In May of 2025, Governor Bob Ferguson signed a pair of bipartisan bills to ease the subdivision of urban lots for infill housing use and development. Specifically, HB 1096 requires cities to implement a process for administrative lot splitting, while SB 5559 provides clarification of required procedures for unit lot subdivision, or “ULS.” Both lot splitting and ULS procedures are designed to be more flexible and streamlined alternatives to completing a standard subdivision process.
Lot Splitting under HB 1096
Enactment of HB 1096 will add a new section to RCW 58.17, setting forth certain conditions under which local jurisdictions must approve an administrative lot-split. This legislation also requires cities to allow as many dwelling units on newly created lots as were allowed on the parent lot. Both the parent lot and the new lot must meet the jurisdiction’s minimum lot size requirements and local minimum density requirements.
Notably, cities are not required to implement the law until 2027.
Unit Lot Subdivisions under SB 5559
As a potential complement or alternative to the new “lot splitting” tool that HB 1096 officially creates, SB 5559 provides clarification and progress toward uniformity in the ULS efforts that some Washington cities and towns have already begun to implement.
Among other things, the law provides that a city or town’s ULS procedures (i) may not require any public predecision meeting or hearing, or any non-administrative design review; (ii) must apply only clear and objective standards; (iii) must be logically integrated with any other application review and approval processes that apply; and (iv) must be subject to applicable deadlines for the local government’s permit reviews and decisions.
Important Caveats in Seattle City Limits
Several factors may limit the immediate impacts of these two laws within the City of Seattle. First, under HB 1096, the City’s minimum lot size and density requirements will still apply to new projects, and projects that seek to split an existing lot into more than two new lots may still need to undergo a more rigorous administrative process or pursue alternate means of dividing the property, such as condominiumization. The legislation also provides the City with a grace period of several years for implementation of the new practice.
The City of Seattle has also signaled that it is likely to continue limiting the availability of ULS procedures, by prohibiting housing providers from using ULS procedures on attached or detached accessory dwelling units (ADUs and DADUs).
If you have questions about the impacts of this new legislation, or about the most effective way to subdivide property for your project, please contact a member of HCMP’s Real Estate or Land Use teams, including Josh Friedmann or Jesse Johnson.
The information contained in this update is provided for informational purposes only. It should not be construed as business, legal, accounting, tax, financial, investment or other advice on any matter and should not be relied upon as such.
