Washington's rain-country climate shapes its housing risks more than almost any other factor: chronic moisture intrusion, moss-eaten roofs, crawl spaces that never fully dry, and drainage systems working year-round. Add meaningful earthquake exposure in the Puget Sound region and a licensed, regulated inspection profession, and Washington buyers face a distinctive checklist. This guide covers the state's Form 17 disclosure law, who licenses home inspectors here, the regional hazards to prioritize, and what an inspection costs.
Washington's Form 17: the Seller Disclosure Statement
Washington law (RCW 64.06) requires sellers of improved residential real property to complete and deliver a Seller Disclosure Statement — universally known as Form 17 — to the buyer. It has been required since January 1, 1995, and the current version runs six pages. Under the standard transaction timeline, the seller must deliver the completed form within five business days after mutual acceptance of the purchase agreement, and the buyer then has three business days to rescind the agreement after receiving it.
Form 17 asks the seller to answer "Yes," "No," or "Don't Know" to questions about known conditions, with written explanations required for every "Yes." Its sections cover title and legal matters, water source and drainage, sewer or septic systems, structural components, home systems and fixtures, and environmental concerns — plus a catch-all question for anything material not otherwise listed.
Sellers disclose based on actual knowledge — Form 17 is not a warranty of condition. Limited exemptions exist (foreclosure sales, gifts to close family, divorce-related transfers, estate and bankruptcy trustees, and cases where the buyer waives receipt, though the environmental section generally cannot be waived). Read Form 17 before your inspection and hand it to your inspector: a "yes" on past water intrusion tells them exactly where to spend their time.
Who licenses Washington home inspectors: the Department of Licensing
Washington has required home-inspector licensure since 2009. The Washington State Department of Licensing (DOL) administers the program under the Home Inspector Act (RCW 18.280), overseen by the Home Inspector Advisory Licensing Board: 120 hours of classroom instruction, 40 hours of field training plus supervised inspections, both the national and state exams, and 24 hours of continuing education every two years. Inspecting without a license can draw fines and legal action.
One Washington-specific wrinkle: pest inspections are regulated separately. The Department of Agriculture licenses Structural Pest Inspectors who perform complete wood-destroying-organism inspections. A licensed home inspector must report wood decay and conditions conducive to it, but cannot formally inspect for wood-destroying insects without also holding the pest inspector license. If the home has moisture problems, a separate pest inspection is often worth ordering alongside the general one.
Even in a licensed state, vet your inspector: confirm the DOL license is current, ask for a sample report, confirm errors-and-omissions and liability insurance, and favor inspectors with deep experience in older Puget Sound housing.
The five Washington hazards your inspection must cover
1. Moisture intrusion — the master risk
Western Washington's months of wind-driven rain find every weakness in a building envelope: failed flashing around windows and doors, deteriorated sealant, cracked stucco, and siding installed too close to grade. The damage hides inside walls long before it shows on paint. Your inspector should probe suspicious areas with a moisture meter, check the attic for roof leaks, and look for the tell-tale signs of past intrusion — fresh caulk over old stains, mismatched siding sections, and efflorescence on foundation walls. Homes with stucco or EIFS cladding deserve extra scrutiny; trapped moisture behind these systems is a notorious and expensive Pacific Northwest problem.
2. Roofs, moss, and gutters
Composition shingle roofs in the Puget Sound region grow moss aggressively, and moss lifts shingles, traps moisture, and shortens roof life. During the inspection, note the roof's age, moss coverage, and whether valleys and gutters are clear — clogged gutters in a November downpour overflow directly into siding and foundations. Cedar shake roofs, common on older Northwest homes, rot from the underside when ventilation is poor. Ask about the roof's age and replacement history on Form 17, and for roofs past 15–20 years, consider a roofer's opinion in addition to the general inspection. Replacement for a typical single-family roof runs $10,000 to $20,000 or more.
3. Crawl spaces and drainage
A huge share of Washington homes are built over crawl spaces rather than basements, and crawl spaces are where the region's moisture problems concentrate: standing water, failed vapor barriers, sagging insulation, fungal growth on joists, and rodent intrusion. A thorough inspector physically enters the crawl space — not just peers through the hatch. Outside, the inspection should trace the whole drainage path: gutters to downspouts to extensions or drains, and grading sloping away from the foundation. In a state where it rains for half the year, drainage is a system, not a feature — verify the whole chain.
