Washington Radon Mitigation Cost by County, Foundation, and Rules
Compare typical local price ranges for basement, slab, and crawl space systems. Use the state-level ranges first, then open your county when you need a local estimate after a confirmed radon result.
Fastest Start
Use ZIP Instead of Scrolling
If you know the property ZIP, jump straight to the right county estimate instead of browsing the full state list.
Cost Basics
Foundation & Result Ranges
Use the national cost guide if you need basement, slab, crawl-space, or 4.0+ result context first.
Validate the Risk
Check WA Radon Levels
If you do not have a confirmed radon result yet, review EPA zone context before you compare mitigation pricing.
Browse Counties
Jump to County Pricing
Open your county if you already know the area and just need a local basement, slab, or crawl-space price range.
Official State Resource
Washington radon program and rules
Use the state program link to verify local radon guidance, disclosure language, and contractor credential expectations before you act on an estimate.
Disclosure rule tracked
Washington requires sellers to complete a Seller Disclosure Statement (Form 17) covering environmental hazards.
Credential note
Washington does not require specific radon licensing.
WA Cost Starting Point
Washington cost range by foundation
Basement
$975-$1727
Use this when the home has a basement or lowest-level slab that supports a standard sub-slab suction system.
Slab-on-Grade
$918-$1612
Slab homes can price differently when finished space, routing, or core drilling complicates the system path.
Crawl Space
$1490-$2700
Crawl-space jobs can move higher when vapor-barrier sealing, access, and sub-membrane suction add labor.
State rules that can change the quote
Disclosure: Required or commonly expected in this state context. Washington requires sellers to complete a Seller Disclosure Statement (Form 17) covering environmental hazards.
Mitigation licensing: No state-specific mitigation license premium is modeled. Washington does not require specific radon licensing.
EPA zone mix in Washington
7
Zone 1
14
Zone 2
18
Zone 3
39 classified counties are used for state-level risk context. EPA zones do not replace a home test, but they help explain why county pages and confirmed 4.0+ results matter before comparing quotes.
Local cost guides
Washington evidence-backed cost route
The cost directory follows the same eligibility rule as the county cost pages themselves. State hubs, sitemap candidates, and internal links point at pages Google can actually index.
39
Listed
39
Evidence
39
Measured
Best county pages to open first
Spokane County
Demand cohort local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 41.4% 4.0+
Spokane County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 41.4% 4.0+ with a local housing base of 225,044 units and a modeled planning range of $975-$1727.
Clark County
Evidence-backed local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 25.1% 4.0+
Clark County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 25.1% 4.0+ with a local housing base of 196,557 units and a modeled planning range of $975-$1727.
Kitsap County
Demand cohort local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 4.9% 4.0+
Kitsap County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 4.9% 4.0+ with a local housing base of 113,930 units and a modeled planning range of $975-$1727.
Benton County
Evidence-backed local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 19.5% 4.0+
Benton County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 19.5% 4.0+ with a local housing base of 80,421 units and a modeled planning range of $975-$1727.
Stevens County
Cost eligible local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 36.2% 4.0+
Stevens County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 36.2% 4.0+ with a local housing base of 22,312 units and a modeled planning range of $975-$1727.
Okanogan County
Cost eligible local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 35% 4.0+
Okanogan County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 35% 4.0+ with a local housing base of 21,917 units and a modeled planning range of $975-$1727.
Whitman County
Demand cohort local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 22.4% 4.0+
Whitman County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 22.4% 4.0+ with a local housing base of 20,974 units and a modeled planning range of $975-$1727.
San Juan County
Demand cohort local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 0% 4.0+
San Juan County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 0% 4.0+ with a local housing base of 13,851 units and a modeled planning range of $975-$1727.
King County
Evidence-backed local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 2.6% 4.0+
King County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 2.6% 4.0+ with a local housing base of 972,821 units and a modeled planning range of $975-$1727.
Thurston County
Evidence-backed local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 10.1% 4.0+
Thurston County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 10.1% 4.0+ with a local housing base of 121,682 units and a modeled planning range of $975-$1727.
Walla Walla County
Evidence-backed local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 16.4% 4.0+
Walla Walla County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 16.4% 4.0+ with a local housing base of 25,032 units and a modeled planning range of $975-$1727.
Pend Oreille County
Cost eligible local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 63.2% 4.0+
Pend Oreille County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 63.2% 4.0+ with a local housing base of 7,993 units and a modeled planning range of $975-$1727.
Skamania County
Cost eligible local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 39.7% 4.0+
Skamania County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 39.7% 4.0+ with a local housing base of 5,830 units and a modeled planning range of $975-$1727.
Pierce County
Evidence-backed local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 4.9% 4.0+
Pierce County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 4.9% 4.0+ with a local housing base of 360,816 units and a modeled planning range of $975-$1727.
Snohomish County
Evidence-backed local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 2.3% 4.0+
Snohomish County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 2.3% 4.0+ with a local housing base of 323,438 units and a modeled planning range of $975-$1727.
Grant County
Evidence-backed local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 23.5% 4.0+
Grant County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 23.5% 4.0+ with a local housing base of 38,851 units and a modeled planning range of $975-$1727.
Douglas County
Cost eligible local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 35.7% 4.0+
Douglas County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 35.7% 4.0+ with a local housing base of 17,438 units and a modeled planning range of $975-$1727.
Klickitat County
Cost eligible local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 41.4% 4.0+
Klickitat County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 41.4% 4.0+ with a local housing base of 10,602 units and a modeled planning range of $975-$1727.
Ferry County
Cost eligible local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 25% 4.0+
Ferry County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 25% 4.0+ with a local housing base of 4,100 units and a modeled planning range of $975-$1727.
Whatcom County
Evidence-backed local evidence
$975-$1727
CDC EPHT Network Radon Tests from Labs: 5.4% 4.0+
Whatcom County is a strong cost page because it pairs CDC EPHT Network Radon Tests from Labs: 5.4% 4.0+ with a local housing base of 100,394 units and a modeled planning range of $975-$1727.
County estimates
Open a Washington county page for local pricing
County pages narrow the state range with local EPA zone context, housing data, state rules, and the foundation scenario you choose.
Why Does Cost Vary in Washington?
Price ranges across Washington move with local labor rates, permit friction, roofline routing, and foundation type. County pages narrow this down for homeowners comparing basement, slab, or crawl space mitigation after a confirmed radon reading.