Seattle does not require a construction permit for a detached, one-story storage or growing shed with a roof footprint of 120 square feet or less, a simple foundation, no occupancy, and no environmentally critical-area conflict; otherwise a permit is required.
Land-use setbacks, height, lot coverage, utilities, shoreline, flood, landmark, and environmentally critical-area rules remain separate.
What this tells youComputed rule answer
How precise this isComputed rule answer
Official data checkedSeattle sheds guidance
Next stepCheck the official shed/accessory-structure rules with your project dimensions.
No construction permitAll exemption conditions must be met: detached, one story, roof footprint 120 sq ft or less, simple foundation, unoccupied storage/growing use, no ECA conflict
Permit requiredAny exemption condition is not met
Still verifyLand-use setbacks, height, lot coverage, utilities, shoreline, flood, and landmark rules