4. Seismic risk in the Puget Sound region
Western Washington sits in one of the most seismically active zones in the country, exposed both to the Cascadia subduction zone offshore and to shallow crustal faults like the Seattle fault beneath the metro area. Older homes — particularly pre-1980s houses with unbolted sill plates, unbraced cripple walls, and unreinforced masonry chimneys — are the most vulnerable. Your inspector can note visible seismic weaknesses: a house not bolted to its foundation, a tall unbraced chimney, a garage with living space above and inadequate shear walls. Full seismic retrofitting typically costs $3,000 to $7,000 for a straightforward house and is one of the highest-value safety upgrades a buyer can negotiate or plan. Also confirm the home is not in a mapped landslide or liquefaction zone.
5. Septic systems and oil tanks
Rural and semi-rural Washington — the islands, the peninsula, and the exurbs — runs heavily on septic systems, and many counties require septic inspections at property transfer. A general home inspection does not evaluate a septic system; order a dedicated septic inspection ($350–$800+) with tank pumping and drain-field assessment. Separately, older homes may have decommissioned underground heating-oil tanks, which are an environmental liability if they leak — Form 17's environmental section asks about tanks. If records are murky, a tank sweep ($150–$300) is cheap insurance.
What a Washington inspection costs — and which add-ons to buy
A standard general home inspection in Washington typically runs $400 to $700, with Seattle-metro inspections commonly $450 to $700 and smaller or eastern-Washington markets somewhat less. Inspections usually take two to four hours.
Add-ons that earn their keep in Washington:
- Sewer scope — roughly $150 to $300. Older Seattle and Tacoma neighborhoods have aging clay and concrete side sewers invaded by roots; replacement costs $8,000 to $15,000+.
- Structural pest (WDO) inspection — roughly $100 to $200 by a Department of Agriculture–licensed pest inspector. Worth it wherever moisture or wood-to-ground contact shows up.
- Mold and moisture diagnostics — roughly $200 to $500 when the inspection finds active intrusion or fungal growth.
- Septic inspection — roughly $350 to $800+ on septic-served properties; often required at transfer by the county.
- Oil tank sweep — roughly $150 to $300 for pre-1980s homes with unclear heating history.
- Radon test — roughly $125 to $200. Radon is less of a headline risk in western Washington than in the east of the state, but testing is inexpensive and worth doing, especially with below-grade living space.
What this guide does not cover — and when to hire a professional
This guide explains Washington's disclosure law and rain-country inspection priorities, but it is not legal, engineering, or environmental advice. It does not cover purchase-contract contingencies, earnest-money strategy, shoreline and critical-areas regulations (which can sharply limit what you may build or remodel on waterfront and steep-slope lots — check with the city or county, not just the inspector), or well-water rights on rural properties. A general home inspection is a visual, non-invasive survey: inspectors do not open walls, certify structures, or sample for every contaminant. Bring in a specialist when the inspection flags active water intrusion or suspected envelope failure, foundation cracking or settlement, seismic vulnerabilities you want quantified, a failing or unknown septic system, or suspected oil-tank or contamination issues.
Frequently asked questions
What is Form 17 in Washington?
Form 17 is Washington's legally required Seller Disclosure Statement (RCW 64.06), in use since 1995. Sellers of improved residential property must deliver the completed six-page form within five business days after mutual acceptance, and buyers get three business days to rescind after receiving it.
Are home inspectors licensed in Washington?
Yes — since 2009. The Department of Licensing administers the program under RCW 18.280, requiring 120 hours of education, 40 hours of field training, both the national and state exams, and 24 hours of continuing education every two years. Verify any inspector's license with DOL before hiring. Pest inspectors are licensed separately by the Department of Agriculture.
What does a home inspection cost in Washington?
A standard inspection typically costs $400 to $700 — $450 to $700 in the Seattle metro, less in smaller markets. Common add-ons: sewer scope ($150–$300), pest inspection ($100–$200), mold/moisture diagnostics ($200–$500), septic inspection ($350–$800+), and oil tank sweep ($150–$300).
How concerned should I be about earthquakes when buying in the Seattle area?
Take it seriously but practically. The Puget Sound region faces real seismic risk from the Cascadia subduction zone and local faults. Have the inspector note visible vulnerabilities — unbolted foundations, unbraced cripple walls, tall masonry chimneys — and price a retrofit ($3,000–$7,000 for a typical house).
Do I need a separate inspection for the crawl space?
Not usually as a separate hire — a good general inspector physically enters the crawl space and reports on water, vapor barriers, insulation, fungal growth, and pests. But if the general inspection finds active moisture or fungal problems, follow up with a moisture-intrusion specialist before your contingency expires.