Building permits, zoning and septic rules in Ventura County, California

Yes. Buildings and structures in unincorporated Ventura County generally need a permit from RMA Building and Safety before construction starts, but some small storage sheds, flooring and most residential finish work are exempt; public schools, hospitals, utility infrastructure and public-right-of-way projects also fall outside the ordinary county permit rule¹. Work that needs a permit is inspected by the Building Division: the owner or contractor calls for each inspection, and required work must stay exposed until the Building Official approves it¹³. California's owner-builder exemption concerns contractor licensing, not the permit or inspection requirements⁵. In Ventura County, the owner-builder permit is taken out in the owner's name, and Building and Safety requires a signed Notice to Property Owner acknowledging liability, plus verified owner identification, before issuing it⁶.

RMA Building and Safety issues building permits for unincorporated Ventura County only¹. Inside Camarillo and Fillmore, the city's own office handles building permits^14,15; in every other incorporated city, call that city's building department. RMA Building and Safety is at 800 S Victoria Ave, Ventura, CA 93009, phone (805) 654-2494, and permits can also be tracked through the county's OneStopPermits portal¹. Construction in unincorporated Ventura County is governed by the 2025 Ventura County Building Code, which adopts the current California Building Standards Code with county-specific amendments¹⁶. Fees aren't a flat number: Building and Safety calculates them based on the size, scope and value of your specific project during the permitting process¹⁷.

Yes. Every parcel in unincorporated Ventura County has a county zoning designation². RMA Planning applies the Coastal Zoning Ordinance in the Coastal Zone and the Non-Coastal Zoning Ordinance elsewhere; the two codes differ in substantive ways³. Inside Camarillo, Fillmore, Simi Valley and Port Hueneme, the city's own code sets zoning instead^18,19,20,21. In the Non-Coastal ordinance, lot coverage, setbacks and height are set district by district, so no single countywide number applies². Setbacks are an example: RA zoning requires 5 feet on the interior side and 10 feet at the rear, while OS-REC requires 20 feet at the front². Height in OS-REC starts at 25 feet and can rise to 35 feet when each side-yard setback is at least 15 feet². Greenhouses and similar plant-growing structures on agriculturally designated lots are excluded from the lot-coverage maximum². In the non-coastal area, an accessory dwelling unit can be approved directly with a building permit, and a manufactured home can serve as the ADU^22,23. For minimum home size, Ventura County's reviewed materials show no separate local rule; California's efficiency-unit standard calls for at least 190 square feet of living space, or 150 square feet if a local ordinance allows it¹⁰.

RMA Environmental Health is the OWTS authority for unincorporated Ventura County; the city building department is the contact for systems inside city limits, while mobile home park systems are outside the county division's jurisdiction⁴. Septic permits stay with Environmental Health or the city, never with RMA Building and Safety, even where a city issues its own building permits. Off-grid sanitation is possible through an OWTS where public sewer is unavailable, but every new system needs an individual site evaluation before a Permit to Construct is issued⁴. Septic permits and inspections cover both new systems and repairs^4,24. A property requiring a conventional OWTS must connect when an available public sewer line is within 200 feet²⁵. For an alternative OWTS, the public-sewer connection threshold is one-half mile²⁵. Only about 11.1% of county soils avoid severe limits for a conventional drain field, so establish feasibility early¹².

Ventura County's confirmed RV-on-private-land allowances are tied to construction, not a general right to live in an RV. In the unincorporated non-coastal area, a Zoning Clearance may authorize one habitable RV for up to 12 months during permitted construction or major remodeling of a principal dwelling, with up to two additional 12-month periods for substantial progress². The Coastal Zone allows an owner's RV for 12 months during permitted home construction, with one additional 12-month period for substantial progress and required permanent water and sewage connections⁷. In non-coastal RV parks, each RV or its occupants may stay no more than 90 days in any 120-day period; those parks require a Conditional Use Permit and are limited to specified zones^2,8. A tiny home outside the manufactured-home, factory-built, RV, park-trailer or camping-cabin classifications is a dwelling and must comply with the California Building Standards Code for legal occupancy⁹. Tiny-home-style RVs, travel trailers and truck campers in non-coastal RV parks share that limit; such parks need at least 3 acres on one legal lot, allow no permanent structure attached to a space, and are allowed only in OS-REC, OS, RA and RE zones with a Conditional Use Permit². Manufactured homes may be dwellings in an authorized unincorporated mobilehome park, subject to the overlay, base-zone, building and state requirements²⁶. Ventura County has not confirmed a general rule for overnight camping outside parks or construction allowances; ask RMA Planning about the parcel and unit³.

1. Confirm the parcel's Coastal or Non-Coastal zoning with RMA Planning, and determine whether any proposed lot split or lot-line adjustment must follow the county Subdivision Ordinance^3,27.
2. If you need a well, ask about restrictions in the parcel's groundwater basin; local moratoria may remain even though the countywide unincorporated-area moratorium was lifted¹¹.
3. If public sewer is unavailable, obtain a site-specific OWTS evaluation from RMA Environmental Health before fixing the site plan⁴.
4. Apply through RMA Building and Safety under the 2025 Ventura County Building Code, and sign the Owner-Builder Declaration if applicable^1,6,16. Call for each inspection and keep required work exposed until it passes¹³.
5. If the site lies in a FEMA-designated 1% annual-chance floodplain, obtain a Floodplain Development Permit before construction²⁸.

Confirm the parcel's Coastal or Non-Coastal zoning and whether a proposed division, merger or lot-line adjustment triggers the Ventura County Subdivision Ordinance^2,27. In the Non-Coastal Zoning Ordinance, minimum lot area runs by district: RA is 1 acre, OS is 10 acres and AE is 40 acres, so confirm the district before assuming a parcel can be split². For wastewater, only about 11.1% of county soils avoid severe limits for a conventional drain field, and each new OWTS needs site-specific evaluation^4,12. Check the groundwater basin because local well moratoria may remain¹¹. A FEMA 1% annual-chance floodplain designation requires a development permit for habitable and non-habitable structures²⁸. About 52% of the county is federal land, which limits the private rural inventory¹². The effective property-tax rate is about 0.7%, and the median annual bill is about $5,326¹².