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

Unincorporated Monterey County requires a construction permit for nearly any structure, including a new home, an addition or most outbuildings¹. Some uses and structures also need a separate planning permit even when a construction permit is not required¹¹. Monterey County's housing element records the county's adoption of the 2022 California Building Code and related state codes, subject to county provisions and local amendments³. California's 2025 Building Standards Code applies statewide to permit applications filed on or after January 1, 2026, so ask Building Services which code cycle and local amendments govern your filing^11,12. Building permit fees follow the county's fee schedule adopted February 3, 2026, and vary by project type and construction valuation; single-family plan check costs 65% of the building inspection fee, and the schedule adds a 15% General Plan Management Fee and a 13% Technology Fee¹³. Which permits apply also depends on the zoning district and proposed use because separate inland and coastal zoning ordinances cover unincorporated land³.

Monterey County's building department is Housing & Community Development (HCD) Building Services, part of the county's Permit Center at 1441 Schilling Place, 2nd Floor, Salinas, CA 93901¹¹. Reach the Permit Center at (831) 755-5025; the county's own FAQ page gives Permit Center hours as 8 am to 4 pm, Monday through Friday¹¹. The same Permit Center houses Planning Services, so a call to (831) 755-5025 can route you to either building or planning staff depending on what your project needs¹¹. Development Services, also based at the Schilling Place office, issues encroachment permits for any driveway or other work that crosses a county road right-of-way¹⁴. A driveway onto a county highway needs a written permit from the Public Works Director, and the driveway may not sit within an intersection's curve returns¹⁵. The encroachment application expires 365 days after filing unless a permit issues, and inspection must be scheduled at least 48 hours before work¹⁵. If a parcel sits near mapped water, Permit Center staff at the same office determine whether it falls inside a FEMA Special Flood Hazard Area before you design a foundation¹⁶.

Monterey County zones its unincorporated land, with Title 21 setting standards inland and Title 20 in the coastal zone^2,3. Those rules stop at city limits: Salinas and Soledad set their own zoning^17,18, while septic and wells for every address stay with county or state health authorities⁴. Minimum lot size runs from about 5,000 square feet in a High Density Residential district up to 40–160 acres in agricultural and grazing districts¹⁰. Setbacks, lot coverage and building height also vary by district and may be affected by special standards or exceptions¹⁰. Inland ADUs and junior ADUs are allowed only in qualifying zoning districts and remain subject to building, zoning, wastewater and other permits; Monterey County also prohibits ADUs in some unincorporated areas where water or sewer service is inadequate or traffic and safety impacts prevent them³. Land the zoning maps do not name falls in the U District². We found no general minimum home size; the one size rule we confirmed covers single-room-occupancy units in HDR districts, which need a Use Permit and run 150 to 400 square feet excluding bathroom and closet, for no more than two people³. The coastal version of that rule is a public draft, so ask Planning Services whether it has been adopted^11,19. Along the Carmel River in Carmel Valley, development within 200 feet of the riverbanks, in the floodway or in the riparian corridor is prohibited unless a stated exception is met, and all development within 200 feet of the banks needs a Use Permit²⁰. Planning Services can identify the zoning designation through its lookup system or by phone before you design around a parcel¹¹.

The Monterey County Environmental Health Bureau regulates onsite wastewater treatment systems in the unincorporated county under the county's approved Local Agency Management Program⁴. A county installation permit is required for an OWTS handling domestic wastewater discharge of 10,000 gallons per day or less⁴. Off-grid does not mean permit-free: constructing, replacing, modifying or abandoning an OWTS requires applicable permits, and most onsite treated nonpotable-water systems need a county plumbing permit before installation⁴. Only 2.6% of Monterey County soils are rated free of severe limits for a conventional drain field, so establish wastewater feasibility before committing to a building site⁵. The Environmental Health Bureau's Land Use program reviews development projects and building permits for compliance where the bureau has oversight²¹. A final inspection is required before piping or components are covered with earth, requests need at least 48 hours' notice, and the system may not be used until the Environmental Health Bureau grants final approval⁴. A structure within 300 feet of a sewer main generally must connect to it, unless it is served by a lawfully functioning OWTS or another listed exception applies⁴. Repairs as defined in Chapter 15.20 do not need an OWTS installation permit⁴. Wells are a separate matter: a groundwater monitoring boring used for septic site evaluation that stays in place more than 72 hours needs its own county monitoring-well permit⁴. The county's rules for a domestic water well were not confirmed; California leaves well permitting to local enforcing agencies such as the county environmental health department²². The county may also require an operating permit when routine monitoring or maintenance is necessary⁴.

Monterey County prohibits using a trailer, camper, RV or boat as a dwelling or temporary guest room while it is parked or stored on private property in the unincorporated county⁸. A tiny home has no single countywide path: its legal treatment depends on whether it qualifies as approved housing, a manufactured home or an ADU and whether the parcel's zoning and services support that use^3,23. Inland ADUs remain subject to building, zoning and wastewater approvals and are prohibited in some areas with inadequate water or sewer service or traffic and safety constraints³. A separate coastal ordinance can allow a qualifying tiny home or manufactured home (as defined in California Health and Safety Code section 18007) as an ADU in listed coastal districts, but only with Environmental Health Bureau approval of sewage and water and not until the Coastal Commission certifies it and the county confirms the Board's action⁹. Ask Planning Services to classify the unit and confirm the parcel before buying it¹¹.

1. Confirm the zoning district and its lot-area, setback, coverage and height standards with HCD Planning Services^10,11.
2. Ask Permit Center staff whether the parcel is in a FEMA Special Flood Hazard Area before designing the foundation¹⁶.
3. Establish water and wastewater feasibility with the Environmental Health Bureau; off-grid sanitation still requires applicable OWTS or plumbing permits^4,21.
4. Apply through HCD Building Services for the construction permit and any separate planning permit the use requires¹¹.
5. Apply for an encroachment permit if the driveway or other work enters a county road right-of-way¹⁴.
6. If building as an owner-builder, review the county's owner-builder notice before hiring labor⁶. State law exempts an owner from contractor licensing when none of the work is intended or offered for sale and the owner does it personally or hires licensed trade contractors directly; for single-family projects no more than four structures may be offered for sale in a calendar year, and a homeowner improving a principal residence must have lived there for 12 months before completion⁷. That exemption does not waive building permits, inspections, zoning or septic approvals⁷.
7. Before final inspection, file the construction and demolition waste recycling report; skipping it can delay the Certificate of Occupancy or final inspection²⁴.

Monterey County sits about 24 miles from the nearest city of 100,000 or more, with a countywide population density of 131 people per square mile, so how rural a parcel feels depends heavily on which part of the county it's in⁵. About 45% of the land is wooded and roughly a quarter sits at a gentle 15% slope or less, so check a specific parcel's terrain and tree cover, not just the county average, before assuming it's buildable⁵. Federal land covers about 26% of the county, so confirm a parcel's boundaries against public land before you buy⁵. The county gets about 21 inches of rain a year and has seen severe drought in roughly a third of recent years, which matters for a private well⁵. We could not confirm the county's permit rules for a domestic well, so ask the Environmental Health Bureau before drilling^21,22. Typical home value here is $854,719 and farmland runs about $12,799 an acre, well above what many rural buyers expect, and a typical property tax bill is $4,782 a year at an effective rate of 0.7%⁵. Because nearly all of the county's soils rate poorly for a conventional septic drain field, budget for a site evaluation and likely an engineered system before you close⁵.