When is a building permit required? The International Building Code exempts certain structures from needing a building permit if they are less than 200 square feet and unconditioned space. Exempted structures do not require a building permit from the County but must comply with all King County code requirements.
Storage sheds that are less than 120 square feet and eight feet in height do not require a building permit, but still require Planning Division approval through an over-the-counter application called a Zoning Clearance.
Please note, Sheds and/or Structures under 120 square feet do require a Planning Permit.
The biggest sized shed you can build in Washington state without a permit is one with a roof square footage of 120 square feet, no taller than one story.
Storage sheds less than 120 square feet in area do not require a building permit.
Building codes are laws that set minimum requirements for how structural systems, plumbing, heating, ventilation and air conditioning (HVAC), natural gas systems and other aspects of residential and commercial buildings should be designed and constructed.