Reference

Glossary

Name: Brian Zuckerman — W Real Estate
Address: 243 Healdsburg Ave, Healdsburg, CA, 95448, US
Telephone: (760) 699-1258
Price range: $$$$

Plain-language definitions of the real estate, tax, insurance, and rural-property terms used across this site. Linked inline from the relevant articles — come back here whenever a term needs a quick refresher.

Ad valorem: Latin for 'according to value.' A tax calculated as a percentage of the assessed value of the property. California's basic property tax is an ad valorem tax, capped under Proposition 13 at 1 percent of assessed value before local additions.
ADU (Accessory Dwelling Unit): A secondary residential unit on a parcel that already has a primary residence. California law has progressively expanded ADU rights and reduced permitting friction, making them a common value-add improvement on Sonoma County properties.
Base-year value: Under Proposition 13, the assessed value of a property at acquisition or new construction. The base-year value increases by no more than 2 percent annually unless a triggering event (sale, major construction) causes reassessment to current market value.
Cal Fire State Responsibility Area (SRA): Areas of California where Cal Fire has primary responsibility for wildfire prevention and suppression, generally non-urban land outside city boundaries. SRA designation, along with fire-hazard severity zoning, affects insurance availability and pricing.
CFD (Community Facilities District): A special tax district created under California's 1982 Mello-Roos Community Facilities Act to fund infrastructure for new development. Bonds are repaid through annual special taxes assessed on parcels in the district. CFD charges are separate from the ad valorem rate and not capped by Prop 13.
Defensible space: A managed buffer zone of cleared and reduced-fuel vegetation around structures in fire-prone areas. California Public Resources Code §4291 requires defensible space for properties in fire zones. Common guidance: 30-foot inner zone (lean, clean, and green) and 30 to 100 feet of reduced fuel load beyond that.
Difference-in-conditions (DIC) policy: A wrap-around insurance policy paired with FAIR Plan dwelling coverage to provide the protections FAIR Plan does not — typically liability, theft, water damage, and contents. Combined FAIR Plan plus DIC has become a common structure for high-fire-risk Sonoma County properties.
FAIR Plan: The California Fair Access to Insurance Requirements Plan. The state's insurer of last resort for property owners unable to obtain coverage in the standard admitted market, typically due to wildfire risk. Provides dwelling fire coverage only.
Mello-Roos: Common shorthand for special taxes assessed under a Community Facilities District (CFD) created under California's 1982 Mello-Roos Community Facilities Act. Funds infrastructure for new development. Visible as a separate line item on the property tax bill.
NEM 3.0: California's third Net Energy Metering tariff for solar customers, effective April 2023. NEM 3.0 reduced the credit utilities pay for exported solar power compared to prior versions, which has shifted the economics of residential solar toward larger systems with batteries and on-site consumption.
Perc test (percolation test): A site evaluation that measures how quickly soil absorbs water. Required to design and permit a conventional septic system. Sites with poor percolation (clay soils, high water tables) may require an engineered alternative system at significantly higher cost.
Proposition 13: 1978 California ballot initiative that capped the base property tax rate at 1 percent of assessed value, limited annual assessment increases to 2 percent, and triggered reassessment to market value only on a change of ownership or new construction.
Proposition 19: 2020 ballot initiative effective April 1, 2021. Allows homeowners aged 55 or older — or severely disabled, or victims of a wildfire or other declared disaster — to transfer the assessed value of their existing primary residence to a replacement primary residence anywhere in California, up to three times in a lifetime. Filed via BOE Form 19-B.
PSPS (Public Safety Power Shutoff): Preemptive power outages by PG&E during high fire-weather conditions, intended to prevent equipment-caused wildfires. PSPS events are a permanent feature of rural Sonoma County life and a primary reason owners install whole-home generators or solar-plus-battery systems.
Septic system: An on-site wastewater treatment system used in lieu of municipal sewer service. A standard gravity system flows into a tank and then a leach field; alternative systems (mound, sand filter, advanced treatment) are used on parcels with poor soil conditions or shallow groundwater.
STR (Short-Term Rental): A residential property rented for periods generally under 30 days, marketed through platforms like Airbnb and VRBO. Sonoma County and its incorporated cities maintain separate STR ordinances with permit requirements, caps, and operating restrictions that vary by jurisdiction.
Surplus lines insurance: Coverage written by non-admitted carriers — insurers not licensed in California — for risks the standard admitted market will not write. Common for high-value or high-fire-risk Sonoma County properties needing coverage above FAIR Plan limits.
Well log: A document recording the depth, geology, casing, and initial yield of a drilled well. Filed with the California Department of Water Resources. A well log plus recent flow-rate data are essential due-diligence documents on any rural property purchase.
Williamson Act: The California Land Conservation Act of 1965. A 10-year rolling contract between a landowner and the county in which the parcel is restricted to agricultural or open-space use in exchange for property tax assessment based on agricultural productivity rather than market value, dramatically reducing the tax bill. A 20-year Farmland Security Zone variant also exists.

Term you don't see here? Let me know and I'll add it.