Bolthole Index

Sonoma County, California

Building permits, zoning and land rules in Windsor, California

Inside the Town of Windsor in Sonoma County, California, building-permit applications go to the Town Permit Center, and Windsor administers its own zoning code12. Permit Sonoma handles well permits countywide and permits non-standard onsite wastewater systems, including systems within incorporated cities34.

At a glance

Building permits
Apply online through Windsor's eTRAKiT Permit Center1
Zoning
Windsor administers its own Title 17 Zoning Code2
Tiny homes
Allowed by right with zoning clearance in listed residential zones5
Accessory dwellings
Allowed by right with zoning clearance in listed residential zones6
Septic
Permit Sonoma administers non-standard onsite-system permits countywide4
Private wells
County permit required to drill, deepen or abandon a well3
RV living
Permanent occupancy is generally not allowed unless a local ordinance provides otherwise7

Who to call

Building permits

Town of Windsor Building Division

Building-permit applications and building forms for property inside Windsor town limits

707-836-2304

[email protected]

9291 Old Redwood Hwy #400, Windsor, CA 95492

Online permits →

Zoning

Town of Windsor Planning Division

Zoning, development review and planning applications inside Windsor town limits

707-838-1021

9291 Old Redwood Hwy, Bldg. 400, Windsor, CA 95492

Online permits →

Septic permits

Permit Sonoma - Well and Septic Division

Well permits and septic-system site, design, repair, upgrade and inspection work in Sonoma County

(707) 565-2849

[email protected]

Contact details are copied from each office’s official page and were checked against it on October 10, 2026.

Off-grid gear

Going off-grid in Town of Windsor means bringing your own water and power. The kit we’d start with:

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Do you need a building permit in Windsor, California?

Windsor publishes a building-permit process for projects inside town limits: applications go online through eTRAKiT, where the Town provides its building application and owner-builder, contractor and special-inspection forms18. California also requires a separate permit before covered construction, alteration, repair, movement, improvement, removal, conversion or demolition work begins9. The Town's page does not identify every exempt project, so ask the Windsor Building Division whether your exact scope needs a building permit8.

The statewide building standards now apply to buildings and structures whose permit applications date from 2026 onward10. Acting as an owner-builder does not erase the permit requirement: California's licensing exemption is conditional, and owner-builder projects still must pass applicable codes and inspections1112.

Who issues building permits in Windsor, and how do you reach them?

The Town of Windsor Building Division is the building-permit contact for a Windsor address; apply through eTRAKiT, call 707-836-2304 or email [email protected]8. The counter is at 9291 Old Redwood Hwy #400 in Windsor8.

Zoning questions go to the separate Town of Windsor Planning Division at 707-838-1021 in Building 400 at the same Town Hall campus13. The Planning Division reviews housing and commercial development projects, while the Building Division supplies the building-permit application route138.

Do not send a Windsor building or zoning application to Permit Sonoma: Sonoma County's planning authority described in the county material applies to unincorporated land, while Windsor adopts and administers its own zoning code142.

Does Windsor have zoning, and what does it mean for tiny homes and setbacks?

Yes. Windsor administers Title 17 as its zoning code and publishes a map identifying residential, commercial, industrial and special-purpose zones215. Tiny homes and accessory dwelling units are allowed by right with zoning clearance in the listed RR, ER, SR, VR, MDR and CR residential zones, subject to their additional chapter standards56.

For a detached residential accessory structure, Windsor requires at least a 5-foot side and rear setback, prohibits encroachment into the required front setback and applies the district's street-side setback on a corner parcel16. Such a structure is limited to 15 feet high and may not exceed the primary structure's height unless the owner obtains a Minor Use Permit before the building permit17. Minimum lot area, lot coverage and minimum primary-home size depend on rules not confirmed here; call Planning for the parcel's district standards13.

How do septic and well permits work inside Windsor?

Permit Sonoma's Well and Septic Division reviews development proposals that rely on wells or septic systems and reviews septic repair or upgrade applications18. Permit Sonoma also requires an operating permit for a non-standard onsite wastewater treatment system, and its program covers incorporated cities in Sonoma County194. Every new or replacement septic system in California requires approval through the responsible local jurisdiction or regional water board20.

Where public sewer is unavailable, Sonoma County says a homeowner must install a septic system to treat household wastewater21. Only 2.8% of Sonoma County soils lack severe limitations for a conventional drain field, so a site evaluation may point toward a more complex design22.

