Bellingham, WA Accessory Structures: Garage Conversions (2026)
Garage conversion rules in Bellingham, WA, sometimes called garage-to-ADU or accessory living unit conversions, govern permits, ceiling height, egress, and parking replacement.
Key Facts
- Governing section
- BMC 20.10.036(B)(15)
- Setback/coverage relief
- Existing violations excused for conversion
- Max ADU size
- 1,000 sq ft (B)(6)(a)
- Max ADUs per lot
- Two, any configuration (B)(5)(a)
- Health/safety compliance
- Must meet BMC Titles 15 & 17 (B)(13)
- Excluded area
- Lake Whatcom Reservoir land, Ch. 16.80 BMC
Summary
Bellingham lets homeowners convert an existing detached garage into an accessory dwelling unit even if the garage itself violates today's setback or lot-coverage standards, under BMC 20.10.036(B)(15). The converted unit still needs an ADU permit, a building permit, and full compliance with the city's health and life-safety codes.
15. Conversion of Existing Accessory Structures to ADUs. ADUs may be converted from existing structures, including but not limited to detached garages, even if they violate current code requirements for setbacks or lot coverage.
Official source re-checked September 8, 2026: no newer edition of the code had been published (publisher’s edition: current through Ordinance 2026-06-015, passed June 1, 2026).
Full Breakdown
036(B)(15) allows conversion of existing accessory structures, including but not limited to detached garages, into ADUs "even if they violate current code requirements for setbacks or lot coverage" - meaning a garage sitting closer to the property line than a new structure could be built today does not have to be torn down or relocated to become a legal dwelling unit. That relief is narrow: it excuses the existing structure's nonconforming setback or lot coverage, but subsection (B)(13) still requires the converted unit to "comply with all standards for health and life safety as set forth in BMC Titles 15 and 17," the city's plumbing, mechanical and building codes, plus any other applicable regulations.
A converted garage-ADU is also capped at 1,000 square feet under (B)(6)(a), and any ancillary garage/workshop space attached to it is capped at 800 additional square feet under (B)(6)(b). The property still cannot exceed two ADUs total per lot (B)(5)(a). 80 BMC (Lake Whatcom Reservoir Regulatory Provisions) are excluded from ADU eligibility entirely under (B)(1). Owners of a garage or other accessory structure that was already functioning as an illegal dwelling before January 1, 1995 can apply to legalize it under subsection (C), using current building codes at the time they bring the unit forward for permit, though the city is not required to permit a unit the building official determines to be dangerous (C)(3). 10 BMC (subsection D).
Violations & Fines
Converting a garage without an ADU permit and building permit is a zoning code violation subject to the penalty and enforcement provisions of Chapter 20.52 BMC, which can include civil penalties and a compliance order from the planning and community development department. A conversion that fails the health and life-safety standards of BMC Titles 15 and 17 can be red-tagged by the building official under those titles' construction codes until brought into compliance.
Frequently Asked Questions
Can I convert my detached garage into an ADU if it's too close to my property line?
Does a converted garage still need a building permit?
Is there a size limit on a converted garage ADU in Bellingham?
What if my garage was already used as an illegal apartment before 1995?
Sources & Official References
Other rules in Bellingham
Compare Bellingham to another location·View the Washington accessory structures overview
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