Buying a House on a Slope in Snohomish or King County: Landslide Hazard Checks (2026)

Short answer: Before you buy a house on or near a slope in Snohomish or King County, check the state and county landslide maps, read the seller’s answers about slides, fill and drainage on the disclosure form, and find out whether a landslide covenant is recorded on the lot. If the slope looks significant, hire a geotechnical engineer or engineering geologist during your inspection period. Also price insurance: homeowners policies usually don’t cover landslides.

This is general information, not legal, engineering or insurance advice. County rules quoted here apply to unincorporated areas; cities have their own codes and records, so check with the city if the house is inside city limits.

Why it’s worth checking here

King County’s 2026 landslide guidance explains that much of the area sits on layers of silt, sand and glacial till ("hardpan") left by ice sheets. Where those layers are exposed on slopes and bluffs, they can slide, especially after heavy rain or snowmelt. DNR also notes that landslides often happen again in the same places. A view lot can be a great buy. You just want to know what’s under it before you commit.

Step 1: Check the maps

Based on: DNR Landslides page and FAQ; Snohomish County Landslide Hazard Area page; King County landslide mapping page.

How the counties define a landslide hazard area

Snohomish County (unincorporated). The county’s rules are in SCC 30.62B. Its page describes a landslide hazard area as a slope with a vertical height of 10 feet or more, plus land near it: back from the top of the slope a distance equal to its height, and out from the toe a distance equal to twice its height. Slopes of 33% or more on the parcel, or within 200 feet of the work area, call for a geotechnical evaluation when you apply for a permit.

King County (unincorporated). King County defines landslide hazard areas in KCC 21A.06.680 and sets standards in KCC 21A.24.280. Its guidance says the minimum buffer without a geological critical areas report is usually 50 feet, and the county can add more setback for slopes over 200 feet tall. A report is generally needed for development within 65 feet of the potential landslide layer on iMap. Removing vegetation from a landslide hazard area or its buffer is generally prohibited.

Why this matters to a buyer: it affects what you can build later. If you’re thinking about a deck, an addition, an ADU or a new retaining wall, ask the county or city early what the slope means for permits.

Step 2: Look for a recorded covenant

In Snohomish County, development isn’t allowed in a landslide hazard area unless there’s no other buildable spot on the lot and the code’s conditions are met. When it is allowed, the owner has to record a covenant that runs with the land before permits are issued. The county’s covenant form summarizes the geotechnical report, waives claims against the county for slide damage, and requires the owner to tell later owners about the hazard and give a prospective buyer a copy before closing.

So ask the seller and the title company whether a landslide hazard covenant, a geotechnical report, or other critical areas documents are recorded against the property, and read them before your inspection period ends.

Step 3: Read the disclosure form

The Washington seller disclosure form (Form 17) has several questions that matter on a slope:

• Flooding or drainage problems on the property.
• Any fill on the property.
• Material damage to the property from fire, wind, floods, beach movements, earthquake, expansive soils or landslides.
• Whether the property is in a designated flood plain, or contains shorelines, wetlands or other critical areas.
• Whether there has been any settling, slippage or sliding of the house or other improvements.

RCW 64.06.020 currently has two versions on the Legislature’s site: one marked effective until January 1, 2027, and one effective January 1, 2027. The questions quoted here appear in both. If your sale runs across the new year, check which form is being used.

Step 4: Walk the property for warning signs

DNR’s homeowner guide to landslides lists signs to look for. Inside: new cracks in walls or floors, doors or windows that stick, and a chimney pulling away from the wall. Outside: tilting retaining walls, cracks in the soil, trees or fences that lean, and broken utility lines. It also stresses drainage: water should be directed away from slopes, and fill shouldn’t be added near them.

A home inspector may flag some of these, but slope stability is outside a standard inspection. See what a standard home inspection covers. For a site assessment, DNR says to use a licensed geotechnical engineer or engineering geologist. Book them early, since the report has to come back before your contingencies deadline, and your earnest money is on the line if you miss it.

Step 5: Price the insurance

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Data from: Washington Office of the Insurance Commissioner landslide and earthquake insurance pages.

Ask an insurance agent for quotes before you remove contingencies. The OIC consumer line is 800-562-6900. If the lot is also near water, read our guide to buying a home in a flood zone.

FAQ

How do I check if a house is in a landslide hazard area in Snohomish County?

Start with the Snohomish County Landslide Hazard Area Map Series on the county’s Landslide Hazard Area page, and the state’s Geologic Information Portal from DNR, where you can search by address. The county says its maps are for information only and every parcel shown has to be verified. For a real answer about a specific lot, you need a geotechnical evaluation. For a house inside a city, also ask the city’s planning department.

How do I check landslide hazards for a house in King County?

Use King County iMap and turn on the Environmentally Sensitive Areas layers, and check the DNR Geologic Information Portal. King County says its landslide map does not identify actual landslide hazards on specific properties, so treat it as a screening step. King County’s critical areas rules cover unincorporated areas; cities have their own.

