Mendocino County — Overlay Districts

Last reviewed: July 6, 2026

Overview

In unincorporated Mendocino County, “overlay districts” are codified as Combining Districts that sit on top of a base zoning district and add extra use rules or development standards. When a combining district applies, its rules control over the underlying zone; if multiple overlays overlap, the most stringent standard governs unless the code says otherwise, and all overlay boundaries are shown on County zoning maps and written descriptions. See § 20.040.010, § 20.040.015, and § 20.040.020 . This page focuses only on what the County zoning ordinance says about overlays in unincorporated areas and how they work alongside base Mendocino County Zoning, Land Use, and Development Standards.

Plain-English rule of thumb: an overlay district adds to (and can be stricter than) the base zone; if two overlays stack, follow the strictest rule unless the code expressly says otherwise per § 20.040.010 .

How overlay districts are established and mapped

• The County lists the inland Combining Districts (overlay designators) as: AZ, C, CA, CC, CP, FP, IS, L, MP, PD, P, R, SS in § 20.040.010 .
• District boundaries are by written description, APNs, and County zoning maps adopted under Chapter 20.212. The County maintains an adopted “Computer Print Out of Zoning Designation by Assessors Parcel Number” as part of the official record (§ 20.040.015–.020) .
• Where a boundary is unclear, the Planning and Building Services Director makes the call subject to appeal, using the rules in § 20.040.025 .

If your site is in the Coastal Zone (including the unincorporated Town of Mendocino), the Coastal Zoning Code chapters apply; certain combining districts are unique there, and the certified Town code supersedes general County zoning within its mapped boundary (§ 20.604.020) . Town combining districts and their boundaries are established in § 20.640.010 and § 20.640.015 .

Core Combining Districts in unincorporated inland areas (Title 20)

Below are the inland overlay districts named in § 20.040.010, with their purpose, effect, key standards, and where they apply. When an overlay is present, also check related processes like Design Review, Parking, Signage, Landscaping and Screening, and potential Variances and Exceptions the project may still require.

“CA” Cannabis Accommodation Combining District

• Purpose/effect: Accommodate existing commercial cannabis cultivation with tailored standards that override base-zone standards where they conflict (§ 20.118.010, § 20.118.020(C)) .
• Where it applies: Areas with existing commercial cultivation; zone where most lots allow residential by right; at least 10 contiguous legal parcels; established by petition showing support from >60% of affected owners or other approved method (§ 20.118.020(A)–(B), § 20.118.030(B)) .
• Key standards:
  • Application window for cultivation permits in a newly adopted CA area: 180 days from the effective date (§ 20.118.040(A)) .
  • Sunset provision does not apply in CA (§ 20.118.040(B)) .
  • Allowed permit types for existing sites: Small Outdoor, Small Indoor (Artificial Light), Small Mixed Light per cross-references (§ 20.118.040(C)) .
  • Setbacks for cultivation may be reduced: to property line minimum 20 ft, and to an occupied residence on another parcel 20 ft, with potential further reductions by Administrative Permit (§ 20.118.040(D)–(F)) .
  • Rezoning the underlying parcels does not change CA overlay permissions (§ 20.118.040(G)) .
  • Changes to or repeal of a CA overlay are restricted for 10 years; owner-driven amendments need support thresholds; limited 3-year continuance for nonconforming cultivators if a CA is repealed (§ 20.118.050, § 20.118.060) .
• Adopted CA areas include: Covelo Core, Covelo Fairbanks Road, Laytonville, South Leggett (§ 20.118.070) .

“CP” Commercial Cannabis Prohibition Combining District

• Purpose/effect: Prohibits all new and unpermitted cannabis cultivation (with limited exemptions) and all cannabis facilities within the overlay (§ 20.119.010, § 20.119.040(A)) .
• Where it applies: Areas where a majority of parcels allow residential by right; 10+ contiguous legal parcels; established by owner petition demonstrating >60% support or other County-approved method (§ 20.119.020(A)–(B), § 20.119.030(B)) .
• Conflict rule: CP standards prevail over base-zone standards (§ 20.119.020(C)) .

“MP” Mineral Processing Combining District

• Purpose/effect: Allows limited on-site processing of mineral resources (asphalt and/or concrete batch plants) as an overlay; requires a major use permit (§ 20.134.005, § 20.134.010(A)) .
• Where it applies: Only to R-L (Range Lands) zoned areas within 0.5 miles of a legally established, active mining operation; may not be in a FEMA flood hazard area or under a Williamson Act contract (§ 20.134.010(B)) .
• Key standards:
  • Equipment height: batch plant equipment subject to 75 ft height cap instead of base R-L height (§ 20.134.010(D)(2)) .
  • Processing must cease within 1 year after mining ends; reclamation required under an approved plan (§ 20.134.010(D)(3)–(4), § 20.134.015) .

