Bolthole Index

Colusa County, California

Zoning, building permits and septic rules in Colusa, California

The City of Colusa administers its own zoning ordinance and runs its own building department, which issues permits, reviews plans and inspects work inside city limits12. The city's pages do not say which projects need a permit, so call the building department before you start. We could not confirm who issues septic permits inside the city; Colusa County Environmental Health handles them in unincorporated Colusa County3.

At a glance

Zoning
City of Colusa administers its own zoning ordinance inside city limits1
Building permits
Issued by the city building department; the city does not publish which projects need one45
Septic
Not confirmed inside city limits; county Environmental Health handles it in unincorporated areas3
Minimum lot (R-1)
8,000 square feet, 80 feet wide, 100 feet deep6
Front setback (R-1)
20 feet7
Height limit (R-1)
35 feet, two and one-half stories8
RV living
No citywide rule confirmed; flood-zone RVs limited to under 180 consecutive days9
Sewer
City water service requires connecting to city sewer first10

Who to call

Building permits

City of Colusa Planning and Building

Building permits, plan review, inspections and Certificates of Occupancy inside Colusa city limits; the Planning Division handles land use permits, subdivisions and environmental review ([email protected])

(530)458-4941

[email protected]

Septic permits

Colusa County Environmental Health

Onsite wastewater (septic) permits and water-well permits and inspections for Colusa County

(530) 458-0888

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 Colusa means bringing your own water and power. The kit we’d start with:

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Does Colusa, California have zoning, and what does it mean for lot size and setbacks?

Yes. The City of Colusa administers its own zoning ordinance for land inside city limits1. The published code covers R-1 and R-2 residential districts, mixed-use districts and a floodplain district, and the reviewed code does not reproduce the full list of districts11.

Rules differ by district, so find your parcel's district first. In R-1 Single Family Residence, the minimum lot is 8,000 square feet, 80 feet wide and 100 feet deep6. The front setback is 20 feet, and the rear setback is 20% of lot depth, never less than 15 feet and never more than 30 feet7. Main buildings may cover up to 35% of the lot12, and height is capped at two and one-half stories or 35 feet8.

In R-2 Two Family Residence, a single-family lot needs 6,000 square feet and a duplex lot needs 7,000 square feet13. Main buildings may cover up to 40% of the lot14. Dividing a lot is regulated by the city's subdivision chapter, with public hearings before the Planning Commission15.

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

The City of Colusa building department issues building permits, reviews plans, schedules and conducts inspections, and issues a Certificate of Occupancy for work inside city limits42. The city's page does not list which projects need a permit, and it publishes no application checklist or processing timeline, so ask the department before you buy materials or hire a crew5.

Contact the building department at [email protected] or (530)458-49412. The Planning Division handles land use permits and subdivisions at [email protected]2.

The Colusa County Building Department handles permits on unincorporated land, not inside the city. The county requires permits for any structure over 120 square feet there16. Do not assume the city uses the same threshold; we could not confirm one for city limits.

How do septic permits work inside Colusa?

We could not confirm whether the county's septic program applies inside the city of Colusa or whether city sewer rules replace it. Ask Colusa County Environmental Health at (530) 458-0888 before you plan any septic system on a city lot17.

Two facts narrow the question. Anyone taking city water must first connect to the city sewer system, and a meter application is also required10. In unincorporated Colusa County, new and replacement septic systems need an installation permit from Environmental Health after a site evaluation18. That county rule is not confirmed for lots inside Colusa city limits.

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

We found no citywide rule on living in an RV or tiny home in Colusa, so ask the building department and Planning Division before you park or place one. The one RV rule we confirmed applies to mapped flood-hazard zones A1-30, AH and AE: an RV there must stay fewer than 180 consecutive days and be licensed and ready for highway use, or meet the ordinance's permit, elevation and anchoring requirements for manufactured homes9.

Camping is prohibited at the city boat launch facility between 10th and 8th Streets along Main Street, but that rule is specific to that facility and is not a citywide camping rule19. Separately, no official city provision on tiny-home occupancy was located.

Building a home in Colusa: the steps, in order

  1. Find your parcel's zoning district and confirm lot size, setbacks and height with the city Planning Division112.
  2. Check the flood map: in an area of special flood hazard, a new home needs its lowest floor at least one foot above base flood elevation, certified by an engineer or surveyor20.
  3. Ask Colusa County Environmental Health whether sewer or a septic permit applies to your lot17.
  4. Submit your permit application to the city building department, which reviews plans and schedules inspections4.
  5. Request inspections as work proceeds, then ask for a Certificate of Occupancy21.

What stays with Colusa County, and what should you check before you buy?

The county's building, zoning and septic rules described on Colusa County's page apply to unincorporated land, not to parcels inside the city. Inside city limits, the city sets zoning and issues building permits14. Septic and well permits for county land come from Colusa County Environmental Health322.

