Accessory Structure

This application is for construction of a structures that are accessory to a primary residential use only like, sheds, fences, retaining walls, decks, rockeries, etc. Building systems (mechanical, electrical and plumbing) are separate permits. Detached Accessory Dwelling Units (ADU) should use the New Residential Building Permit application.

The following materials are the minimum that must be submitted to review your application: 

1. Proof of connection to public sewer or letter from King County Environmental Health reflecting adequate septic drain field and reserve space for change of use
2. Written narrative, include:
3. Description of the property
   • Scope of the project: 
   • Is the ADU attached or detached?
   • Is an existing structur or space being converted, i.e. a garage, or basement?
   • Square footage of the ADU
4. Site Plan, include:
   • Location, dimensions, and use of existing structures on site (include fences, accessory buildings, temporary structures such as trailers/mobile homes, and retaining walls)
   • Location and dimensions of proposed accessory dwelling unit
   • Distances between proposed structures, existing structures, and property lines
   • Indicate all structures to be removed / demolished
   • Location of existing private and public utility lines and/or easements
   • On-site vehicular access such as driveways, private roads, and parking areas
   • Location, dimension, and number of parking spaces
5. Conceptual Architectural Plan, include:
   • Building facades drawn at 1/4", 1/8" = 1' or comparable scale showing:
     • Elevations
     • Building height
     • Entrances
   • Floor plans with uses labeled