Radon in Prince William County, VA: Testing and Costs

EPA's 1993 Map of Radon Zones rates Prince William County Zone 2, a predicted county average indoor screening level of 2 to 4 pCi/L. Across Virginia, EPA's file puts 45 of the state's 95 counties in Zone 1, including both of its neighbors along I-95, Fairfax County to the north and Stafford County to the south.

The Census Bureau relationship file maps 15 ZIP areas to the county, all in Zone 2 counties. Virginia does not publish household test results by ZIP, and EPA reports elevated homes in every zone, so testing is the only way to know (EPA Citizen's Guide, 2016).

Most of the county's housing went up after 1980, and HomeGuide's Feb 2026 survey prices a sub-slab system for a typical basement or slab home at $1,200 to $2,000 installed.

Licensing and permits

State law: under Code of Virginia § 32.1-229.01, no one may conduct or offer radon testing or mitigation in Virginia unless listed by the National Radon Proficiency Program or the National Radon Safety Board, or meeting another proficiency measure EPA or the Board of Health accepts. VDH notes both organizations renew certificates every two years.

Standards: the same section requires testing and mitigation to follow recognized standards; VDH points to the ANSI-AARST standards EPA endorses.

Permits: Prince William County's building development office and the cities of Manassas and Manassas Park issue permits; an electrical permit may apply to the fan. HomeGuide puts radon permits at $25 to $150 where required.

Ask the installer for the certification number and the post-mitigation result.

Local conditions

The county spans two provinces. The eastern part along I-95 and the Potomac shore at Woodbridge and Dumfries sits on Coastal Plain sand and clay and the edge of the Piedmont's crystalline rock, while the west around Manassas, Gainesville and Haymarket lies in the Culpeper Basin, red shale and sandstone with diabase intrusions. Fractured shale and diabase can feed radon to soil gas.

Townhomes and single-family homes with basements dominate subdivisions along I-66, US 29 and Route 234, and many have finished lower levels, which shapes the pipe route.

The Occoquan Reservoir and Bull Run watersheds wind through the middle of the county, and homes on wooded lots near them often sit on hillsides with walk-out basements. Where part of a lower level is below grade and part is not, soil gas enters through the buried walls and slab, and suction has to reach under the whole footprint.

Fairfax County across the Occoquan River and Stafford County across Quantico Creek are both Zone 1 in EPA's file, so a county line does not mark a change in what homes should do: test.

What drives local prices

Basement townhomes: shared walls and finished basements often push the pipe through a garage or interior, an est. ×1.15 on HomeGuide's published $1,200 to $2,000 base.
Single-family homes of 2,500 sq ft or more in western subdivisions in the county: an est. ×1.25.
Slab additions and sunrooms over a basement home: a second suction area, est. ×1.5.
Permit $25 to $150 and professional retest $125 to $400 (HomeGuide).
HOA rules on exterior pipes may require routing changes (our observation).

Common jobs

Sub-slab systems in 1990s and 2000s basement homes.
Townhome systems routed through the garage.
Two-point systems where an addition sits on a slab.
Tests during relocation sales near military and federal employers.

From test to fixed, and where we cover

Step 1: test the lowest lived-in level. Step 2: at 4 pCi/L or more, get two bids from NRPP- or NRSB-listed mitigators, as Virginia law requires.

Step 3: compare them with the calculator. Step 4: retest after installation.

We cover Woodbridge, Dale City, Lake Ridge, Dumfries, Triangle, Manassas, Gainesville, Haymarket and Bristow, along I-95, I-66, US 1 and US 29.

Communities: Woodbridge, Dale City, Lake Ridge, Dumfries, Triangle, Manassas, Gainesville, Haymarket, Bristow

Before you sign

Radon is a long-term exposure risk, so compare written bids before signing (EPA Citizen's Guide). Confirm the installer's NRPP or NRSB listing first.

Questions about Prince William County

Is radon a problem in Prince William County?

EPA rates it Zone 2, but neighboring Fairfax and Stafford are Zone 1 and elevated homes occur in every zone. Test.

Does Virginia require radon mitigators to be certified?

Yes. Code of Virginia § 32.1-229.01 requires NRPP or NRSB listing for radon testing and mitigation.

How often do Virginia radon certifications renew?

VDH says both NRPP and NRSB require renewal every two years.

What does mitigation cost here?

HomeGuide's national range for a sub-slab system is $1,200 to $2,000.

Sources

Rules and fees change; confirm with the state radon office. Price your own system with the radon mitigation cost calculator, read the radon mitigation cost guide, or check any ZIP with the radon levels by ZIP tool.