Mercer Island is one of the most architecturally significant residential communities in the Pacific Northwest. Situated entirely on an island in Lake Washington, it offers unmatched waterfront access, proximity to Seattle and Bellevue, and a residential character that ranges from 1950s mid-century estates to contemporary waterfront compounds. Piper Cole Architects brings 25+ years of Seattle-area experience to Mercer Island projects.
Architecture Services on Mercer Island
- Waterfront Custom Homes — Maximizing lake views, dock access, and shoreline setback requirements
- Estate Renovation — Updating older Mercer Island homes while preserving their character and views
- ADU Design — Backyard cottages and attached ADUs under City of Mercer Island codes
- Home Additions — Expanding existing homes without compromising the site’s natural assets
Mercer Island Building Codes and Permit Process
Mercer Island projects are permitted through the City of Mercer Island Development Services. Shoreline properties are subject to additional Shoreline Master Program review. Mercer Island has specific tree retention requirements and critical area protections that affect buildable area on many lots. Piper Cole Architects navigates these requirements with experience gained from numerous Island projects.
Mercer Island ADU Rules
Mercer Island allows both attached and detached ADUs consistent with Washington State law. DADUs are permitted in residential zones with standard setback and height requirements. The Island’s premium rental market makes ADUs particularly attractive investments.