Accessory Structures in Bellingham, WA (2026)
7 verified accessory structures rules for Bellingham, Washington, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Bellingham allows up to two accessory dwelling units per lot, capping each ADU at 1,000 square feet and detached units at 24 feet tall under Bellingham Municipal Code § 20.10.036.
Bellingham ADU Zoning Standards
Some RestrictionsBellingham Municipal Code § 20.10.036(B)
5. a. No more than two ADUs shall be permitted in conjunction with the principal unit on a single lot of record. The ADUs may be in any configuration of attached or detached units. 6. a. An ADU shall not exceed 1,000 square feet. 7. b. A five-foot side and rear yard setback shall be provided... 8. A D-ADU shall be no higher than 24 feet under BMC 20.08.020, height definition No. 1 or 12 feet un...
ADU Impact Fees
Bellingham waives its multimodal transportation impact fee for ADUs built inside an existing single-family home or accessory building, if the space predates May 21, 2018.
Bellingham ADU Impact Fee Exemption
Light RestrictionsBellingham Municipal Code § 19.06.030(B)(1)
The creation of an accessory dwelling unit within an existing single-family structure or detached accessory building that was designed and built for human habitation under valid city building permits shall be exempt from the payment of multimodal transportation impact fees; provided, that: (a) the area being converted to an ADU was constructed as of May 21, 2018, and (b) the scope of the work d...
ADU Owner Occupancy
Bellingham does not require owner-occupancy to build or rent an ADU -- state law (HB 1337) bars that -- but an owner-occupied attached ADU is exempt from the rental registration fee under BMC 6.15.040(B)(4).
Bellingham ADU Owner-Occupancy Fee Rule
Few RestrictionsBellingham Municipal Code § 6.15.040(B)(4)
Accessory dwelling units when an owner resides in either the single-family residence or the ADU and the ADU is attached to the single-family residence. C. A residential rental registration expires on December 31st of the calendar year following registration or renewal. D. The residential rental registration is transferable to any person who has acquired ownership of a registered rental proper...
ADU Rental Restrictions
Bellingham allows short-term rentals in attached ADUs citywide but bars them in detached ADUs on residential-single lots, permitting detached-ADU rentals only in commercial, multi-family and urban village areas.
Bellingham ADU Short-Term Rental Limits
Significant RestrictionsBellingham Municipal Code § 20.10.037(B)(5)(a)-(c)
a. Short-term rentals are permitted in legally established attached accessory dwelling units citywide. b. Short-term rentals are permitted in legally established detached accessory dwelling units in commercial, residential multi and urban village general use type areas. c. Short-term rentals are not permitted in detached accessory dwelling units in residential single general use type areas.
Shed & Carport Rules
Bellingham caps detached accessory buildings like sheds and garages at 800 square feet and one story (12 feet), and lets them sit in rear yards or the rear 22 feet of a side yard.
Bellingham Accessory Building Size Limit
Some RestrictionsBellingham Municipal Code § 20.30.100
1. The regulations of BMC 20.30.040 shall apply to all accessory buildings except that: a. Accessory buildings shall not exceed one story in height, or 12 feet under either height definition. b. Accessory buildings may be located in a rear yard and in the rear 22 feet of an interior side yard... 4. An accessory building may not exceed 800 square feet in area, provided: a. The hearing examiner m...
Garage Conversions
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.
Bellingham Garage-to-ADU Conversion Rule
Some RestrictionsBellingham Municipal Code § 20.10.036(B)(15)
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.
Tiny Homes
Bellingham's building code locally adopts IRC Appendix Q, the tiny-house construction standard, giving builders a legal path to permit compliant tiny homes as accessory structures.
Bellingham Adopts IRC Tiny House Code
Some RestrictionsBellingham Municipal Code § 17.10.020 (Construction Administrative Code § 118, item 2)
SECTION 118: INTERNATIONAL RESIDENTIAL CODE TECHNICAL AMENDMENTS. The 2021 Edition of the International Residential Code, as adopted by BMC 17.10.010 is amended as follows: 1. Appendix F "Radon control methods" is adopted. 2. Appendix Q "Tiny houses" is adopted. 3. Appendix U "Dwelling unit fire sprinkler system" is adopted.
Looking for Whatcom County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Bellingham city rules.
Accessory Structures in Whatcom County →