Zoning, building permits and land rules in San Anselmo, California

At a glance

Building permit

Issued by the Town of San Anselmo Building Department for construction and demolition inside the town²

Zoning

Town zoning applies inside San Anselmo; the county's zoning does not¹⁵

Building code

2025 California codes adopted by reference, with town amendments⁶

Septic

Marin County Environmental Health Services administers septic permits countywide³

RV living

Occupying a trailer or RV for living or sleeping is unlawful on any lot, with narrow exceptions⁴

Lot coverage (R-1 flatland)

Table 4F sets a lot coverage ratio of 0.35 of lot size⁷

Owner-builder

California's owner-builder licensing exemption has conditions; the town still issues the permit⁸

Who to call

Contact details are copied from each office’s official page and were checked against it on October 16, 2026.

Do you need a building permit in San Anselmo, California?

Construction and demolition inside the Town of San Anselmo go through the town's own Building Department, which reviews plans and issues building permits². The town has adopted the 2025 California construction codes by reference, including the residential code and its Appendix Q for tiny houses, with local amendments⁶. The county's building-permit rules apply only to unincorporated Marin County⁹, so the county's exemptions for small sheds do not carry into town. We could not confirm the town's own exemption list, inspection steps or fee schedule; ask the Building Department before you assume any project is exempt².

Who handles building permits and planning in San Anselmo?

Building permits come from the town's Building Department and zoning questions go to the Planning Department, both at Town Hall on San Anselmo Avenue²¹⁰. Planning also publishes a parcel lookup for finding your zoning district¹⁰. Incorporated Marin towns make their own planning and zoning laws, while the county covers only unincorporated land⁵. Do not call the county planning counter about a San Anselmo address.

Does San Anselmo have zoning, and what does it mean for lot size and setbacks?

San Anselmo has its own zoning ordinance, which includes an R-1 single-family district¹. Dimensional rules differ by district. In R-1 lots below 150 feet mean sea level, Table 4F sets a maximum lot coverage ratio of 0.35 of lot size and also caps floor area, and lots above 150 feet use a separate table⁷. We could not confirm minimum lot sizes, setbacks or height limits for the town's districts; look up your parcel's district with the Planning Department¹⁰.

How do septic permits work inside San Anselmo?

Septic permits in Marin County come from the county's Environmental Health Services³, and new, replacement and repair work needs a septic permit¹¹. Whether a given San Anselmo lot is on public sewer or septic, and which sanitary district serves it, we could not confirm. Where a parcel is near a public sewer main, county rules can require connection instead of septic expansion¹². Call Environmental Health Services at the number below before you plan an onsite system¹³. Countywide, only a small share of soils rate well for conventional drain fields, so expect a site evaluation¹⁴.

Can you live in an RV or tiny home in San Anselmo?

No for RVs on a lot: San Anselmo's code makes it unlawful to camp in or occupy a trailer, camper or recreational vehicle for living or sleeping on any lot, private street or public place, except under two specified code sections⁴. Parking or storing an RV on your own property is allowed if a solid fence screens it and it does not block sightlines or become a nuisance⁴. Sleeping in a non-trailer vehicle in the backyard of developed property is allowed with the occupant's permission¹⁵. For tiny homes, the town adopts the residential code's tiny-house appendix⁶, but we could not confirm where a tiny home may be occupied; ask the Planning Department¹⁰.

Building a home in San Anselmo: the steps, in order

1. Look up your parcel's zoning district with the Planning Department¹⁰.
2. Confirm sewer or septic service; septic goes through county Environmental Health Services³.
3. Check whether the parcel is in a special flood hazard area, where the town sets elevation rules for development¹⁶.
4. Apply for the building permit with the Building Department².
5. If you plan to build it yourself, note that California's owner-builder exemption is a contractor-licensing exemption with conditions, such as not offering the work for sale⁸.

What to check before you buy land in San Anselmo

Flood zones matter: in the town's special flood hazard areas, manufactured homes must sit with the lowest floor at least 3 feet above base flood elevation outside existing parks¹⁶. Marin County's typical home value is about $1,504,466¹⁷, and the effective property tax rate is 0.7%¹⁸. Land outside town limits follows the county's rules, which differ; see the Marin County page for unincorporated land.

Watch-outs

• San Anselmo's building permit exemptions, fees, setbacks and minimum lot sizes are not confirmed here; call the Planning Department or Building Department before you buy¹⁰.
• The county's shelter-crisis RV and tiny-home provisions apply only in unincorporated Marin County, not inside San Anselmo¹⁹.
• Searching "Marin County permits" returns the county's unincorporated-area rules; inside San Anselmo, the town's offices issue permits⁵.

Sources

1. San Anselmo Code 10-3.412 Maximum Floor Area and Lot Coverage, Single-Family Below 150 MSL (Town of San Anselmo), quoted and re-checked
2. Town of San Anselmo Building & Safety (Development Services) (sananselmo.gov)
3. Septic systems/onsite wastewater treatment systems, quoted and re-checked
4. San Anselmo Code 5-5.02 Trailers prohibited for living or sleeping purposes: Camping prohibited (Town of San Anselmo), quoted and re-checked
5. Title 22 - Development Code, quoted and re-checked
6. San Anselmo Code 9-1.101 Adoption of Construction Codes (Town of San Anselmo), quoted and re-checked
7. San Anselmo Code 10-3.412 Maximum Floor Area and Lot Coverage, Single-Family Below 150 MSL (Town of San Anselmo), quoted and re-checked
8. Owner-Builder Overview, quoted and re-checked
9. Do I need a building permit?, quoted and re-checked
10. Town of San Anselmo Planning Department (sananselmo.gov)
11. Septic systems/onsite wastewater treatment systems, quoted and re-checked
12. Regulations for Design, Construction and Installation of Individual Sewage Disposal Systems, quoted and re-checked
13. Marin County Community Development Agency - Environmental Health Services (marincounty.gov)
14. 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
15. San Anselmo Code 5-5.02 Trailers prohibited for living or sleeping purposes: Camping prohibited (Town of San Anselmo), quoted and re-checked
16. San Anselmo Code 7-11.504 Standards for manufactured homes (flood hazard) (Town of San Anselmo), quoted and re-checked
17. Typical home value (Zillow): Bolthole Index county data
18. Effective property tax rate: Bolthole Index county data
19. County Declares Shelter Crisis to Provide Temporary Emergency Housing, quoted and re-checked

Written October 16, 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.