Buying Land in California: Zoning, Legal Lots, Septic, Wells and Access

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

Buying land in California is mostly a question of whether you can build what you want on it. Before you commit, confirm the parcel’s general plan and zoning, that it is a legal lot under the Subdivision Map Act, that the county will approve a septic system and well (or that sewer and water are available), that you have legal access, and whether fire safe rules or a Williamson Act contract apply. Most of those answers come from the county planning and environmental health offices, the preliminary title report and a survey.

This guide walks through each check in the order we usually work through them for clients, with notes on the counties Diamond serves. It applies to rural home sites, infill lots and agricultural acreage alike.

Step 1: General plan and zoning

Every California city and county must adopt a long-term general plan for physical development under Government Code 65300, and Government Code 65860 requires zoning to be consistent with that plan. In practice you check both:

• General plan land use designation: the long-range intent (rural residential, agricultural, resource, urban).
• Zoning district: the rules that apply today, including permitted and conditional uses, minimum lot size, density, setbacks and height.
• Overlays and combining districts: such as flood, scenic, riparian or historic overlays that add conditions.

Ask the planning department for the parcel’s zoning and any open code enforcement or permit history. In Sonoma County, for example, agricultural and resource zones have their own use rules; our Sonoma County agricultural zoning guide covers them. If you are thinking about splitting the parcel later, read our guide to subdividing land in Sonoma and Napa before you buy.

Step 2: Is it a legal lot? The Subdivision Map Act

The Subdivision Map Act controls how land is divided. A parcel with its own assessor’s parcel number is not automatically a legally created lot, and an illegally created parcel can face problems getting permits.

Government Code 66499.35 gives a property owner, or a buyer under a purchase contract, the right to ask the city or county to determine whether the parcel complies with the Map Act and local ordinances:

• If it complies, the agency records a certificate of compliance with the county recorder, and may charge a reasonable fee.
• If it does not, the agency issues and records a conditional certificate. The conditions must be satisfied before a later development permit or approval is issued, and they bind future owners.
• A recorded final map, parcel map, official map or approved certificate of exception serves as a certificate of compliance for the parcels it describes.
• A certificate addresses Map Act compliance only. The statute requires it to say the parcel may still need permits to be developed.

If the lot was created by a recorded subdivision or parcel map, the title officer and planning staff can usually confirm that quickly. Older parcels created by deed alone are the ones to check carefully.

Step 3: Septic, percolation and wells

Where there is no public sewer, you will need county approval for an onsite wastewater treatment system (OWTS). The State Water Resources Control Board’s OWTS Policy (current version adopted April 18, 2023) sets the statewide framework, and county environmental health or permit offices apply it locally.

Sonoma County shows how the local process works:

• Site evaluation. Permit Sonoma’s septic site evaluation covers soil profile evaluations (pre-percs), percolation testing and groundwater determinations under a permit number beginning "WSR." An approved WSR is required before the county will take an application for a new or replacement septic system.
• Wet-season evaluation. A septic proposal can require seasonal groundwater observations or soil testing. Review the current Permit Sonoma OWTS guidance with the county and a qualified septic designer before setting investigation deadlines. The parcel’s soils and proposed system determine the required evaluation; a dry-season visit alone does not establish approval.
• Certified tests. Percolation tests must be certified by a Registered Civil Engineer or Registered Environmental Health Specialist.
• Vesting. A vesting certificate protects an approved septic design for 3 years, or an installed approved system for 2 years, against later regulation changes, and transfers with the property.
• Records. Permit Sonoma keeps septic records back to the early 1960s and well records to the early 1970s by address. Well logs are confidential under state law, so the seller (as owner) may need to request them.

Other counties use different forms and seasons. Napa County requirements are covered on our Napa wells, septic and groundwater page. For any parcel, write a contingency long enough to complete the county’s testing, and ask environmental health what a building permit will require for water supply.

Step 4: Access and easements

Physical access is not the same as legal access. A dirt road onto the parcel may cross a neighbor’s land without any recorded right to use it. Check:

• whether the parcel fronts a public road or relies on a recorded easement;
• the easement’s width, permitted uses and any road maintenance agreement; and
• recorded easements running across the parcel for utilities, other owners’ access or drainage.

The preliminary title report lists recorded easements, and a survey shows where they sit on the ground. Easements that are used but unrecorded will not appear in the title report, which is one reason to walk the land and order a survey.

Step 5: Fire safe regulations for building

If the parcel is in a State Responsibility Area (SRA) or in a Very High Fire Hazard Severity Zone in a local responsibility area, new construction must meet the State Minimum Fire Safe Regulations adopted under Public Resources Code 4290. The Board of Forestry’s fact sheet (November 2022) explains that the rules, in place since 1991, cover:

• road standards for fire equipment access;
• signs identifying streets, roads and buildings;
• minimum private water supply reserves for emergency fire use; and
• fuel breaks and greenbelts.

