The City of Williams, in Colusa County, California, adopts its own zoning in Title 17 of its municipal code1. The city's Building Department administers and enforces the building codes inside city limits2. We could not confirm who issues septic permits inside Williams, so ask Colusa County Environmental Health3. Land outside city limits follows the county's rules instead4.
At a glance
- Zoning
- Williams adopts its own zoning (Title 17) inside city limits1
- Building permits
- City Building Department, with online applications2
- Planning
- City Planning & Zoning Department5
- Septic
- Not confirmed for city addresses; ask Colusa County Environmental Health3
- RV living
- Street parking limited; private-lot rule not confirmed6
- Manufactured homes
- Allowed where single-family houses are allowed7
- Accessory dwellings
- Allowed under state law and the city code8
- Owner-builder
- State licensing exemption exists; it is not a permit exemption9
Who to call
Building permits
City of Williams Building Department
Building permits and inspections inside Williams city limits
810 E Street, Williams, CA 95987
Building permits
City of Williams Building Department (permit page)
Code administration, online permit application and inspection scheduling
Planning & zoning
City of Williams Planning & Zoning Department
Zoning questions and city planning approvals inside Williams city limits
460 8th Street, Williams, CA 95987
Septic permits
Colusa County Environmental Health
County septic and water-well permits; ask whether they cover a Williams city address
1213 Market Street, Colusa, CA 95932
Contact details are copied from each office’s official page and were checked against it on October 16, 2026.
Off-grid gear
Going off-grid in Williams means bringing your own water and power. The kit we’d start with:
- Water Crystal Quest Filter any source — well, rain, or creek — to drinking-clean.
- Power Bluetti Solar generators and home battery backup for living off the grid.
- Septic Soil percolation test kit Run your own perc test before paying an engineer — the first thing a septic office asks about.
- Water Well water test kit Bacteria, nitrates, hardness — know what the well on a parcel is really pumping.
These are affiliate links — we may earn a commission, at no cost to you. As an Amazon Associate, Bolthole Index earns from qualifying purchases.
Does Williams, CA have zoning, and what does it mean for lots and setbacks?
Yes. The City of Williams zones land inside city limits through Title 17 of its municipal code, which lists permitted, limited, conditional and prohibited uses district by district1. The county's zoning code does not reach incorporated cities, so Williams addresses answer to the city, not the county4.
Dimensional rules differ by district. We could not confirm the lot-size, height or main-building setback standards for Williams' residential districts, so ask the Planning & Zoning Department5 before you buy.
One setback we did confirm: an accessory dwelling unit that is not converted from an existing structure needs a 4-foot side and rear setback10. Manufactured homes are allowed wherever single-family houses are allowed, under the same development standards7.
Do you need a building permit in Williams, and who issues it?
The City of Williams Building Department is responsible for administering and enforcing the building codes inside city limits11. Inside Williams, building permits come from that office, not from the Colusa County Building Department, which serves unincorporated land12.
We did not confirm the city's list of permit-required work, its fees, or its owner-builder rules, so call the Building Department at the number below before you start. Applications go through the city's online permit portal, and field inspections are scheduled on Mondays11.
California's owner-builder exemption covers contractor licensing only; it does not by itself waive building permits or inspections9. The 2025 California Building Standards Code applies to permit applications dated on or after January 1, 202613.
How do septic permits work inside Williams?
We could not confirm who issues septic permits for Williams addresses, or whether a given city lot is on sewer or septic. Start with Colusa County Environmental Health, which runs the county's septic and well program3, and ask the city's Building Department whether your lot has sewer service.
Statewide, every new or replacement septic system needs a permit from the local city or county agency or from the regional water board14. In unincorporated Colusa County the Environmental Health Division issues those permits, and a site evaluation comes before approval15. Colusa County's soils are a reason to plan ahead: only about 3.9% of soils are rated not limited for a conventional drain field, so expect a site evaluation and possibly an engineered system16.
Can you live in an RV or tiny home in Williams?
The part of the Williams city code we reviewed covers RVs on public streets, not private lots. A recreational vehicle may park on a city street for a limited time while its owner conducts lawful business, and a guest of an adjacent resident may stay at most 72 continuous hours, or longer with written approval of the chief of police6. That is a parking rule, not permission to live in an RV.
We could not confirm a Williams rule for RV or tiny-home living on a private lot. Unless a local ordinance says otherwise, California generally limits RV occupancy to mobilehome parks and special occupancy parks17. A tiny home must qualify as a recognized type of structure, such as a manufactured home or a code-built home, to be legally occupied18.
Accessory dwelling units are allowed inside Williams under state law and the city code8.
How do you build a home in Williams? The steps, in order
- Confirm the lot is inside city limits and ask the Planning & Zoning Department which district it is in and what that allows15.
- Ask Colusa County Environmental Health, and the city, whether the lot is on sewer or needs a septic system and well3.
- Apply for the building permit through the city's online portal and pass the Monday field inspections11.
- If you want a second unit, check the accessory dwelling rules and the 4-foot side and rear setback810.
- If you act as your own builder, file the owner-builder declaration your permit office requires and remember it only covers contractor licensing9.
What stays with Colusa County, and what to check before you buy near Williams?
City zoning and city building permits apply only inside Williams. For unincorporated land, see the Colusa County page: the county zoning code covers unincorporated land only4, and temporary RV occupancy during construction there requires a Temporary Use Permit19.
A driveway onto a state highway needs a Caltrans encroachment permit20. Water-well permits come from the local environmental health agency21. Colusa County's effective property tax rate is 0.7%22, and the median bill is $2,481 a year23.
Watch-outs
- We could not confirm Williams' residential lot-size, height or main-building setback rules; ask the city Planning & Zoning Department5.
- We could not confirm who issues septic permits or wells inside Williams; ask Colusa County Environmental Health3.
- A street-parking rule for RVs is not permission to live in one; private-lot RV living inside Williams is unconfirmed6.
Sources
- Williams Code 17.01.030 Permitted; limited; conditional; and temporary uses (Williams), quoted and re-checked
- City of Williams Building Department (cityofwilliams.org)
- Colusa County Environmental Health (countyofcolusaca.gov)
- Colusa County Zoning Code, quoted and re-checked
- City of Williams Planning & Zoning Department (cityofwilliams.org)
- Williams Code 10.32.340 Recreational vehicles (Williams), quoted and re-checked
- Williams Code 17.01.030 Permitted; limited; conditional; and temporary uses (Williams), quoted and re-checked
- Williams Code 17.01.030 Permitted; limited; conditional; and temporary uses (Williams), quoted and re-checked
- California Business and Professions Code Section 7044 (California statewide rule), quoted and re-checked
- Williams Code 17.01.050 Supplemental residential standards (Williams), quoted and re-checked
- City of Williams Building Department (permit page) (cityofwilliams.org)
- Building Permits, quoted and re-checked
- Approved Building Standards (California statewide rule), quoted and re-checked
- 2023 OWTS Policy (California statewide rule), quoted and re-checked
- Colusa County Onsite Wastewater Treatment Systems Ordinance, quoted and re-checked
- 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
- hcd.ca.gov (California statewide rule), quoted and re-checked
- Information Bulletin 2016-01: Tiny Homes (California statewide rule), quoted and re-checked
- countyofcolusaca.gov, quoted and re-checked
- Encroachment Permits | Caltrans (California statewide rule), quoted and re-checked
- Well Standards (California statewide rule), quoted and re-checked
- Effective property tax rate: Bolthole Index county data
- Median property tax bill: Bolthole Index county data
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.