What does it mean when a seller checks "unknown" on the one form that's supposed to tell you what's wrong with a house?
In Washington, it means almost nothing changes for you as a buyer. The law that governs Form 17, the state's standard seller disclosure statement, only requires sellers to report what they actually know. If a seller bought their Hough bungalow in 2009 and the furnace was already running on natural gas, they can honestly write "unknown" next to the question about underground fuel tanks, and that answer is not a lie. It is also not protection. The gap between what a disclosure form legally requires and what it actually tells you is where most of the expensive surprises in Vancouver's older neighborhoods live, and it is a gap that changes shape depending on which decade your house was built in and which part of the city it sits in.
Four Housing Booms Stacked Under the Same City Limits
Vancouver did not grow in one steady wave. It grew in bursts, and each burst left a distinct layer of construction still standing today.
The Hough neighborhood, just northwest of downtown, holds the largest surviving collection of pre-World War II housing in the city, built primarily between 1890 and 1945 in a mix of Craftsman bungalows, four-squares, and Victorians. Much of it was listed on the Washington Heritage Register in 2003. A few blocks over, Arnada carries the same early-1900s housing stock, much of it still running on original galvanized or cast-iron plumbing.
A different boom shows up in Fruit Valley and Harney Heights, both built up rapidly during World War II to house Kaiser shipyard workers. Fruit Valley, the city's largest neighborhood by land area, sits next to the Port of Vancouver and Vancouver Lake and still carries the tightly built wartime housing from that era. Hudson's Bay, closer to downtown, mixes those same World War II-era homes with the restored Officers Row residences on the National Register of Historic Places.
Then there is everything built after, stretching into growing areas like Felida and Cascade Park, where newer subdivisions carry none of the wartime or Craftsman-era systems at all.
None of this is trivia. It maps directly onto the specific risks an inspector will flag, because Vancouver's housing eras correspond to different materials that were standard practice at the time and are now known liabilities.
The Ground Under Every One of Those Houses Is the Same. The Risk Isn't.
Radon is where the disconnect between a county-wide label and an individual house shows up most clearly. The Environmental Protection Agency classifies all of Clark County as Zone 1, its highest radon potential category. The source is geological: granite deposits carrying uranium were swept down the Columbia River Gorge by the Missoula Floods roughly 13,000 years ago, and as that uranium decays it still produces radon gas that seeps up through soil across the county today. Estimates put the share of Clark County homes exceeding the EPA's recommended action level at around one in four.
A single county-wide zone number sounds like it should apply evenly, but a geological survey of indoor radon distribution across Clark County found that risk varies enough by zip code that not one zip code in the county came back classified as low potential, while some came back moderate and others high. Health officials in the county have also noted that radon levels tend to run higher in areas closer to the Columbia River. So the honest reading of "Zone 1" is not "every house here has a problem." It is "no house here gets to skip the test," because the zone tells you the county is elevated, not what your specific lot, foundation, and crawlspace conditions add up to.
That distinction matters because Washington does not require radon testing as a condition of sale. What it requires is disclosure of known material facts, and radon falls under the environmental section of Form 17 alongside asbestos, lead paint, and fuel storage tanks. A seller who never tested has nothing to disclose. The absence of a red flag on the form is not the same as the absence of radon in the house.
What "Unknown" Actually Protects You From, and What It Doesn't
Washington's Seller Disclosure Act, codified at RCW 64.06, gives buyers a specific and short window to act. Once a seller delivers Form 17, the buyer has three business days to review it and, if they choose, rescind the purchase agreement in writing. Miss that window without objecting and the disclosure is deemed accepted.
There is a second layer built into the statute that matters more than most buyers realize. If a seller answers "yes" to any question in the form's environmental section, the buyer cannot waive their right to receive the disclosure statement at all. That protection exists specifically to stop a seller from burying a known hazard and having the buyer sign it away unknowingly. But that rule only triggers on a "yes." An "unknown" answer, which is legally distinct from a "yes" and just as legally distinct from a "no," does not activate it. A seller who genuinely never checked their crawlspace for a buried oil tank, and therefore checks "unknown," has not disclosed a hazard, has not lied, and has not given the buyer the extra protection that a "yes" would have triggered. The form did its job. It just didn't tell you anything.
