Buying Land in Snohomish County, Washington

A fast-growing exurban county planning for hundreds of thousands more residents

Snohomish County anchors the northern edge of the greater Seattle metro area, and its growth trajectory is a defining fact for any land buyer here. County population is estimated at roughly 880,000 in 2026, and the county's own December 2024 Comprehensive Plan update -- which plans through 2044 -- forecasts a medium-range addition of about 308,000 more residents over that period. As one of the original seven counties the 1990 Growth Management Act required to fully plan (along with Clark, King, Kitsap, Pierce, Thurston, and Whatcom), Snohomish has to direct that growth into designated Urban Growth Areas under a regionally coordinated strategy centered on transit-oriented infill, with a specific focus on the large unincorporated urban pocket between Lynnwood, Everett, and Mill Creek, and on the Paine Field/Boeing Everett manufacturing area as an employment growth center. Snohomish is also one of only seven Washington counties required to file periodic Buildable Lands reports, which compare actual development against the capacity the county planned for -- a check the state uses to see whether adopted zoning is producing the growth pattern the comprehensive plan assumed. For a buyer, the practical upshot is that a parcel's status inside or outside the county's UGA boundary, and its specific zoning designation within that boundary, does real legal work here and shouldn't be assumed from a listing description alone.

Steep-slope development rules after the 2014 Oso landslide

On March 22, 2014, a massive landslide off State Route 530 near the community of Oso, between Arlington and Darrington, killed 43 people and remains the deadliest landslide in U.S. history -- and it happened in Snohomish County. In its aftermath, the county imposed temporary building bans in and around the slide area and, more durably, development in geologically hazardous areas countywide is now governed by Snohomish County Code Chapter 30.62B, adopted under the state's Growth Management Act 'best available science' mandate. Rather than a single flat setback distance from a steep slope, the county's approach ties required setbacks to the height of the slope itself, using different measurement rules from the top of the slope than from the bottom -- an approach similar to the International Building Code's slope-setback method. Reporting published roughly a year after the disaster found the county had not made sweeping changes to its underlying steep-slope development rules despite the scale of the tragedy, so this slope-height-based framework, not a newer standard, is what still governs today.

For a buyer evaluating any Snohomish County parcel with visible slope, a nearby bluff, or land in or near the Stillaguamish River valley corridor between Arlington and Darrington, a geotechnical review addressing SCC 30.62B's geologically hazardous areas standard should be budgeted for as a real step in due diligence, not treated as an unlikely formality.

Rural Cluster Subdivision: a real density tool for larger rural tracts

For anyone looking at a larger rural parcel with subdivision potential, Snohomish County's Rural Cluster Subdivision technique is worth understanding specifically. It lets a landowner group new lots into a compact cluster -- with an average lot size as small as 7,200 square feet, well below typical rural minimums -- as long as at least 45% of the overall site is preserved as designated open space, and each resulting lot still independently satisfies Snohomish Health District's on-site sewage disposal rules. In exchange, the technique earns a density bonus of 15% to 35%, scaled to how much open space is committed. It's available outright in the Forestry (F), Forestry and Recreation (F&R), Mineral Conservation (MC), and Rural Resource Transition 10-Acre (RRT-10) zones, and in more limited circumstances in the Rural Five Acre (R-5), Rural Conservation (RC), and Rural Diversification (RD) zones. Anyone evaluating a large rural tract purely as a single homesite, rather than a future subdivision, should still confirm the base zoning's standard minimum lot size and RUTA (Rural Urban Transitional Area) rules separately, since cluster provisions are an optional overlay, not the default.