Seattle Accessory Structure Permit Guide: Sheds, Garages, Studios, and More

Not every backyard structure requires a building permit in Seattle — but many do. Here is a guide to when permits are required for accessory structures.

Exempt Structures (No Permit Required)

• Detached accessory structures under 200 sq ft floor area AND not exceeding 15 feet in height AND not used for human habitation AND not located in a flood zone or critical area
• Simple patios, walkways, driveways at grade
• Fences under 8 feet tall (except in shoreline areas)

Permit Required

• Any structure over 200 sq ft
• Any structure exceeding 15 feet in height
• Garages (attached or detached), regardless of size
• Carports over 200 sq ft
• Any structure used for habitation (ADU, studio, office)
• Structures in flood zones or critical areas

Setback Requirements for Accessory Structures

In most Seattle residential zones, accessory structures must be:

• 5 feet from rear lot line
• 5 feet from side lot lines
• Behind the primary structure or at least 20 feet from front lot line

When a Permit Is Required: What It Involves

Permitted accessory structures require a site plan, floor plan, elevation drawings, and energy compliance documentation if heated. Structural drawings are required for any structure with a concrete foundation or more than basic wood framing.

Piper Cole Architects designs and permits accessory structures of all types. Free consultation — call 425-753-6452.