Mariposa County — Overlay Districts

Last reviewed: July 6, 2026

Overview

In unincorporated areas of Mariposa County, “combining” or overlay districts sit on top of a principal zoning district and modify what you can do on the land, how projects are reviewed, and in some cases, basic dimensional limits. The County’s overlay lineup includes the OWO, APO, SHO, DRO, HDRO, REO‑1, REO‑2, and (for Greeley Hill) the BDO; a parcel can carry one or more overlays in addition to its base zone, and overlay rules supersede where more restrictive. See the County’s list of established combining districts in § 17.04.030 , and how they modify principal zones in § 17.04.030(3) . Official boundaries appear on the County’s zoning maps in § 17.04.035 .

Plain English: An overlay modifies your base zoning; if the overlay is stricter than the base zone, the stricter overlay rule controls in unincorporated areas.

Before digging into an overlay, always cross-check your principal zone in Mariposa County Zoning and the countywide Development Standards.

What overlays exist in unincorporated Mariposa County?

Per § 17.04.030, the County recognizes:

• OWO — Open Watershed Overlay
• APO — Airport Overlay
• SHO — Scenic Highway Overlay
• DRO — Design Review Overlay
• HDRO — Historic Design Review Overlay
• REO‑1 — Residential Exclusive Overlay One
• REO‑2 — Residential Exclusive Overlay Two
• BDO — Business District Overlay (Greeley Hill) appears as Chapter 17.82 in Title 17’s table of contents and applies to the Greeley Hill Town Planning Area core (see §§ 17.82.010–.030) .

The code also lists “TE Timber Exclusive” as a combining district in § 17.04.030; however, the timber classification is implemented as a principal zone (TEZ) at § 17.44 in Title 17’s contents. Overlay-specific TE standards were not located in the retrieved materials (Not found in retrieved materials).

District-by-District Details

Open Watershed Overlay (OWO)

• Purpose and where it applies: Applied to lands used or proposed as surface water supply watersheds, modifying base zoning to protect water quality; shown on the zoning map per § 17.60.010 .
• Typical permitted uses: Single-family residences, home enterprise, agriculture, public parks, and managed timber production; no conditional uses listed; all others prohibited per § 17.60.010(1) .
• Key dimensional standards: Minimum parcel size is typically 20 acres (or larger if the principal zone requires it); density is the more restrictive of the principal zone or 1 dwelling per 20 acres per § 17.60.010(1)(2)–(3) .
• Special development/procedural standards: Designated “erosion hazard areas”; approved percolation tests required; septic must be on an approved tested location per § 17.60.010(2) . Boundaries may be amended when watershed lines are surveyed per § 17.60.010(3) .

Airport Overlay (APO)

• Purpose and where it applies: Regulates land uses within County airport influence areas to prevent airport hazards; modifies principal zones per § 17.64.010 .
• Typical permitted uses: On airport property, additional aviation-related uses (hangars, fueling, runways, terminals) per § 17.64.010(1)(1) .
• Key dimensional standards: Height limits tied to FAA imaginary surfaces, often capped at 35 ft; more restrictive height applies where multiple surfaces overlap per § 17.64.010(5)–(7) .
• Special development/procedural standards:
  • Use controls by subzone: In Zone A, no structures; in Zone B, no flammable-material industries or high-assembly uses over 50 persons/acre; clustering encouraged; in Zone C, cluster residential/public assembly away from heavy flight paths per § 17.64.010(1)(3) .
  • Noise: New or majorly renovated housing in future 60–65 CNEL must provide analysis/insulation to meet indoor <45 CNEL per § 17.64.010(8) .
  • ALUC review: Plan/ordinance amendments within the airport influence area must be submitted to the Airport Land Use Commission per § 17.64.010(9) .