Flood zone status matters: the city requires an elevation of at least one foot above base flood elevation for new residential construction in A zones20. Colusa County's effective property tax rate is 0.7%23.

Watch-outs

  • We could not confirm which construction projects need a building permit inside Colusa city limits; call the city building department at (530)458-4941 before starting52.
  • We could not confirm whether county septic permits apply inside the city; ask Colusa County Environmental Health at (530) 458-088817.
  • We could not confirm the city's owner-builder rules or which edition of the California building code the city has adopted; ask the city building department2.

Sources

  1. City of Colusa zoning information (Colusa), quoted and re-checked
  2. City of Colusa Planning and Building (cityofcolusa.com)
  3. Colusa County Onsite Wastewater Treatment Systems Ordinance, quoted and re-checked
  4. Planning and Building – City of Colusa (Colusa), quoted and re-checked
  5. Planning and Building – City of Colusa (Colusa), quoted and re-checked
  6. Colusa Code, Appendix A, Art. 5, Sec. 5.05 (Colusa), quoted and re-checked
  7. Colusa Code, Appendix A, Art. 5, Sec. 5.05 (Colusa), quoted and re-checked
  8. Colusa Code, Appendix A, Art. 5, Sec. 5.05 (Colusa), quoted and re-checked
  9. Colusa Code, Appendix A, Art. 39, Sec. 39.05 (Colusa), quoted and re-checked
  10. Colusa Code, Sec. 20-1 (Colusa), quoted and re-checked
  11. City of Colusa zoning information (Colusa), quoted and re-checked
  12. Colusa Code, Appendix A, Art. 5, Sec. 5.05 (Colusa), quoted and re-checked
  13. Colusa Code, Appendix A, Art. 6, Sec. 6.05 (Colusa), quoted and re-checked
  14. Colusa Code, Appendix A, Art. 6, Sec. 6.05 (Colusa), quoted and re-checked
  15. Commissions – City of Colusa (Colusa), quoted and re-checked
  16. Building Permits, quoted and re-checked
  17. Colusa County Environmental Health (countyofcolusaca.gov)
  18. Colusa County Onsite Wastewater Treatment Systems Ordinance, quoted and re-checked
  19. Colusa Code, Sec. 11B-20 (Colusa), quoted and re-checked
  20. Colusa Code, Appendix A, Art. 39, Sec. 39.05 (Colusa), quoted and re-checked
  21. Planning and Building – City of Colusa (Colusa), quoted and re-checked
  22. Appendix G Drainage, Hydrology, and Water Quality Analysis, quoted and re-checked
  23. Effective property tax rate: 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.

Answers from the rulebook for Colusa

Colusa’s own rules

  • InspectionsLimited

    City building projects handled by the Colusa building department.

    • The page does not specify which project types require inspection.
    “The building department issues permits, reviews plans, schedules inspections, conduct inspections, and issues a Certificate of Occupancy.”
  • Certificate of occupancyLimited

    Projects for which the City of Colusa building department issues a Certificate of Occupancy.

    • The official page does not state that every building or change of occupancy requires a certificate.
    “The building department issues permits, reviews plans, schedules inspections, conduct inspections, and issues a Certificate of Occupancy.”
  • Local zoningPresent

    Land inside Colusa city limits; the City of Colusa administers its zoning ordinance.

    “One-family dwellings, including private garages, accessory buildings and uses.”
  • Zoning districtsPartial

    Published Colusa city zoning districts and district-specific land-use controls.

    • The reviewed code publishes R-1, R-2, mixed-use, floodplain, and other district provisions; this record does not reproduce the complete zoning-district inventory.
    “Mixed Use Table Type of Use M-U-B Bridge St. M-U-D Down- town M-U-M Main St. M-U-R Residen- tial”
  • Living in an RVTemporary only (with conditions)

    Recreational vehicles placed in mapped A1-30, AH, and AE flood-hazard zones inside Colusa city limits.

    • The RV must remain fewer than 180 consecutive days and be fully licensed and ready for highway use, or it must meet the ordinance permit, elevation, and anchoring requirements for manufactured homes.

    maximum stay: < 180 consecutive days (The alternative is compliance with the ordinance permit, elevation, and anchoring requirements.)

    “All recreational vehicles placed on sites within Zones A1-30, AH, and AE on the community's flood insurance rate map will either:”
  • Camping on your landProhibited

    Camping at the City of Colusa boat launch facility between 10th and 8th Streets along Main Street.

    • The prohibition is facility-specific and does not establish a citywide camping rule.
    “To engage in any camping activities (which for the purposes of this article includes erection of tents or any other temporary living structure).”
  • Mandatory utility hookupSewer (with conditions)

    Separate premises receiving City of Colusa water service inside city limits.