“L” Special Minimum Lot Size Combining District (inland)

• Purpose/effect: Sets a larger minimum lot size than the base zone to match General Plan density or protect resources (e.g., AG:L-80) (§ 20.132.005) .
• Key standard: The “L” minimum replaces the base-zone minimum (§ 20.132.010) .
• Where it applies: As mapped or described by the County (§ 20.040.015–.020) .

“AZ” Airport Zone Combining District

• Purpose/effect: Not found in retrieved materials. Listed among established inland overlays (§ 20.040.010). Verify mapped locations and standards with the County .
• Key standards: Not found in retrieved materials.

“C” Cluster Combining District

• Purpose/effect: Not found in retrieved materials for inland areas. The Coastal code shows a related clustering concept with fee waivers in certain cases (§ 20.412.030), but the inland “C” standards were not retrieved. Verify with the jurisdiction .
• Key standards: Not found in retrieved materials.

“CC” Community Character Combining District

• Purpose/effect: Not found in retrieved materials. Verify with the jurisdiction (§ 20.040.010 reference only) .

“FP” Special Flood Plain Combining District (inland)

• Purpose/effect: Not found in retrieved materials for inland chapters; coastal floodplain regulation is addressed separately below. The inland FP overlay is listed in § 20.040.010 but no standards were retrieved; verify with the jurisdiction .

“IS” Isolated Service Combining District

• Purpose/effect: Not found in retrieved materials. Verify with the jurisdiction (§ 20.040.010 reference only) .

“PD” Planned Development Combining District (inland)

• Purpose/effect: Not found in retrieved materials for inland Title 20. A PD tool exists in the Mendocino Town (coastal) code; see coastal section below. Verify inland PD standards with the jurisdiction (§ 20.040.010 reference only) .

“P” Plan Combining District

• Purpose/effect: Not found in retrieved materials. Verify with the jurisdiction (§ 20.040.010 reference only) .

“R” Commercial Resort Combining District

• Purpose/effect: Not found in retrieved materials. Verify with the jurisdiction (§ 20.040.010 reference only) .

“SS” Seismic Study Combining District

• Purpose/effect: Not found in retrieved materials. Verify with the jurisdiction (§ 20.040.010 reference only) .

Coastal Zone and Town of Mendocino Combining Districts (unincorporated coastal areas)

If your parcel lies in the Coastal Zone, the coastal chapters govern. For the unincorporated Town of Mendocino, the Town Zoning Code supersedes general County zoning and includes its own combining districts and maps (§ 20.604.020, § 20.640.010–.015) .

“DL” Development Limitations Combining District (coastal)

• Purpose/effect: Applied to parcels or portions of parcels with serious development constraints (e.g., >30% slopes, landslide potential, geophysical hazards) (§ 20.416.005) .
• Additional requirements: Development in DL must also comply with floodplain and hazard/resource protections in § 20.420 and §§ 20.488–20.500 (§ 20.416.015) .

Coastal Floodplain Requirements

• Rule: Within the Coastal Zone, the County’s Floodplain Ordinance (Chapter 22.17) governs floodplain standards; the coastal chapter formally incorporates it (§ 20.420.005) .

“L” Special Minimum Lot Size Combining District (coastal)

• Purpose/effect: Mirrors inland “L” by setting larger minimum parcel sizes to align zoning with General Plan density or constraints (§ 20.424.005) .
• Regulations: See § 20.424.010 (content not included in retrieved excerpt) — verify project-specific application with the County .

Mendocino Visitor Serving Facilities Combining District — “*” and “*B” (Town of Mendocino)

• Purpose/effect: Reserves mapped sites for visitor accommodations within the Mendocino Town Plan area: “*” for hotels/inns (5+ units), and “*B” for bed-and-breakfasts (≤4 rooms), as listed in Appendix 2 of the Town Plan (§ 20.684.005) .
• Permitted in overlay: Visitor accommodations consistent with the map designation; the base zone’s principal permitted use still applies (§ 20.684.010) .
• Notes: Some residential districts in town reference the *B overlay for B&B allowance (e.g., § 20.644.005) .

Mendocino PD — Planned Unit Development (Town of Mendocino)

• Existence/designator: “PD” is a Town combining district listed in § 20.640.010; see mapped boundaries in § 20.640.015 .
• Standards: Not found in retrieved materials. A snippet referencing PD modifications was retrieved without a specific section number; verify standards with the jurisdiction. Not found in retrieved materials for an inland PD chapter citation.

At‑a‑glance: key overlay effects that change decisions

Tip: overlays can also affect whether Nonconforming Uses are created or expanded if your use predates an overlay change, and whether you may seek relief under Variances and Exceptions.