Local agencies may enforce stricter requirements. Road and driveway standards can be expensive on hillside parcels, so ask the county fire marshal or fire district what will be required before you close. Our guide to fire hazard severity zones in the North Bay explains how to look up a parcel’s zone.

Step 6: Utilities

Ask each provider, in writing where possible, whether service is available and what it will cost to extend it: electric, water (public system or well), sewer (or septic), propane or gas, and internet. Distance to the nearest power line and the need for easements across neighboring land can change a budget substantially. In some rural areas a small water district or mutual water company serves a handful of parcels, so confirm who owns the system and whether new connections are being accepted.

Step 7: Williamson Act contracts

Many agricultural parcels in California carry a Williamson Act contract. According to the Department of Conservation, these contracts restrict land to agricultural or compatible open space use in exchange for lower property tax assessments. Participating counties and cities set their own rules on eligible uses and minimum acreage.

Source: Department of Conservation, Williamson Act Q&A. Ask the county for the contract itself and any local uniform rules, since these decide whether a home, ADU or other improvement is allowed.

Step 8: Financing land (lender practice)

Lender practice, not law: many buyers pay cash for land because fewer lenders make vacant land loans, and those that do commonly ask for a larger down payment and shorter term than a home loan. Local banks, credit unions, seller financing and construction-to-permanent loans are the usual alternatives. Terms vary widely, so talk with more than one lender early and make your offer contingent on financing if you need it.

Step 9: Title, survey and boundaries

Order the preliminary title report as soon as you are in contract and read every exception: easements, CC&Rs, mineral or water rights reservations, assessment liens and recorded agreements. A boundary survey confirms the lines, corners and any encroachments, and it shows whether improvements, fences or roads match the record. If the lender or title insurer will offer broader coverage based on a survey, ask what kind of survey it requires.

Land for sale in counties Diamond serves

Each county has its own planning, environmental health and fire rules. See current land listings and local notes for Sonoma County, Napa County, Marin County, Placer County and El Dorado County, or browse California agricultural land for sale.

Questions people ask

How do I know if a parcel in California is a legal lot?

Ask the city or county planning department. Under Government Code 66499.35, an owner or a buyer under contract can request a certificate of compliance, and a recorded final or parcel map serves as one for the parcels it describes.

Does having an APN mean I can build?

No. An assessor’s parcel number is for tax purposes. Buildability depends on legal-lot status, zoning, septic and water approvals, access and fire requirements.

What is a perc test and when is it done?

A percolation test measures how well soil absorbs wastewater, and it is part of the county’s septic site evaluation. In Sonoma County, sites with expansive clay soils require wet-weather testing, usually in the first quarter of the year.

Can I cancel a Williamson Act contract after I buy?

Only the landowner can apply, and it requires local government findings and a fee of 12.5%, per the Department of Conservation. Nonrenewal is the other route, but it takes 9 years for a standard contract to phase out.

Do fire safe regulations apply to my lot?

They apply to new construction in State Responsibility Areas and in Very High Fire Hazard Severity Zones within local responsibility areas. Ask the county fire marshal or local fire district what road, signing and water supply standards your project will need.

Can I get a mortgage for vacant land?

Some lenders make land loans, but terms are usually stricter than home loans. That is lender practice, not law, so compare offers from local banks and credit unions and consider seller financing.

What should my land purchase contingencies cover?

Time for zoning and legal-lot confirmation, septic and well testing, a survey, title review and any utility estimates. Match the contingency period to the county’s testing season.

Sources & notes

1. Government Code 65300 and 65860: general plan requirement and zoning consistency.
2. Government Code 66410 and 66499.35: Subdivision Map Act name; certificates of compliance.
3. State Water Resources Control Board: OWTS Policy.
4. Permit Sonoma: Septic site evaluations and Well and septic FAQ.
5. Public Resources Code 4290 and Board of Forestry, State Minimum Fire Safe Regulations fact sheet (Nov. 2022).
6. Department of Conservation: Williamson Act and Williamson Act Q&A.

Statute text was reviewed through a public mirror of the California codes; confirm current wording on leginfo.legislature.ca.gov. The fire safe regulations were amended after the 2022 fact sheet; ask the Board of Forestry or your local fire authority for the current standards. Financing comments describe common lender practice, not law.

General information, not legal, tax or lending advice. Updated November 2026. Primary sources are linked in this guide.

Related: California agricultural land for sale · Preliminary title reports · Buy with Diamond