Building permits, zoning and land rules in San Juan County, Washington

San Juan County requires building permits for construction, alteration and repair in the unincorporated county through the Department of Community Development; the county building code applies within unincorporated San Juan County¹. The county Building Department administers the state-adopted building, residential, mechanical, plumbing, fuel-gas, energy, indoor-air-quality and ventilation codes¹⁰. Accessory structures typically defined as Group M1 or M2 may qualify for a statement of exemption when they are accessory to a private residence or used for agriculture and are not used for human habitation¹. The county’s published material does not provide a complete exemption list, so ask Community Development whether a particular shed, repair or other scope needs a permit¹¹. Sewage-disposal and water-availability applications go separately to Health & Community Services with the appropriate fee¹. Required life-safety inspections are requested through the Permit Center or the inspection hotline¹⁰. Every new-construction project requires a certificate of occupancy after all items pass final inspection; stand-alone mechanical or plumbing work and repairs do not¹². An owner-builder building permit costs 57.5% of the conventional fee, with a $69 minimum, and building permits and inspections still apply¹³.

The San Juan County Department of Community Development handles building permits and inspections, code enforcement, land-use designations and planning¹¹. The office is at 135 Rhone Street in Friday Harbor, and its phone number is 360-378-2354¹¹. File building-permit applications online through the SJC Permit Center after preparing recent water-availability and sewage records, a site plan and construction drawings². Plumbing and mechanical routing and termination plans are required for all permits beginning May 1, 2025². Published conventional building-permit fees are valuation-based with a $69 minimum, and conventional plan review is 65% of the building-permit fee¹³.

San Juan County has zoning, with most land-use standards and permit requirements in Title 16 and Title 18, the Unified Development Code⁴. The Unified Development Code regulates current and proposed land use, infrastructure and facilities³. Rules vary among county zoning districts and distinct subarea plans, including the listed planning areas for Eastsound, Lopez Village, Deer Harbor, Doe Bay/Westsound, Olga, Orcas Village, Shaw Island and Waldron Island⁴. Setbacks fall under Chapter 18.60 of the county code: outside activity centers and urban growth areas, road setbacks are measured from the centerline of the existing road rather than the right-of-way edge, and side and rear setbacks are measured from the property edge¹⁴. Building height and lot coverage are set by district, and approved subarea plans may set different heights in rural districts¹⁴. We could not confirm a single minimum lot size, so a parcel’s allowed use and dimensional standards require a parcel-specific check. Dividing land is regulated separately under the Unified Development Code¹⁵. Community Development handles land-use designations and planning, so confirm the designation and applicable standards before relying on a listing or a neighboring property¹¹.

San Juan County Health & Community Services administers on-site sewage systems where municipal treatment is unavailable and assists with siting, design, installation, operation and maintenance⁵. Submit sewage-disposal and water-availability applications directly to that department with the appropriate fee². After installation, gravity systems need inspection every three years unless they are in a designated sensitive area; pressure, sand-filter, mound, aerobic-treatment and sensitive-area gravity systems need annual inspection⁵. A licensed wastewater inspector or county-trained certified homeowner must perform the inspection⁵. Because 0% of mapped county soils are rated free of severe limitations for a conventional drain field, make site evaluation and system design early purchase contingencies¹⁶.

We could not confirm a San Juan County rule that generally allows RV occupancy on private land. The one county rule we found is narrow: a mobile home park may have an RV storage area for residents' RVs, with no utility hookups, and no RV in that storage area may be used as living quarters¹⁷. So ask Community Development about the parcel, duration and utility arrangement before moving an RV onto a site¹¹. Washington’s statutory RV definition in the manufactured-home context describes an RV as temporary, transient quarters that are not a primary residence, but that definition does not create general permission to live in one on private land¹⁸. A Washington tiny house may be built on wheels and may be no larger than 400 square feet, but it must meet the state building code and still needs local approval for its foundation, installation and location⁷. A new detached accessory dwelling outside urban growth areas and activity centers must first win an eligibility number through the county ADU lottery, and cannot be separately leased for less than 30 days¹⁹.

1. Ask Community Development to identify the parcel’s zoning district or subarea plan and the standards governing the home^4,11.
2. Start sewage-disposal and water-availability review with Health & Community Services².
3. Prepare recent water and sewage records, a site plan, construction drawings, and the required plumbing and mechanical routing plans².
4. Submit the building-permit application online through the SJC Permit Center².
5. If the property needs a new detached accessory dwelling, obtain an ADU eligibility number before applying¹⁹.
6. If acting as your own contractor, confirm that the contractor-registration exemption fits; it does not waive permits and excludes work for sale, demolition or lease⁶.
7. Complete required inspections and obtain the certificate of occupancy after all items pass final inspection¹².

Make septic feasibility a purchase contingency because 0% of mapped San Juan County soils are rated free of severe limitations for a conventional drain field¹⁶. Confirm legal water availability with Health & Community Services, since the county routes water-availability applications to that department alongside sewage paperwork^2,20. Review floodplain status and road access before choosing a homesite, because floodplain development needs a local permit and a new county-road approach needs county permission^9,21. The county averages 28.8 inches of precipitation annually, while 71.3% of its land is at a slope of 15% or less¹⁶. The effective property-tax rate is about 0.6%, and the median annual property-tax bill is about $4,131¹⁶.