Land Surveyors in Seattle, WA

Two Grids That Never Agreed

Seattle's property lines start with an argument. When Arthur Denny, Carson Boren and Doc Maynard filed their plats on May 23, 1853, Denny and Boren ran their streets parallel to the Elliott Bay shoreline while Maynard held to the compass. The seam is still visible along Yesler Way, where the two grids collide at odd angles. Maynard's north-south orientation is the one that spread across the rest of the city and the county, but downtown and Belltown parcels still carry the older skew, and the regrades that later lowered Denny Hill moved street grades by many feet. Retracing a lot in those areas means reconciling old plat calls with ground that no longer sits where it did when the monuments were set.

Slopes the City Maps as Critical

The Seattle Department of Construction and Inspections (SDCI) administers the Environmentally Critical Areas code, and about 8.4 percent of the city is mapped as slide-prone. Deep-seated landslide ground is recorded in southwest Magnolia, the Queen Anne slopes, Alki and Admiral Way in West Seattle, west Beacon Hill, Interlaken, Madrona and Pigeon Point. On a lot touching one of those designations, SDCI review expects a plan that shows the slope itself - contours, the top and toe, and the buffer - before any addition, DADU or new house is designed around it.

Middle Housing and the Lowlands

The state's HB 1110 required Seattle to allow duplexes through sixplexes, cottages and townhouses in what used to be single-family zoning, and the 2025 code rewrite renamed those areas Neighborhood Residential. Townhouse rows built for separate sale have long been divided through the unit lot subdivision process, and more neighbourhoods are now candidates for that kind of redevelopment. At the other end of the city, South Park sits on the Duwamish floodplain; on December 27, 2022 a king tide and heavy rain pushed the river into homes and streets there.

Typical Seattle Orders

Redevelopment of a city lot usually opens with a topographic survey for the architect and a boundary survey to fix the lines on the skewed or regraded blocks. Townhouse projects go on to a short plat or unit lot subdivision, then construction staking for the foundations. Owners reshaping a side yard between neighbours use a lot boundary adjustment through SDCI. Commercial acquisitions downtown call for an ALTA/NSPS survey, South Park and the Duwamish corridor produce elevation certificate requests, and finished buildings are documented with an as-built survey. Nearby, we also cover Shoreline and Mercer Island.

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