Scenic Highway Overlay (SHO)

• Purpose and where it applies: Protects scenic quality along State- or Board-designated scenic highways; combined with any principal zone per § 17.65.010 .
• Required review: A Scenic Highway Review Plan is required for any commercial, industrial, multi-family, or single-family use (including home enterprises), unless the applicant demonstrates the project is not visible from the scenic highway per § 17.65.010(1) . Planning Director decides within 30 days for complete applications per § 17.65.010(3) .
• Uses:
  • Same as principal zone, with exceptions: commercial timber harvesting is allowed subject to State special treatment standards; several rural industrial/outdoor uses become conditional; off-site signs are prohibited per § 17.65.010(4) .
• Key dimensional/design standards: Base-zone standards govern setbacks/height/parking unless the SHO has stricter standards; for multi-family, commercial and industrial projects, additional site design standards apply per § 17.65.010(4)–(5) .
• Nonconforming rules: Expansion and rebuilds are allowed only with scenic highway review; 12-month discontinuance affects re-establishment per § 17.65.010(7) .

Design Review Overlay (DRO)

• Purpose and where it applies: Protects the visual character of designated districts with unique architecture/scenic qualities; combined with any zone per § 17.66.010(A) .
• Uses and base standards: Uses, density, setbacks, building height, parking follow the principal zone unless a DRO special standard is adopted; Board of Supervisors adopts area-specific architectural themes/guidelines per § 17.66.010(A), (G) .
• Required review: A Design Review Plan is required for commercial, industrial, and multi-family uses; small-scale projects (<5,000 sq ft) or minor alterations that clearly meet adopted standards may be exempted from committee review; emergency shelters are exempt from DRO application review per § 17.66.010(C), (F) .
• Process: Submittal content, committee recommendation, and Planning Director action windows are in § 17.66.010(D)–(E) . See also Mariposa County Design Review.

Historic Design Review Overlay (HDRO)

• Purpose and where it applies: Preserves historic districts by regulating design of new work and alterations; can be combined with any zone, often used in the Mariposa Town Planning Area per § 17.67.010 .
• Uses/base standards: Same as principal zone; where HDRO special standards conflict, the HDRO standard prevails per § 17.67.010(1)–(2) .
• Required review: A Design Review Plan is required before commercial, industrial or residential development, exterior signs, or grading/building permits are issued in HDRO areas per § 17.67.010(3) .
• Demolition in HDRO: Demolition of identified historic resources in an HDRO or the Mariposa Town Planning Area requires Planning Director approval, with strict findings; limited stays of demolition may be used to seek alternatives per § 17.67.020 . See also Mariposa County Historic Preservation and Mariposa County Signage.

Residential Exclusive Overlay One (REO‑1)

• Purpose and where it applies: Limits land to exclusively single-family residential use; may be requested at subdivision or by contiguous owners per § 17.68.010 .
• Uses: Only residential uses, keeping of domestic animals, accessory buildings/structures, and utility transmission/distribution; agriculture and all other uses are prohibited per § 17.68.010(1) .
• Dimensional standards: Lot size and density as in the principal zone per § 17.68.010(3)–(4) .

Residential Exclusive Overlay Two (REO‑2)

• Purpose and where it applies: Similar to REO‑1 but also allows limited personal service businesses when residents are the only employees per § 17.72.010 .
• Uses: Residential/domestic animals/accessory/utility uses, plus resident-only personal services; no conditional uses; agriculture and others prohibited per § 17.72.010(1) .
• Dimensional standards: Lot size and density follow the principal zone per § 17.72.010 .

Business District Overlay — Greeley Hill (BDO‑GH)

• Purpose and where it applies: Creates a commercial/light industrial core within the Greeley Hill Town Planning Area; combined with the TPA district per § 17.82.010 .
• Uses: Same as the principal zone; indoor self-service storage may be allowed through a “Use Permit Determination” process; service stations (with car wash/auto repair) and bulk propane satellite-storage are conditional uses per § 17.82.020(1)–(2) .
• Key development standards: Special landscaping and lighting standards for self-service storage (screening, indigenous/water-conserving plantings, fully shielded fixtures) per § 17.82.020(6) and related standards . Minimum setbacks are “as established by the principal zone” per § 17.82.020(2)–(5); additional setback criteria appear elsewhere in Title 17 for adjacent residential contexts.