This is why the real protection for a buyer in one of Vancouver's older neighborhoods is not the disclosure form itself. It is the inspection contingency that sits alongside it, typically running five to ten business days under the standard NWMLS purchase agreement, during which a buyer can add sub-inspections by addendum: a sewer scope, a radon test, an oil tank sweep, a wiring evaluation. Those are the tools that answer questions Form 17 was never built to answer.
Matching the Era to the Inspection
| If your house dates to | You're likely looking at | The sub-inspection worth requesting |
|---|---|---|
| Pre-1945 (much of Hough, Arnada) | Original cast-iron or galvanized plumbing, possible knob-and-tube wiring, higher odds of a legacy oil furnace | Sewer scope, oil tank sweep, wiring evaluation |
| 1940s (Fruit Valley, Harney Heights, parts of Hudson's Bay) | Wartime shipyard-era construction, aging original systems | Sewer scope, radon test, general systems review |
| 1960s-1970s | Aluminum branch wiring (common once copper prices rose), galvanized pipe | Wiring evaluation, radon test |
| 1978-1995 | Polybutylene piping, a known issue in Clark County homes from this window, prone to cracking under chlorinated city water | Plumbing material inspection, radon test |
| Newer construction (Felida, Cascade Park, and beyond) | Modern PEX plumbing and updated wiring as a baseline | Radon test still recommended, since the zone applies regardless of build year |
Radon testing belongs on every row of that table, new construction included, because the gas comes from the soil, not the building materials.
What the Add-On Inspections Actually Cost
A radon mitigation system, typically a sub-slab depressurization setup, runs about $800 to $2,500 installed, and one industry estimate suggests that more than 80 percent of sellers who get a high radon reading during a transaction end up negotiating some kind of credit or price adjustment rather than walking away from the deal. An oil tank sweep, usually a magnetic or ground-penetrating survey performed by a specialized contractor, produces a written certificate either way, and is a small line item next to what an undocumented tank can cost later if a lender or insurer finds out about it after closing. Rewiring a house of roughly 1,500 square feet to remove knob-and-tube or aluminum wiring can run $8,000 to $15,000, plus another $2,000 to $4,000 if the electrical panel also needs an upgrade to 200 amps. Full-home repiping in the Vancouver market has been estimated in a 2026 cost analysis at roughly $1,700 to $17,000 or more, depending heavily on pipe material, home size, and crawlspace access, and Clark County saw a reminder of what aging pipe can cost during the 2024 arctic blast, when burst pipes hit homes across the county.
None of these numbers are reasons to avoid an older Vancouver home. They are numbers worth having in hand before you write an offer, because they are exactly what gets negotiated once an inspection turns up a finding the disclosure form never mentioned.
The Sequence That Actually Protects You
- Identify your house's construction era before you write an offer, using the neighborhood context above as a starting point.
- Request the sub-inspections that match that era as part of your inspection contingency, not as an afterthought.
- Read every "unknown" answer on Form 17 as a gap to fill with your own inspection, not as a clean bill of health.
- Get radon and any other add-on test results in writing before your inspection contingency deadline, so you have room to negotiate repairs, a credit, or a price adjustment under the standard inspection response process.
- If a seller answers "yes" to anything in the environmental section, know that you cannot waive your right to the disclosure statement itself, and treat that as a signal to look closer, not a technicality to skip past.
Frequently Asked Questions
Does Washington require a radon test before selling a home in Vancouver? No. State law requires sellers to disclose known material facts, including known or suspected radon issues, but it does not mandate testing before a sale. Many buyers order their own test during the inspection period regardless of what the disclosure form says.
If a seller checks "unknown" on Form 17, can I still walk away from the deal? Yes, but not because of the disclosure form itself. Your leverage comes from your inspection contingency and its deadline, not from the three-business-day disclosure review window, which is a separate and shorter clock tied specifically to Form 17.
How long do I have to order sub-inspections like a radon test or oil tank scan? That depends on the inspection period you negotiate in your purchase agreement, which typically runs five to ten business days from mutual acceptance. Sub-inspections are usually added by checking the appropriate box or attaching an addendum to the standard inspection contingency, so they need to be requested inside that window, not after.
If you are weighing an older home in Hough or Fruit Valley against a newer build in Felida, the disclosure form will look the same either way. What changes is which sub-inspections actually earn their cost, and that's a judgment call worth making with someone who knows the neighborhoods, not just the paperwork. Property Sisters & Co. works these Vancouver neighborhoods block by block, and can help you build an inspection strategy around the house you're actually buying or selling, not a generic checklist.
