How tall can a detached Bellingham ADU be?
✓ Verified against code · August 20, 2026
Either 24 ft or 12 ft, depending on which of the city's two height definitions you measure by. The first measures from the lowest existing grade at the wall and allows 24 ft; the second measures from the highest existing grade within 20 ft of the building and allows 12 ft. Where both are genuinely available to your site, you elect which to use, subject to the director agreeing the choice won't be unduly detrimental to neighbouring properties. On a sloping lot that election is the single most consequential decision in the design.
Citation: BMC 20.10.036(B)(6)(c); BMC 20.10.070
How current is this?
Bellingham’s ADU rules run under BMC 20.10.036 (Accessory Dwelling Units) (Ordinance 2025-12-035 §2). Bellingham completed its HB 1337 alignment in Ordinance 2025-12-035, effective December 23, 2025 — roughly six months after the state's June 30 deadline. Two of the standards below rest on interim ordinances rather than permanent code: the citywide elimination of parking minimums, and the companion infill regulations that sunset in December 2026. We verified this answer against primary sources on August 20, 2026, and every change we catch is logged in the changelog.
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Not legal advice — lot-specific overlays can change the answer for your parcel. The citation above points at the governing code section; check it, or ask the city to confirm.