Short Plat & Unit Lot Subdivision in Seattle, WA

One Lot Becoming Several

A short plat is Washington's streamlined process for dividing land into a small number of lots. State law, RCW 58.17, sets the default at four and lets a city raise that ceiling to nine by ordinance; larger divisions go through a full long plat. In Seattle a short subdivision is reviewed by the Seattle Department of Construction and Inspections as a land use decision, with public notice and an opportunity to comment before the director decides. Other cities run their own versions: Bellevue, Kirkland, Shoreline and Kent each have their own codes, lot standards and application checklists, so the same idea is assembled differently depending on which side of a city limit the parcel sits.

Unit Lot Subdivision and Middle Housing

Much of the dividing happening now is not a house lot becoming two house lots. It is a single parcel redeveloped as a row of townhouses or a cluster of cottages, each sold with the ground beneath it. Seattle handles that through unit lot subdivision under SMC 23.24.045, where development standards apply to the parent lot as a whole while each unit lot is conveyed separately, and the plat is usually reviewed alongside or after the building permit for the homes themselves. Washington's 2023 middle-housing law, HB 1110, requires cities above certain population thresholds to allow several units on lots once zoned for a single house, which widens where this kind of project is possible across the region's residential neighborhoods.

The Surveyor's Share of the Application

The process starts with a boundary survey and a topographic survey of the parent parcel, because proposed lots, access, utility routes and any critical-area buffers are all drawn over that base. From there we prepare the plat drawing and the legal descriptions for each new lot and for shared access and utility easements, revise them through review comments, and set the new lot corners in the ground. The approved plat is recorded with King County, and it becomes the document every future owner and surveyor relies on.

What Stays With the Design Team

Whether the zoning allows the lot count you have in mind, how the units are laid out, drainage design and utility capacity belong to your architect, civil engineer and the reviewing city. We work alongside them, not in place of them. Where the goal is only to shift an existing line between two parcels rather than create new lots, a lot boundary adjustment is the simpler route. Where unit lot lines are meant to follow shared walls, an as-built survey confirms where those walls actually went.

How long does it take? Governed by the city's review timeline rather than field work. The survey is usually ready long before the application is approved.

Frequently Asked Questions