Bainbridge Island permit guide
Building an ADU on Bainbridge Island: what the permit rules say
Quoted from Bainbridge Island's own pages, with the date we read them: October 13, 2026.
Short answer
Permit required
The City of Bainbridge Island's pre-approved ADU flyer says "The owner or applicant must apply for an ADU building permit with the City of Bainbridge Island Planning & Community Development (PCD)." The plans are free to use, but the City says "additional fees will be required as part of the permitting process." The flyer sets a 1,000 square foot size limit, a parking standard, and sewer, water and septic requirements. Source [1]Source [2]
The rule, quoted
From the City's pre-approved ADU flyer:
The owner or applicant must apply for an ADU building permit with the City of Bainbridge Island Planning & Community Development (PCD).
Maximum size of 1,000 square feet or less. If the accessory dwelling unit will be located within a building existing as of the approval date of Ordinance No. 2015-26 (for example, in a basement) the city may allow an increased size in order to efficiently use all floor area. If an accessory dwelling unit is constructed in conjunction with a garage, the square footage of the garage shall not count towards the 1000-square-foot limitation.
One off-street parking space is required for the ADU unless it is located within 0.25 miles of a transit stop or sufficient on-street parking exists.
Must connect to public sewer and water where available. If using a septic system, approval from the Kitsap Public Health District is required.
ADUs cannot be used for short-term rentals (e.g., Airbnb) unless an approved business license is obtained for that use.
What to submit
- To get the full stamped plan set, the City's ADU page says to complete the plan request form and email it to permittingsubmittal@bainbridgewa.gov. Source [2]
- The Permitting page says a complete application "will include" the Assessor's Tax Parcel Number, owner information (name, address, phone number and email address), the project site address, contractor information (including the contractor license number), and submittals "including Site Plan, Plan Sets, and other required information." Source [3]
- Applications go through the Public Permit Portal. Source [1]
Worth knowing
- "Pre-approved ADU plans are still required to undergo the necessary review process for project approval." Source [2]
- "All ADU plans will need to be reviewed by COBI staff in addition to the Building Department to ensure compliance with the City’s land use regulations, development standards, and environmental protection laws." Source [1]
- The City "strongly encourages anyone who is interested in building an ADU to contact the Planning and Community Development (PCD) Department to discuss site feasibility such as zoning, critical areas review, shoreline designations, and other land use requirements." Source [2]
- The flyer also lists how many ADUs are allowed per parcel. Because the City adopted interim development regulations on August 25, 2026, confirm the current count and size rules with PCD before you design. Source [4]
- The City's ADU definition is in Bainbridge Island Municipal Code (BIMC) 18.36.030.10. Source [2]
Sources
Where this comes from
Compiled from Bainbridge Island's published rules; last checked
JKM pulls the permit as part of the job
Call Ian Laughlin at (206) 226-1988, or send the address and the scope. We find the right office and take it from there.