Washington County Radon · East Tennessee
Washington County sits in EPA Zone 1, yet no reviewed local jurisdiction has a confirmed radon-appendix adoption. New construction should not be assumed radon-ready—and every home still needs a test.
EPA zone: Zone 1Region: East TennesseeState test data: State test figures couldn't be confirmed, so they aren't shown
Yes, it can be. Washington 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.
No, not in Johnson City (Appendix Q only) or Jonesborough (no appendices). Unincorporated Washington County's current adoption wasn't confirmed. Local code details
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
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
Tennessee doesn't license radon professionals, so look for NRPP or NRSB certification. Search both national directories by ZIP code; certified professionals often serve Washington County from nearby cities. How to choose a radon professional
Johnson City adopts the 2018 IRC with Appendix Q only; Jonesborough’s reviewed 2012 IRC record lists no appendices; and the county’s only public 2012 document is still labeled “Proposed.” None confirms adoption of a radon appendix.123 That makes radon-resistant construction optional on the records available online—even in EPA’s highest-potential zone.7
Zone 1 is EPA’s highest-potential category, associated with predicted average indoor screening levels above 4 pCi/L.7 It is a planning signal—not a result for any address.
The Tennessee Radon Testing map covers 2022–2023, but Washington County’s average, median and maximum could not be read through the map’s canvas-rendered accessibility tree.8
No tooltip value is published here as Washington County’s. The pre- and post-mitigation charts stayed at Northeast Region aggregates rather than filtering to the selected county.
Appendices do not apply just because a jurisdiction adopts an IRC edition. The radon appendix must be included in the local adoption record.
Ordinance 4758-20 adopts the 2018 IRC with Appendix Q, Tiny Homes. Appendix F—the 2018 radon appendix—is absent. The city’s adopted-code page says these codes were current as of February 8, 2021.14
The reviewed Title 4 adopts the 2012 IRC “with any modifications” and lists no appendices. The town opted out of statewide residential enforcement under Ordinance 2017-06. Its present code edition needs direct confirmation.2
Johnson City has its own Building Division. Jonesborough affirmatively opted out of state residential enforcement. Washington County’s records show a county inspection program and current residential permit forms.125
Tennessee’s Fire Marshal program applies where local government has not adopted and enforced its own residential code and has not opted out. Its statewide standard is the 2018 IRC / 2018 IECC.9
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.
Tennessee’s standard property disclosure advises buyers to include radon among appropriate inspection contingencies. It does not create a standalone radon-testing mandate.14
No reviewed Washington County jurisdiction confirms adoption of its IRC radon appendix. Ask the builder which radon-resistant features were installed, then verify them.
Because Tennessee does not mandate a transaction test, buyers should negotiate a radon inspection contingency and leave time for a qualified measurement professional.
Zone 1 describes countywide potential, not a particular home. The only way to know an address’s radon level is to test that home.
Local growth raises the stakes for new-home buyers. A 2026 East Tennessean report described expanding development in Washington County, including housing growth near ETSU and Boones Creek. Those observations describe development—not radon levels—and do not change the need for property-specific testing.15
Short answers grounded in the EPA zone record, local code documents, the state dashboard review and current certification directories.
Yes. Washington County is EPA Radon Zone 1, the highest-potential category. That designation supports testing, but it cannot predict the reading in an individual home.
No reviewed jurisdiction has a confirmed radon-appendix adoption. Johnson City adopts Appendix Q only to its 2018 IRC; Jonesborough’s reviewed 2012 code lists no appendices; and the county’s public resolution is still labeled proposed.
The state dashboard’s canvas-rendered county tooltips could not be read reliably. Its pre- and post-mitigation charts remained Northeast Region aggregates, so no Washington County average, median, maximum or test count is published here.
No statewide transaction test is mandated. The state disclosure framework addresses known defects, and the standard form advises buyers to include radon among appropriate inspection contingencies.
Official records establish the local code framework. The state dashboard and professional directories are dated snapshots reviewed October 16, 2026.