Bellingham changed its ADU rules in 2025, and most homeowners still do not know it. Under the city's ordinance update (BMC 20.10.036), most single-family lots can now have up to two ADUs, a detached unit can reach 1,000 square feet and 24 feet tall, the owner-occupancy requirement sunsets July 1, 2026, and off-street parking requirements are waived in the current window. That is a real shift, and it is exactly the kind of thing worth walking through before you spend anything.
We build all over town, from the older homes up on the hills around Sehome and South Hill to the newer flats out toward Barkley and Cordata. The work changes with the neighborhood. The 1910s and 1920s stock near downtown often means basement conversions and garage conversions with old slabs and undersized panels, while the newer east-side subdivisions are better suited to ground-up detached cottages. Whatever your lot is, we start with a free feasibility check against your zoning and setbacks, then design, permit, and build a unit that passes inspection and lasts through our wet winters.
ADU costs in Bellingham depend on the type. A ground-up detached backyard cottage runs $250,000 to $400,000 or more, a garage conversion runs $80,000 to $150,000, and a basement apartment conversion runs $90,000 to $180,000. The drivers are size, finish level, site access, and how far we run utilities to the unit. We give you a line-item number after a free site visit, so you know exactly what your project costs before you commit.
Do you build ADUs in Bellingham?
Yes. Bellingham is one of our core service areas, and we build backyard cottages, garage conversions, in-law suites, and basement apartments here. We start every project with a free feasibility check against your lot size, setbacks, and the City of Bellingham rules, so you know what your lot allows before you spend anything on design.
Who handles the permit for an ADU in Bellingham?
We do, start to finish. Inside city limits, your ADU runs through the City of Bellingham, with its setbacks, stormwater rules, and connection fees. We pull and manage the permit for you. We assemble the full permit package, manage the review including answering reviewer comments, and carry it through to an approved permit, then handle the inspections during the build.
Ready for a free Bellingham feasibility check?
Tell us about your lot and your goal. We'll reply within 15 minutes during business hours.