Permit Sonoma also requires a county permit to drill, deepen or abandon a well inside incorporated cities, and only a C-57 well-drilling contractor can receive it3. Call (707) 565-2849 before relying on onsite water or wastewater18.

Can you live in an RV or tiny home on land in Windsor?

A tiny home can be an allowed-by-right use with zoning clearance in Windsor's listed residential zones, but Chapter 17.102 supplies additional standards5. California also requires a tiny home to qualify and receive approval as one of the recognized housing or vehicle types before it may be occupied23.

An RV is different. California says RVs are not intended as permanent dwellings and generally may be occupied only in mobilehome or special-occupancy parks unless a local ordinance allows otherwise7. Windsor's flood-hazard rule lets an RV in Zones A1-30, AH or AE use one compliance path by staying fewer than 180 consecutive days; the alternatives concern highway readiness or permit, elevation and anchoring compliance, not blanket residential approval24. Windsor's public-property camping ban does not answer private-lot occupancy25. Ask Planning before placing or occupying an RV on a private parcel13.

Building a home in Windsor: the steps, in order

  1. Ask Windsor Planning to identify the parcel's zone and confirm the proposed home's use, setbacks, lot standards and any zoning clearance132.
  2. Determine whether public sewer and water serve the parcel; if not, ask Permit Sonoma to review the proposed septic system and well18.
  3. Prepare the building application, plans and the Town's applicable owner-builder, contractor and special-inspection forms1.
  4. Submit the building-permit application online through Windsor's eTRAKiT portal18.
  5. Complete required building inspections; an owner-builder project must pass applicable codes and inspections26.
  6. If access encroaches on a state highway right of way, obtain a Caltrans encroachment permit27.

What stays with Sonoma County, and what should you check before buying?

Windsor controls zoning and the building-permit application inside town limits, while Permit Sonoma remains the contact for onsite wells and septic systems2118. County zoning rules for unincorporated Sonoma County should not be applied to a Windsor parcel14.

Before buying, confirm the parcel's district, tiny-home classification, setbacks, public sewer availability and flood zone with the responsible offices1318. The Town regulates subdivisions, with its residential table distinguishing smaller and larger small-lot projects and directing applicants to additional standards28. Non-hosted short-term rentals are prohibited in the listed Windsor residential zones29.

For county-level context, Sonoma County's effective property-tax rate is 0.7%, and the typical home value is about $798,7373031.

Watch-outs

  • Windsor's rules apply inside town limits; Sonoma County building and zoning rules for unincorporated parcels are not substitutes214.
  • Non-hosted short-term rentals are prohibited in Windsor's listed residential zones29.
  • Private-lot RV occupancy, minimum primary-home size, residential minimum lot area and lot coverage should be confirmed with Windsor Planning before purchase13.

Sources

  1. Permit Center (Town of Windsor), quoted and re-checked
  2. Planning Documents (Town of Windsor), quoted and re-checked
  3. Permit Sonoma Well Permits (Town of Windsor), quoted and re-checked
  4. Permit Sonoma Non-Standard Onsite Wastewater Treatment Systems (OWTS) Permits, quoted and re-checked
  5. 17.10.030 Residential Zones Land Use Regulations and Allowable Uses (Town of Windsor), quoted and re-checked
  6. 17.10.030 Residential Zones Land Use Regulations and Allowable Uses (Town of Windsor), quoted and re-checked
  7. hcd.ca.gov (California statewide rule), quoted and re-checked
  8. Town of Windsor Building Division (townofwindsor.ca.gov)
  9. Do I need a building permit for my project? (California statewide rule), quoted and re-checked
  10. Approved Building Standards (California statewide rule), quoted and re-checked
  11. California Business and Professions Code Section 7044 (California statewide rule), quoted and re-checked
  12. Owner-Builder Responsibilities (California statewide rule), quoted and re-checked
  13. Town of Windsor Planning Division (townofwindsor.ca.gov)
  14. Sonoma County GIS Zoning Layer, quoted and re-checked
  15. Planning Documents (Town of Windsor), quoted and re-checked
  16. 17.40.200 Residential Accessory Structures and Uses (Town of Windsor), quoted and re-checked
  17. 17.40.200 Residential Accessory Structures and Uses (Town of Windsor), quoted and re-checked
  18. Permit Sonoma - Well and Septic Division (permitsonoma.org)
  19. Permit Sonoma Non-Standard Onsite Wastewater Treatment Systems (OWTS) Permits, quoted and re-checked
  20. 2023 OWTS Policy (California statewide rule), quoted and re-checked
  21. Permit Sonoma Septic Permits (Town of Windsor), quoted and re-checked
  22. 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
  23. Information Bulletin 2016-01: Tiny Homes (California statewide rule), quoted and re-checked
  24. 9-1-550 Standards for Recreational Vehicles (Town of Windsor), quoted and re-checked
  25. 3-10-2110 Camping on Public Property Prohibited at All Times (Town of Windsor), quoted and re-checked
  26. Owner-Builder Responsibilities (California statewide rule), quoted and re-checked
  27. Encroachment Permits | Caltrans (California statewide rule), quoted and re-checked
  28. 17.10.030 Residential Zones Land Use Regulations and Allowable Uses (Town of Windsor), quoted and re-checked
  29. 17.10.030 Residential Zones Land Use Regulations and Allowable Uses (Town of Windsor), quoted and re-checked
  30. Effective property tax rate: Bolthole Index county data
  31. Typical home value (Zillow): Bolthole Index county data

