoked.
- Smoking plus radon raises the risk roughly ~9×.
- About 1 in 15 homes has high radon.
- Retest at least every 2 years if you have a mitigation system, and after renovations or changes to how you use the lowest floor. EPA recommends taking action at 4 pCi/L and considering it between 2 and 4.
Hotline information: EPA and CDC. Health statistics and testing cadence: American Lung Association.13
05
Local rules
What was—and was not—found
No county- or Franklin-specific radon rule surfaced for public buildings, schools or transactions.
That is a research result, not proof that no unpublished policy exists. The statewide school posture documented in a 2018 review is encouragement rather than a testing, retesting or mitigation mandate.7
Public buildings
No Williamson County or Franklin counterpart to Metro Nashville’s 1989 public-building radon regulation was found. Metro’s rule is a useful contrast, not a Williamson rule.8
Schools
No Williamson County Schools radon-testing policy was found. TDEC’s state program provides technical information, while the reviewed statewide policy describes testing as encouraged.7
How do I find a certified radon professional in Williamson County?
Tennessee doesn't license radon testers or mitigators, so national certification is the best way to check qualifications. The Tennessee Radon Program points residents to two directories: search them by ZIP code and widen the radius if nothing is listed nearby.
We don't recommend or rank companies. Before you hire, check the certification number in the directory yourself and ask for a follow-up test after any system is installed. Questions to ask a radon professional.
06
Sources
Links and verification notes
Primary sources lead. Secondary sources are labeled.
- Tennessee Radon Testing dashboard — 2022–2023 county snapshot; values manually transcribed October 13–14, 2026. official dashboard
- Williamson County adopted codes — live page verified October 14, 2026. official
- City of Franklin adopted codes — indexed text; live access was blocked by an Akamai wall during research. official · index
- 2024 IRC Appendix BE — includes Williamson in Tennessee’s Zone 1 county table. code publisher
- Radon Testing Disparity Report for Tennessee — mirror of the 2022 report; separate 10-year dataset. secondary mirror
- NRSB Find a Professional and NRPP Professional Search — searches verified live October 14, 2026.
- Radon in Schools: A Brief Review of State Laws and Regulations — 2018 fifty-state review.
- Metro Nashville Board of Health Regulation S088-526 — 1989 public-buildings contrast. official
- Tennessee Residential Property Condition Disclosure RF 201 — form copy cited in the research.
- Tenn. Code Ann. § 66-5-210 (disclosure form) — explanation of the known-condition standard. secondary
- Brentwood ordinance text, Code §14-66 — public index text quotes the 2018 IRC “including appendices E and F.” official document · index
- TDEC Radon Program — statewide program and homeowner test-kit information. official
- American Lung Association: Radon — health statistics, testing cadence and the free Radon Basics course. public health