Clyde Hill: Middle Housing and ADU Regulations Update

In response to a series of 2023 legislative mandates from Washington State, the City of Clyde Hill has successfully updated its local development regulations to address the requirements for middle housing, accessory dwelling units (ADUs), and unit lot subdivisions. This comprehensive effort, completed in June 2025, was driven by three key bills: HB 1110, which requires cities to allow more than one housing unit per lot in single-family zones; HB 1337, which mandates the allowance of at least two ADUs per lot; and HB 5258, which requires cities to permit the subdivision of lots to allow for separate ownership of these units. The city's primary goal throughout this process was to meet the state-level requirements while carefully preserving the existing character and aesthetic of its neighborhoods, a preference that was strongly expressed by residents during the city's 2024 Comprehensive Plan update.

Clyde Hill's specific approach to the new regulations is a testament to this balancing act. To comply with the state's mandate for increased housing diversity, the city's Middle Housing Ordinance permits the construction of two cottage homes or a single-family home plus up to two ADUs on most residential lots. Cottage homes are defined as two smaller single-family homes that share a common open space. This decision represents a significant change from the city’s previous code, which only allowed for one single-family home and a single ADU. Notably, the city chose to limit allowable middle housing types to only ADUs and cottage homes, deliberately excluding attached duplexes or townhomes to maintain the current visual and structural feel of its residential areas. These new housing types are also required to adhere to the existing regulations for building size, height, and setbacks, ensuring consistency with the surrounding neighborhood.

Furthermore, the new regulations incorporate unit lot subdivision as required by state law. This critical update allows for the separate sale and ownership of ADUs or cottage homes on lots larger than 20,000 square feet, with common areas of the parent lot managed by a homeowners association or similar agreement. While Clyde Hill's minimum lot size for standard single-family homes remains at 20,000 square feet, the new code provides a path for creating smaller, more attainable unit lots for middle housing. This provides a new avenue for home ownership within the community. The city engaged in a public and transparent process, holding community discussions and public hearings to gather resident feedback before the final adoption of the ordinance on June 10, 2025, just weeks ahead of the state's deadline. The result is a regulatory framework that both respects state law and honors the community’s unique identity and preferences.