Building permits, zoning and septic rules in Bellingham, Washington

At a glance

Zoning

Yes: city zoning under BMC Title 20 inside city limits¹

Building permits

Applied for through the City of Bellingham Permit Center²

Building code

Washington State Building Code, enforced by cities and counties⁵

Septic

Whatcom County Health and Community Services issues septic permits countywide³

Lake Whatcom watershed

Septic systems prohibited; ADUs not allowed⁴⁶

Accessory dwellings

Allowed outside the Lake Whatcom watershed, up to 2 per lot⁶

Owner-builder

Owners working on their own property are exempt from contractor registration; permits still apply⁷

Minimum home size

State building code sets interior-space requirements⁸

Who to call

Contact details are copied from each office’s official page and were checked against it on October 14, 2026.

Does Bellingham have zoning, and what does it mean for ADUs, setbacks and height?

Bellingham has its own zoning: the city's development standards are in BMC Title 20, and BMC 16.80.080 modifies them in the Lake Whatcom watershed¹. Zoning inside city limits is the city's job, not Whatcom County's.

For accessory dwelling units, the city's ADU Quick Guide says ADUs are allowed in all areas that allow residential development, except the Lake Whatcom watershed⁶. Bellingham allows up to 2 ADUs per lot, each up to 1,000 square feet⁶. ADU setbacks are at least 10 feet at the front and 5 feet on an interior side⁹. A detached ADU can be up to 24 feet tall under the city's first height definition¹⁰.

We could not confirm the district-by-district lot sizes, setbacks and coverage for principal homes; the Permit Center can tell you what applies to a specific parcel².

Do you need a building permit in Bellingham, and who issues it?

Building projects inside Bellingham are applied for through the City of Bellingham Permit Center, not the Whatcom County permit counter². Washington's state building code applies in all cities and counties, and cities and counties enforce it⁵.

For an ADU, the city requires both a land use permit and a building permit, and the land use permit must be approved before the building permit is issued¹¹. Most ADUs go through a Type I process, though other processes apply in some cases¹².

We could not confirm the city's general permit exemptions or its fee schedule. Call the Permit Center before assuming a project is exempt².

How do septic permits work in Bellingham?

Whatcom County Health and Community Services runs the on-site sewage program and requires a septic permit to construct, repair, replace, modify, connect to or expand a septic system³¹³. We could not confirm who handles septic or sewer connection for a specific address inside the city, so ask the county Health office whether your lot is sewered¹⁴.

In the Lake Whatcom watershed part of Bellingham, the city's code says septic systems are prohibited⁴. Elsewhere in the county, conventional drain fields rate poorly on soils: only about 0.5% of Whatcom County soils rate as not limited, so expect a site evaluation or an engineered system on unsewered land¹⁵.

Can you live in an RV or tiny home in Bellingham?

We could not confirm Bellingham's rules on RV occupancy, temporary camping or tiny homes; the city's own code, BMC Title 20, is where they would be set, and the Permit Center is the office to ask¹². Whatcom County's rules for RVs during construction apply to unincorporated land only and do not carry into the city¹⁶.

Building a home in Bellingham: the steps, in order

1. Confirm the zoning district and whether the lot is in the Lake Whatcom watershed with the Permit Center¹².
2. Ask Whatcom County Health whether the lot will use public sewer or needs a septic permit³.
3. For an ADU, get the land use permit approved first¹¹.
4. Apply for the building permit through the Permit Center².
5. If you are building on your own property, owner-builder status exempts you from contractor registration but not from permits⁷.

What stays with Whatcom County, and what to check before you buy

Septic permits come from Whatcom County Health and Community Services, not the city³. Whatcom County's own building and zoning rules apply to unincorporated land, not to lots inside Bellingham¹⁷; see the Whatcom County page for land outside city limits.

Whatcom County's effective property tax rate is 0.7%, with a median bill of $3,819 a year¹⁸¹⁹. Floodplain, driveway and other rules for a specific lot were not confirmed for the city, so ask the Permit Center before you close².

Watch-outs

• Lots in the Lake Whatcom watershed face extra limits: septic systems are prohibited and ADUs are not allowed⁴⁶.
• Whatcom County's rules apply to unincorporated land only; inside Bellingham, check BMC Title 20 and call the Permit Center¹².
• We could not confirm Bellingham's permit fees, building-permit exemptions or RV and tiny-home rules; ask the Permit Center².

Sources

1. City of Bellingham Municipal Code excerpts 16.80.080 and 20.16.020 (Bellingham), quoted and re-checked
2. City of Bellingham Permit Center (cob.org)
3. Onsite Sewage, quoted and re-checked
4. City of Bellingham Municipal Code excerpts 16.80.080 and 20.16.020 (Bellingham), quoted and re-checked
5. RCW 19.27.031 — State building code—Adoption—Conflicts—Opinions (Washington statewide rule), quoted and re-checked
6. City of Bellingham ADU Quick Guide (Bellingham), quoted and re-checked
7. Washington State Legislature - RCW 18.27.090 Exemptions (2026 county census)
8. WAC 51-50-1208 — Section 1208—Interior space dimensions (Washington statewide rule), quoted and re-checked
9. City of Bellingham ADU Quick Guide (Bellingham), quoted and re-checked
10. City of Bellingham ADU Quick Guide (Bellingham), quoted and re-checked
11. City of Bellingham ADU Quick Guide (Bellingham), quoted and re-checked
12. City of Bellingham ADU Quick Guide (Bellingham), quoted and re-checked
13. Onsite Sewage, quoted and re-checked
14. Whatcom County Health and Community Services - On-Site Sewage System (OSS) Program (whatcomcounty.us)
15. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
16. Chapter 20.20: Urban Residential (UR) District, quoted and re-checked
17. Development Regulations, quoted and re-checked
18. Effective property tax rate: Bolthole Index county data
19. Median property tax bill: Bolthole Index county data

Written October 14, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.