    • Water service applicants must apply for connection to the city sewerage system.
    • A person may not take city water or connect a service pipe to city water mains without first connecting to city sewerage.
    • A meter application is also required.
    “No person shall take any water of the city or connect any service pipe to the city water mains, without first connecting to the city's system of sewerage pursuant to and in accordance with Chapter 15 of this Code.”
  • Subdividing landRegulated (with conditions)

    Subdivision and parcel-map applications inside Colusa city limits.

    • The Planning Commission holds public hearings for conditional use permits, subdivision, and parcel map applications.
    “this chapter establishes requirements for the preparation, filing, approval or disapproval of subdivision maps, consistent with the requirements of the map act.”
  • Building in a floodplainLimited

    New construction and substantial improvements in areas of special flood hazard inside Colusa city limits.

    • Residential construction must have the lowest floor, including basement, elevated at least one foot above base flood elevation in A and other zones; AO zones have different depth-based elevation rules.
    • Elevation must be certified by a registered professional engineer or surveyor and verified by the community building inspector.
    • On-site waste disposal systems must be located to avoid impairment or contamination during flooding.

    residential elevation above base flood elevation: >= 1 foot (AO zones use the specified depth number or three feet where no depth number is specified.)

    “In an A zone, elevated at least one foot above the base flood elevation, as determined by the City of Colusa.”
  • Permit processPartial

    City building-permit processing inside Colusa city limits.

    • The city page directs applicants needing forms, permits, or inspections to contact the building department.
    • The page does not publish a complete application checklist or processing timeline.
    “To access the forms and documents, need to submit a permit, or schedule an inspection, please contact:”

Rules another office applies inside Colusa

Colusa does not set these itself; the county, a health district or the state does, and they apply to every address inside its limits.

  • Minimum lot sizeSpecified

    R-2 Two Family Residence District inside Colusa city limits.

    • Single-family and duplex lots have different minimum areas; lot dimensions also vary by interior and corner lot.

    single-family minimum lot area: >= 6000 square feet (Duplex minimum is 7000 square feet.) · duplex minimum lot area: >= 7000 square feet

    “Lot Areas: Six thousand square feet for single family dwellings. Seven thousand square feet for duplex dwellings.”
    One more reviewed finding on this topic
    • Specified — R-1 Single Family Residence District inside Colusa city limits.
      “Lot Area: Eight thousand square feet. (b) Lot Dimensions: Eighty feet wide; one hundred feet deep.”
  • SetbacksSpecified

    R-1 Single Family Residence District inside Colusa city limits.

    • Interior and corner lots have different side-yard rules; rear yard is percentage-based with minimum and maximum.

    front setback: 20 feet · interior side setback: 5 feet on one side and 10% of lot width on the other (Total of both need not exceed 15 feet.) · rear setback: 20% of lot depth (May not be less than 15 feet and need not exceed 30 feet.)

    “Front Yard Setback: Twenty feet. (e) Side Yard Setback: 1. Interior Lots: Each interior side yard shall be not less than five feet on one side and ten percent of the lot width on the other side, but the total of both need not exceed fifteen feet. [...] (f) Rear Yard Setback: Twenty percent of the lot depth; may not be less than fifteen feet, need not exceed thirty feet.”
    One more reviewed finding on this topic
    • Specified — R-2 Two Family Residence District inside Colusa city limits.
      “Front Yard Setback: Twenty feet. [...] Rear Yard Setback: Twenty percent of lot depth, may not be less than fifteen feet, need not exceed thirty feet.”
  • Lot coverageSpecified

    R-1 Single Family Residence District inside Colusa city limits.

    maximum main building coverage: <= 35 percent of lot area

    “Maximum Main Building Coverage: Thirty-five percent of lot area.”
    One more reviewed finding on this topic
  • Building heightSpecified

    R-1 Single Family Residence District inside Colusa city limits.

    maximum height: <= 35 feet (Two and one-half stories maximum.)

    “Building Height Limit: Two and one-half stories, but not to exceed thirty-five feet.”
    One more reviewed finding on this topic
    • Specified — R-2 Two Family Residence District inside Colusa city limits.
      “Building Height Limit: Two and one-half stories, but not to exceed thirty-five feet.”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission; ask Colusa or Colusa County directly.

  • Building permit — Construction inside Colusa city limits.
  • Owner-builder exemption — Owner-builders undertaking construction inside Colusa city limits.
  • Building code adopted — Building construction inside Colusa city limits.
  • Minimum dwelling size — Residential districts inside Colusa city limits.
  • Tiny homes — Tiny-home occupancy inside Colusa city limits.
7 more unanswered
  • Who permits septic
  • Septic permit
  • Septic inspection
  • Off-grid sanitation
  • Well permit
  • Agricultural exemption
  • Short-term rentals

Each answer was extracted from an official source and independently re-checked against that source by a second reviewer. That is an evidence check, not legal advice. Rules change; confirm with the authority before you buy or build.

Unanswered questions are usually a sign that Colusa publishes no rule on the point, not that none exists. Colusa County’s page lists the county offices to call.

← All of Colusa County: county rules, score and offices