Sonoma County, CA zoning map, flood zone and property lines by address
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Towns in Sonoma County: Santa Rosa, Petaluma, Rohnert Park.
Flood zone by address
ParcelSheet reads FEMA's National Flood Hazard Layer at the lot: the zone, whether it is a high risk area where lenders ask for flood insurance, and the base flood elevation where FEMA lists one. FEMA's countywide study for Sonoma County has 259 FIRM panels, the newest effective July 2024; coastal V zones, where waves add to the flood, are mapped along its shore.
The official panel and any Letter of Map Amendment are at FEMA's Map Service Center. An elevation certificate for a Sonoma house comes from a licensed surveyor and is often on file with the county or city building office.
Property lines
The parcel outline, parcel number and mapped size come from the California county parcel layers (each county publishes its own), so a Sonoma lot shows the same lines the county assessor draws. Sonoma County covers about 1,008,216 acres of land and 122,883 acres of water.
Mapped lines are approximate. The Sonoma County assessor keeps the parcel record (Sonoma County website); a licensed surveyor sets the true corners.
Zoning
Sonoma County zones its unincorporated land, and Santa Rosa, Petaluma, Rohnert Park each zone the land inside their limits. ParcelSheet shows the use the county assessor lists for the lot and links the county planning department for the district, the uses it allows and the lot size it needs.
ADU and guest houses
Under California's Planning and Zoning Law (Government Code Title 7, Division 1, starting at section 65000), local governments can allow an accessory dwelling unit on a lot with a house. Whether a Sonoma lot can add one depends on its district; the county planning department has the rule. ParcelSheet shows the mapped lot size and the ground's slope, the first two things the question turns on.
Septic and soil
ParcelSheet reads the USDA soil survey at the lot: the soil's name, its septic absorption rating and whether it is prime farmland. Sonoma County is soil survey area CA097, Sonoma County, California, last updated September 2026, on Web Soil Survey.
A new or changed septic system in Sonoma County needs a permit from the Sonoma County environmental health department (under the State Water Resources Control Board OWTS Policy).
Setbacks
Setbacks in Sonoma County come from the zoning district: the front, side and rear distances a house must keep. ParcelSheet does not draw setback lines; the county zoning office gives them for the lot's district, and Santa Rosa, Petaluma, Rohnert Park for land inside their limits.
Hazards that apply
- Storm surge. Sonoma County has coastal V zones on its FEMA map, so storm surge reaches its shore. The county's evacuation zones are on its emergency management site; ParcelSheet shows the FEMA zone and the 3 ft sea level rise map at the lot.
- Wetlands and wildfire. ParcelSheet shows the National Wetlands Inventory near a Sonoma lot and the Forest Service wildfire hazard rating at it.
Questions
Is my house in a flood zone in Sonoma County?
Type the address in the box above and ParcelSheet reads FEMA's flood zone at the lot's center. FEMA's countywide flood map for Sonoma County has 259 panels, the newest effective July 2024. A lender or insurer uses the official FIRM panel; FEMA's Map Service Center has it.
How do I find property lines in Sonoma County?
Open the California map, type the address, and the parcel outline from the Sonoma County assessor shows on the map with its parcel number and mapped size. Mapped lines are approximate; only a licensed surveyor sets the true corners.
What is my property zoned in Sonoma County?
Zoning in Sonoma County is set by the county for unincorporated land and by each city (such as Santa Rosa, Petaluma) inside its own limits. ParcelSheet shows the use code the county assessor lists and links the office that sets the zoning; the planning office has the final word.
Can I build an ADU in Sonoma County?
Under California's Planning and Zoning Law (Government Code Title 7, Division 1, starting at section 65000), counties and cities can allow an accessory dwelling unit, and each sets its own rules. In Sonoma County ask the zoning office for the lot's district first; ParcelSheet shows the lot size as mapped so you can see the room you have.
Do I need a septic permit in Sonoma County?
Yes. A new or changed septic system in Sonoma County needs a permit from the Sonoma County environmental health department (under the State Water Resources Control Board OWTS Policy). ParcelSheet shows the USDA soil survey's septic rating at the lot, from survey area CA097 (Sonoma County, California).
What can I build on 5 acres in Sonoma County?
Zoning in Sonoma County is set by the county for unincorporated land and each city inside its own limits (such as Santa Rosa, Petaluma). The zoning district decides the uses, how many homes and the smallest lot it allows on 5 acres. ParcelSheet shows the lot size as mapped and the use code on the parcel record; the planning office has the district and its rules. See the Sonoma County website.
What are the residential setbacks in Sonoma County (2026)?
Setbacks in Sonoma County come from the zoning code of the county, or of the city when the lot is inside city limits: the front, side and rear distances depend on the lot's district. ParcelSheet does not draw setback lines or give a number it did not read; the zoning office gives them for the district. See the Sonoma County website.
Next to Sonoma County: Lake County, Marin County, Mendocino County, Napa County, Solano County.
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