Project: 28th Avenue ADU Cluster

Neighborhood: Mount Baker

Status: Completed in 2025

Building Type: Residential

# Units: 8

Missing Middle housing designed by b9 architects in Seattle, WA

Located in Seattle's Mount Baker neighborhood, the 28th Avenue ADU Cluster demonstrates how recent housing policy changes can unlock new opportunities for residential scale density while maintaining the character of Seattle’s neighborhoods. The project consists of four detached single-family homes and four accessory dwelling units (ADUs) distributed across two adjacent lots, creating eight new homes and is a great example of missing middle housing.

Each residence is approximately 1,100 - 1,200 square feet and is organized as a two-bedroom home spanning two stories above a basement level. The site plan centers around a shared courtyard that provides six off-street parking stalls, accessed from a side street to the west. By locating vehicle access and parking internally, the project preserves an active pedestrian-oriented streetscape along 28th Avenue while creating a shared open space for residents.

This development was made possible by changes to Washington State legislation in the early 2020s that expanded opportunities for ADU ownership and subdivision. As an example of "missing middle" housing, the 28th Avenue ADU Cluster aligns with the City of Seattle's recent Comprehensive Plan updates and Neighborhood Residential zoning reforms, which encourage gentle density increases in established neighborhoods. The result is a compact, ownership-oriented community that expands housing choice while fitting comfortably within the existing urban fabric of Mount Baker.