Does homeowners insurance cover landslides in Washington?

Usually not. The Office of the Insurance Commissioner says homeowners policies usually don’t cover land movement or landslides, and earthquake policies don’t cover landslides either. Some Difference in Conditions (DIC) policies from surplus line insurers cover landslides. Flood insurance may cover mudflows and erosion caused by water. Get quotes during your inspection period.

Do sellers have to disclose landslide problems in Washington?

The Washington seller disclosure form asks about material damage to the property from landslides, about fill, about drainage and flooding, about critical areas, and about any settling, slippage or sliding of the house or other improvements. The seller answers based on what they actually know, so read those answers closely and follow up on anything marked yes or don’t know.

Should I hire a geotechnical engineer before buying a house on a slope?

If the house is on or near a steep slope or bluff, it’s worth considering. DNR says to hire a licensed geotechnical engineer or engineering geologist for a site assessment. A standard home inspection doesn’t evaluate slope stability. Schedule it early so the report comes back before your inspection contingency ends.

Talk it through with a local agent

Peter Kim and Odigo Real Estate Club can help you pull the maps, read the disclosures, and time a geotechnical review inside your inspection period, with 25+ years combined experience, 593+ closings, and 122 five-star Zillow reviews. See our home buying services.

Odigo Real Estate Club · REAL Brokerage, WA #112064 · 16108 Ash Way, Suite 201, Lynnwood, WA 98087 · (425) 409-3823 · Mon–Sat 9 AM–6 PM, closed Sunday

Sources

• Washington State Department of Natural Resources, Landslides (recurrence, mapping methods, considering landslide risk), https://dnr.wa.gov/washington-geological-survey/geologic-hazards-and-environment/landslides , accessed Nov 2, 2026.
• Washington State Department of Natural Resources, Geologic Information Portal (Natural Hazards view with landslide layers), https://dnr.wa.gov/washington-geological-survey/publications-and-data/geologic-information-portal , accessed Nov 2, 2026.
• Washington State Department of Natural Resources, Washington Geological Survey FAQ (address search; licensed geotechnical engineer or engineering geologist for site assessments), https://dnr.wa.gov/washington-geological-survey/frequently-asked-questions , accessed Nov 2, 2026.
• Washington State Department of Natural Resources, Homeowner’s guide to landslides (warning signs inside and outside; drainage and fill), https://www.dnr.wa.gov/sites/default/files/2025-04/ger_homeowners_guide_landslides.pdf , accessed Nov 2, 2026.
• Snohomish County Planning and Development Services, Landslide Hazard Area (SCC 30.62B; 10-foot height definition; 33% slopes within 200 feet; map limits; covenant requirement), https://snohomishcountywa.gov/3681/Landslide-Hazard-Area , accessed Nov 2, 2026.
• Snohomish County Planning and Development Services, Landslide Hazard Covenant form (geotechnical report abstract, waiver, duty to inform), https://www.snohomishcountywa.gov/DocumentCenter/View/36773/Landslide-Hazard-Covenant , accessed Nov 2, 2026.
• King County Department of Local Services, Landslide hazard area guidance (February 2026) (KCC 21A.06.680 and 21A.24.280; 50-foot buffer; vegetation removal), https://cdn.kingcounty.gov/-/media/king-county/depts/local-services/permits/building-land-use-permits/l/2026-landslide-hazard-area-guidance.pdf?hash=89E252BFAC06DB5A8DE1752A11C7E579&rev=a65320a944eb424d9224ddeb41ffb4f0 , accessed Nov 2, 2026.
• King County Department of Local Services, Geological critical areas report guidance (2026) (report triggers within 65 feet), https://cdn.kingcounty.gov/-/media/king-county/depts/local-services/permits/building-land-use-permits/g/2026-geological-critical-areas-report-guidance.pdf?hash=5A0FEBC01AA92EDC56E66445916AD2AD&rev=98e293c9b4b841489cdf94860bfc6fca , accessed Nov 2, 2026.
• King County Department of Local Services, Landslide mapping (iMap layers and map limitations), https://kingcounty.gov/en/dept/local-services/buildings-property/property-research-and-maps/landslide-mapping , accessed Nov 2, 2026.
• Washington State Office of the Insurance Commissioner, Landslide insurance (homeowners exclusions, DIC policies, flood coverage for mudflows), https://www.insurance.wa.gov/insurance-resources/natural-disasters/disaster-preparedness/landslide-insurance , accessed Nov 2, 2026.
• Washington State Office of the Insurance Commissioner, Earthquake insurance (landslide exclusion; 10% to 25% deductibles), https://www.insurance.wa.gov/insurance-resources/natural-disasters/disaster-preparedness/earthquake-insurance , accessed Nov 2, 2026.
• Washington State Legislature, RCW 64.06.020 (seller disclosure statement form; version effective until Jan 1, 2027 and version effective Jan 1, 2027), https://app.leg.wa.gov/RCW/default.aspx?cite=64.06.020 , accessed Nov 2, 2026.

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