Do You Need a Radon Test in Portland or Vancouver?

Do you need a radon test when buying or selling a home in Portland or Vancouver?

No. Neither Oregon nor Washington requires a radon test as part of a home sale. Still, testing is worth considering here. Both states address local radon risk in their building codes: Oregon named Clackamas, Multnomah, and Washington counties in statute, and Washington's residential code lists Clark County as a high radon potential county. If you're buying here, a radon test is a roughly $20 to $200 decision on a $400,000 to $800,000 purchase. If you're selling, take a close look at what your state's disclosure form actually asks about radon.

By Rick Sadle | September 10, 2026

Here's some local context I think buyers and sellers should have.

Oregon law — ORS 455.365 — directs the state's building code boards to apply radon-resistant design and construction standards for new residential and public buildings in seven counties. Three of them are core Portland metro: Clackamas, Multnomah, and Washington. (The others are Baker, Hood River, Polk, and Yamhill.) The Oregon Health Authority states those standards apply to residences built after April 1, 2013.

Across the river, Washington's residential code, WAC 51-51-60101, requires jurisdictions in "high radon potential (Zone 1)" counties to adopt Appendix F radon control methods. Table AF101(1) lists exactly seven Washington counties. Clark County is one of them. That same rule also says unvented crawl spaces are not permitted in any high radon potential county.

So both sides of the Columbia are flagged in their own state's code. Neither state turned that into a testing requirement for resale homes.

For buyers, the practical point is that an optional test can still be a sensible part of your inspection.

What the disclosure forms actually ask you

When I walk sellers through the disclosure form, this is a detail I like to slow down on.

Oregon's Seller's Property Disclosure Statement is set by statute at ORS 105.464. Item 9.F asks whether any portion of the property "has been tested or treated for asbestos, formaldehyde, radon gas, lead-based paint, mold, fuel or chemical storage tanks or contaminated soil or water."

The wording matters: it asks whether the property has been tested or treated. A "No" answer isn't a radon test result.

A seller may not know the home's radon level if it has never been tested. Buyers shouldn't read a "No" as assurance that the home doesn't have radon. Sellers also need to consider the full question, which covers testing or treatment for several substances, not just radon.

Washington's Form 17, set out at RCW 64.06.020, frames it differently. Its environmental section asks whether there are "any substances, materials, or products in or on the property that may be environmental concerns, such as asbestos, formaldehyde, radon gas, lead-based paint, fuel or chemical storage tanks, or contaminated soil or water." That's a knowledge question, not a testing question — and like every Form 17 answer, it's bounded by what the seller actually knows.

Neither form requires you to get a test. If you're selling in either state, it helps to understand how Oregon's disclosure statement and Washington's Form 17 diverge before you fill either one out.

Oregon also has an information requirement: ORS 105.848 requires the Oregon Real Estate Agency to publish radon information for buyers of one- and two-family dwellings and post it on its website. That's an obligation on the agency to make information available — not a requirement that your seller hand you a radon packet at closing. You can review that information before your inspection period.

What a test costs, and why September matters

Compared with the cost of the house, testing is a small expense. Here are the options:

• Hardware-store kits: $15 to $30, per the Oregon Health Authority. Check whether lab analysis is included in that price — some kits bill for it separately.
• American Lung Association kits: $18 short-term, $30 long-term, with shipping and lab analysis included.
• A certified measurement company: costs more than a kit, but can be useful when you need results within a short inspection window. OHA specifically notes measurement companies get hired when results are needed fast — like during a 10-day inspection period.

Short-term kits sit in the home two to 90 days. Long-term kits sit 90 days or more and give you a more reliable year-round average. OHA says the best time to test is during the heating season, when homes tend to be closed up and radon can accumulate. We're heading into that window right now.

If you're a seller planning a spring listing in Alameda, Sellwood-Moreland, or out in Felida, testing this fall gives you time to understand the results and address any issues before listing. It's the same reason you might get a pre-listing inspection: having that information early gives you more time to plan.

The numbers that trigger action

EPA's action level is 4.0 pCi/L. The World Health Organization recommends mitigating at 2.7 pCi/L or above. OHA notes that there is no safe level of radon — the goal is risk reduction, not a clean bill of health.

An initial short-term result at or above 4.0 pCi/L should be followed by a second test before anyone makes a decision. Radon levels swing over the course of a year, and sometimes over a single day. That's why follow-up testing matters.

I wouldn't rely on the county map to decide whether to test a particular home. EPA says its Map of Radon Zones "should not be used to determine if individual homes need to be tested." A neighbor's low reading doesn't establish the radon level in your house.