Written October 10, 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 Town of Windsor

Town of Windsor’s own rules

  • InspectionsLimited

    Existing residential accessory structures used as temporary housing inside Windsor town limits.

    • Inspection by the Building Official and Windsor Fire Protection District staff is required before occupancy as a temporary housing unit.
    “The structure shall be subject to inspection by the Building Official and Windsor Fire Protection District staff prior to occupancy as a temporary housing unit.”
  • Local zoningPresent

    Windsor town limits; the Town adopts and administers its own Title 17 Zoning Code.

    • The Town's official planning page identifies Title 17 as the Town's incorporated Zoning Code.
    “The Zoning Code was updated in November 2024 and incorporated into the Town's Municipal Code as Title 17.”
  • Zoning districtsPublished

    Land inside Windsor town limits.

    • The Town publishes a zoning map and Title 17 zoning code.
    • Residential districts identified in the cited table include RR, ER, SR, VR, MDR, and CR.
    “The Zoning Map identifies residential, commercial, industrial, and special purpose zones in the Town. This map is used in conjunction with the Zoning Code.”
  • SetbacksSpecified

    Detached residential accessory structures inside Windsor town limits.

    • No required front-yard setback may be encroached.
    • Side and rear setbacks are at least five feet, except corner parcels must maintain the applicable street-side setback.
    • Attached structures follow the primary structure's applicable setbacks.

    side and rear setback: >= 5 feet (Corner parcels must maintain the street-side setback required by the applicable zoning district.)

    “Accessory structures shall not be located within a required front yard setback, and shall maintain side and rear yard setbacks of at least five (5) feet, except that accessory structures on corner parcels shall maintain the street side setback required by the applicable zoning district.”
  • Building heightSpecified

    Detached residential accessory structures inside Windsor town limits.

    • Height may not exceed the primary structure's height.
    • Requests to exceed or deviate from the height requirement require a Minor Use Permit before Building Permit.

    accessory structure height: <= 15 feet (May not exceed the height of the primary structure.)

    “The height of an accessory structure shall not exceed fifteen (15) feet. In no case shall the accessory structure height exceed the height of the primary structure.”
  • Camping on your landProhibited

    Camping on public property inside Windsor town limits.

    • Exception for a designated public campground or written Town permit.
    • Additional public-property locations and time restrictions are stated in Section 3-10-2110 and Section 3-10-2120.
    “It shall be unlawful at all times of the day for any person or persons to camp in all type of public property listed herein, except in a designated public campground or by authority of a written permit issued by the Town on any public property:”
  • Tiny homesAllowed (with conditions)

    Tiny homes in Windsor residential zones RR, ER, SR, VR, MDR, and CR.

    • Table 17.10-01 marks Tiny Home P in all listed residential zones.
    • Allowed-by-right uses require a Zoning Clearance under Section 17.10.030.D.
    • Chapter 17.102 contains additional tiny-home standards.
    “Tiny Home P P P P P P 17.102 (Tiny Homes)”
  • Accessory dwellingsAllowed (with conditions)

    Accessory dwelling units in Windsor residential zones RR, ER, SR, VR, MDR, and CR.