Checklist

• Confirm your parcel is in unincorporated Mendocino County and identify all mapped combining districts (overlay designators) on the official County zoning maps and APN listing (§ 20.040.015–.020) .
• Determine whether the site is in the Coastal Zone or the unincorporated Town of Mendocino; if so, use the coastal/Town chapters and maps (§ 20.604.020; § 20.640.015) .
• If in a CA or CP overlay, verify eligibility, petition thresholds, and timing; for CA, note the 180‑day permit window and reduced setbacks, and that CA rights persist despite later rezones (§ 20.118.030–.040, .050–.070; § 20.119.020–.040) .
• If MP applies, confirm R‑L zoning, the 0.5‑mile mining proximity, floodplain/Williamson Act exclusions, and prepare a Reclamation Plan with your use permit (§ 20.134.010–.015) .
• If “L” applies, size lots to the overlay minimum rather than the base zone (§ 20.132.010; see also coastal § 20.424.005–.010) .
• If in “DL” or mapped coastal floodplain/hazard areas, budget for geologic/flood studies and compliance with hazard/resource protections (§ 20.416.015; § 20.420.005; §§ 20.488–20.500) .
• Layer in any process-specific requirements such as Design Review, Parking, and site Landscaping and Screening where applicable.

Risks & Ambiguities

Information Gaps

• Inland standards for the AZ, C, CC, FP (inland chapter), IS, PD (inland), P, R, and SS combining districts were not found in the retrieved materials. Not found in retrieved materials. Verify with the jurisdiction (see § 20.040.010 list) .
• Detailed coastal text for L (coastal) § 20.424.010 was not included in the excerpts. Not found in retrieved materials.
• Town of Mendocino PD combining district implementation standards were not shown beyond the designator listing. Not found in retrieved materials.

Plain-English Summary

In unincorporated Mendocino County, overlay (combining) districts add extra rules on top of your base zoning. Some are very targeted—like the CA overlay that relaxes certain cannabis‑site setbacks, the CP overlay that bans commercial cannabis, the MP overlay that allows batch plants near active mines, the L overlay that increases minimum lot sizes, and coastal tools like DL, coastal floodplain integration, and Town of Mendocino’s visitor‑serving “*/*B” sites. Start by checking your parcel’s overlay designators on the County maps, then design to the strictest applicable rule and confirm any coastal/Town‑specific layers.

Source References

• § 20.040.010 (Combining Districts established); § 20.040.015–.020 (maps/locations); § 20.040.025 (uncertain boundaries)
• § 20.118.010–.070 (“CA” Cannabis Accommodation Combining District)
• § 20.119.010–.040 (“CP” Commercial Cannabis Prohibition Combining District)
• § 20.134.005–.015 (“MP” Mineral Processing Combining District)
• § 20.132.005–.010 (“L” Special Minimum Lot Size — inland)
• § 20.416.005–.015 (“DL” Development Limitations — coastal)
• § 20.420.005 (Coastal Floodplain Ordinance incorporation)
• § 20.424.005–.010 (“L” Special Minimum Lot Size — coastal)
• § 20.684.005–.015 (Mendocino Visitor Serving Facilities Combining District)
• § 20.604.020; § 20.640.010–.015 (Town of Mendocino applicability and combining districts)

Retrieved passages

• Mendocino County Zoning Code (§ 32) High relevance show source text
• Mendocino County Zoning Code (§ 8) High relevance show source text
• Mendocino County Zoning Code (CHAPTER 20.407A) High relevance show source text
• Mendocino County Zoning Code (§ 35) High relevance show source text
• Mendocino County Zoning Code (Chapter 20.684) High relevance show source text
• Mendocino County Zoning Code (section 20.242.070) Medium relevance show source text
• Mendocino County Zoning Code (section 10A.17.040) Medium relevance show source text
• Mendocino County Zoning Code (§ 2) Medium relevance show source text

Cited sections

• § 20.040.010 (Combining Districts established); § 20.040.015–.020 (maps/locations); § 20.040.025 (uncertain boundaries) (§ 20.040.010)
• § 20.118.010–.070 (“CA” Cannabis Accommodation Combining District) (§ 20.118.010)
• § 20.119.010–.040 (“CP” Commercial Cannabis Prohibition Combining District) (§ 20.119.010)
• § 20.134.005–.015 (“MP” Mineral Processing Combining District) (§ 20.134.005)
• § 20.132.005–.010 (“L” Special Minimum Lot Size — inland) (§ 20.132.005)
• § 20.416.005–.015 (“DL” Development Limitations — coastal) (§ 20.416.005)
• § 20.420.005 (Coastal Floodplain Ordinance incorporation) (§ 20.420.005)
• § 20.424.005–.010 (“L” Special Minimum Lot Size — coastal) (§ 20.424.005)
• § 20.684.005–.015 (Mendocino Visitor Serving Facilities Combining District) (§ 20.684.005)
• § 20.604.020; § 20.640.010–.015 (Town of Mendocino applicability and combining districts) (§ 20.604.020)
• MendocinoCounty_ZoningCode.md

• Official Mendocino County code library