If a test comes back high

The standard fix is sub-slab depressurization — a pipe and a continuously running fan that pull radon-laden air from beneath the foundation and vent it above the roofline. EPA says some radon reduction systems cut levels by up to 99 percent, and that most homes can be fixed for about the same cost as other common home repairs.

I'd want a contractor to look at the house before putting a number on mitigation. EPA no longer publishes a national cost range, and the real number depends on your foundation type, home size, and method. Get estimates from two or three qualified contractors.

Two Oregon-specific cautions:

1. Oregon does not regulate how companies mitigate radon. OHA maintains a list of mitigation companies with at least one technician certified by the National Radon Proficiency Program or the National Radon Safety Board. Use that list as a starting point and check references like you would for any contractor.
2. DIY is legal in Oregon, but I'd bring in a qualified professional. OHA's own guidance is that an incorrectly built system can make your radon problem worse.

In a transaction, a high result often leads to a conversation about mitigation and who will pay for it. Get a contractor's estimate and ask what warranty is included. From there, you can work through the same repair-versus-credit conversations that follow a home inspection here. Finding out late can make that conversation harder, especially when the inspection contingency is about to expire.

I'd also test a new home. A home built under Oregon's radon standards or Washington's Appendix F has passive components already in place — and OHA is clear that radon-resistant buildings can still have elevated levels, so test after construction anyway. Ask the builder directly what was installed. That's one of several questions worth asking when you're weighing new construction against a resale in this market.

Frequently Asked Questions

Is a radon test required to sell a house in Oregon or Washington?

No. The Oregon Health Authority states radon testing is not required for real estate transactions under Oregon law, and Washington has no testing mandate for resale homes either. Both states' disclosure forms reference radon, but neither obligates a seller to test.

Do I have to disclose a high radon test result?

If you have test results, bring them into the disclosure conversation. Oregon's form (ORS 105.464, item 9.F) asks whether the property has been tested or treated for radon, and Washington's Form 17 asks about substances that may be environmental concerns, naming radon gas. Answer the form accurately and share the test results and any mitigation records. Confirm your specific obligations with your attorney.

Can a buyer walk away over radon?

It depends entirely on your contract's inspection contingency, not on radon law. Radon is typically tested during the inspection period, and the outcome is negotiated like any other inspection finding — repair, credit, price adjustment, or termination if the contingency allows it.

Does a radon mitigation system hurt my home's value?

In my experience, buyers are often reassured when a seller can show what was done and provide follow-up test results. That's useful information in Clackamas, Multnomah, Washington, and Clark counties, where radon is a local concern. The system's condition and documentation matter to that conversation.

My house is new and has no basement. Do I still need to test?

Yes. OHA is explicit that elevated radon can occur in just about any house anywhere in Oregon, including new construction without a basement. Radon-resistant construction reduces risk; it doesn't guarantee a low reading.

Before you write the offer — or the listing

Here's what I tell buyers in Portland and Vancouver: make radon testing part of the inspection conversation early. Compared with a $400,000-plus purchase, it's a small expense that gives you useful information about the home.

If you're buying, arrange testing within your inspection period and leave time to review the results before your contingency deadline. If you're selling, consider testing during the coming heating season so you have time to address the results before listing.

If you're thinking through this for your own situation, I'm happy to talk through the timing, the inspection process, and what to ask a radon professional. Reach out anytime.

Sources

• ORS 455.365 — Radon mitigation standards (county list)
• ORS 105.464 — Form of seller's property disclosure statement (item 9.F)
• ORS 105.848 — Radon information for potential buyers
• WAC 51-51-60101 — Appendix F radon control methods (Table AF101(1))
• RCW 64.06.020 — Seller disclosure statement (Form 17)
• Oregon Health Authority — Radon FAQs
• U.S. EPA — Map of Radon Zones
• U.S. EPA — How much can a radon mitigation system cost?

This article covers regulatory and health-related requirements and is provided for general information. I'm a licensed real estate broker, not a CPA, an attorney, or a certified radon professional. Confirm how any of this applies to your property with a qualified radon measurement or mitigation professional and, where legal obligations are involved, with your attorney. Statutes and building code provisions change — verify current requirements before you rely on them.

About Rick Sadle
Rick Sadle is the Principal Broker and CEO of The Sadle Home Selling Team at Keller Williams Realty Professionals, serving the Portland, Oregon and Vancouver, Washington real estate markets. With more than 20 years of real estate experience, over 3,500 homes sold and more than $1 billion in team sales volume, Rick is one of the Portland area's most experienced real estate professionals. He is also a weekly real estate expert on KXL 101 FM, where he discusses the Portland and Vancouver housing markets, mortgage rates, housing trends and the economy. Rick is an Oregon-licensed Principal Broker and Washington-licensed Broker.