    • Table 17.10-01 marks Accessory Dwelling Unit P in all listed residential zones.
    • Allowed-by-right uses require a Zoning Clearance under Section 17.10.030.D.
    • Chapter 17.82 supplies additional ADU regulations.
    “Accessory Dwelling Unit P P P P P P 17.82 (Accessory Dwelling Unit (ADU))”
  • Subdividing landRegulated (with conditions)

    Residential subdivision and small-lot subdivision inside Windsor town limits.

    • Small-lot subdivision standards apply in SR, VR, and MDR zones.
    • The Town's fee schedule separately lists minor and major subdivision applications.
    “Small Lot Subdivision, 4 or fewer lots — — MUP MUP MUP — 17.88 (Small Lot Subdivision) Small Lot Subdivision, 5 or more lots — — CUP CUP CUP — 17.88 (Small Lot Subdivision)”
  • Building in a floodplainLimited

    Recreational vehicles and manufactured homes in mapped flood-hazard Zones A1-30, AH, and AE inside Windsor town limits.

    • RVs must either remain fewer than 180 consecutive days, be fully licensed and ready for highway use, or satisfy specified permit, elevation, and anchoring requirements.
    • Manufactured homes must meet elevation, anchoring, and certification requirements.

    maximum RV stay under one option: < 180 consecutive days (Alternative compliance options are available.)

    “All recreational vehicles placed in Zones A1-30, AH, and AE will either: 1. Be on the site for fewer than one hundred eighty (180) consecutive days; or 2. Be fully licensed and ready for highway use. [...]; or 3. Meet the permit requirements of Section 9-1-455 of this chapter and the elevation and anchoring requirements for manufactured homes in Section 9-1-545 (a).”
  • Short-term rentalsProhibited

    Non-hosted short-term rentals in Windsor residential zones RR, ER, SR, VR, MDR, and CR.

    • The cited table marks non-hosted short-term rentals not allowed in all listed residential zones.
    “Short-Term Rental, Non-Hosted — — — — — — 17.40.260 (Short-Term Rentals)”
  • Permit feesPublished

    Town planning, zoning, subdivision, short-term-rental, and related permit fees inside Windsor town limits.

    • Fee schedules are reviewed and updated annually.
    • The cited schedule is FY2025-26; the Town page also lists a current FY2026-27 schedule.

    minor subdivision/reconfiguration fee: 4755 USD per application · major subdivision fixed fee: 7000 USD per application (plus $30 per lot) · short-term-rental initial application: 595 USD per application · short-term-rental renewal: 238 USD per application

    “Minor Subdivision/Reconfiguration $ 4,755.00 per application [...] Fixed Fee $ 7,000.00 per application plus: Variable Fee $ 30.00 per lot [...] License - Initial Application $ 595.00 per application [...] License - Renewal $ 238.00 per application”
  • Permit processPublished

    Building-permit applications inside Windsor town limits.

    • Applications are submitted online through eTRAKiT.
    • The Town page lists building applications, owner/builder forms, licensed-contractor forms, and special-inspection forms.
    “Apply for all building permits online on eTRAKiT!”

Rules another office applies inside Town of Windsor

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

  • Off-grid sanitationLimited

    Wastewater disposal inside Windsor town where public sewer is unavailable.

    • The County source states that homeowners must install septic systems where public sewer is unavailable; it does not establish a general authorization for other off-grid sanitation methods.
    “In areas where public sewer is not available, homeowners MUST have septic systems installed on their property that will treat wastewater coming from their home.”
  • Well permitRequired

    Drilling, abandoning, or deepening wells inside Windsor town limits.

    • The source covers incorporated lands/cities.
    • Permits can only be issued to C-57 Well Drilling Contractors.
    “Well permits are required to drill, abandon, or deepen wells and can only be issued to C-57 Well Drilling Contractors.”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission; ask Town of Windsor or Sonoma County directly.

  • Building permit — Building work inside Windsor town limits.
  • Owner-builder exemption — Owner-builders applying for construction permits inside Windsor town limits.
  • Certificate of occupancy — Occupancy of buildings inside Windsor town limits.
  • Minimum dwelling size — Primary dwellings inside Windsor town limits.
  • Minimum lot size — Residential lots inside Windsor town limits.
6 more unanswered
  • Lot coverage
  • Septic permit
  • Septic inspection
  • Mandatory utility hookup
  • Agricultural exemption
  • Driveway access

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 Town of Windsor publishes no rule on the point, not that none exists. Sonoma County’s page lists the county offices to call.

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