Quick-Use Table: What changes in each overlay?

Tip: When an overlay references parking, signage, landscaping, or other development controls, check the countywide Parking, Signage, and Landscaping and Screening pages. For discretionary relief, see Mariposa County Variances and Exceptions. Nonconforming situations in an overlay must follow the County’s general rules; SHO includes overlay-specific nonconforming provisions in § 17.65.010(7), while general rules are on Mariposa County Nonconforming Uses.

Checklist

• Confirm your parcel’s principal zone and any overlays on the official zoning maps (unincorporated areas only) per § 17.04.035 .
• If in OWO, plan for percolation testing and septic placement on a tested location; verify minimum 20-acre standards or stricter principal-zone standards per § 17.60.010 .
• If in APO, check which APO subzone (A/B/C) you’re in; verify height limits and whether a noise analysis is needed for new/majorly renovated housing per § 17.64.010 .
• If in SHO, determine visibility from the scenic corridor; prepare a Scenic Highway Review Plan unless you can document non-visibility per § 17.65.010 .
• If in DRO or HDRO, budget time for Design Review Plan submittal, guidelines, and committee/Director review per §§ 17.66.010, 17.67.010 .
• If proposing demolition within HDRO or identified historic sites, seek demolition approval with required findings per § 17.67.020 .
• If in REO‑1 or REO‑2, ensure your use list fits the overlay (agriculture is prohibited; REO‑2 allows resident-only personal services) per §§ 17.68.010, 17.72.010 .
• If in BDO‑GH, apply applicable use-permit determinations and self‑storage landscaping/lighting standards per § 17.82.020 .
• Coordinate any overlay-driven design requirements with Design Review and base Development Standards.

Risks & Ambiguities

Plain-English Summary

Overlays are add-ons to your base zoning. In unincorporated Mariposa County they can require extra review (scenic or design review), restrict heights and uses near airports, lock an area to residential-only, or add screening rules in Greeley Hill. Start by confirming your overlays on the County zoning map, then follow the overlay’s special procedures and standards—when overlay rules are stricter than base zoning, the overlay wins. Verify with the jurisdiction for parcel-specific questions.

Source References

• § 17.04.030 Establishment of zoning districts; combining/overlay districts; effect of overlays on principal zones; mapping in § 17.04.035
• § 17.60.010 Open Watershed Overlay (OWO) — uses, parcel size/density, improvement and amendment standards
• § 17.64.010 Airport Overlay (APO) — uses, subzones A/B/C, height, CNEL, ALUC submittals
• § 17.65.010 Scenic Highway Overlay (SHO) — plan requirement, exemptions, use controls, nonconforming provisions
• § 17.66.010 Design Review Overlay (DRO) — purpose, required review, exemptions, process, themes/guidelines
• §§ 17.67.010–.020 Historic Design Review Overlay (HDRO) — procedures, design review, demolition controls
• § 17.68.010 Residential Exclusive Overlay One (REO‑1) — permitted/prohibited uses; implementation; density/lot size
• § 17.72.010 Residential Exclusive Overlay Two (REO‑2) — uses incl. resident-only personal services; implementation; density/lot size
• §§ 17.82.010–.020 Business District Overlay, Greeley Hill (BDO‑GH) — purpose; uses; conditional uses; storage facility standards
• Title 17 table of contents confirming overlay chapters (APO, SHO, DRO, HDRO, REO‑1/‑2, BDO; TEZ as principal zone)

Retrieved passages

• Mariposa County Zoning Code (section 17.64.010.A) High relevance show source text
• Mariposa County Zoning Code (section by) High relevance show source text
• Mariposa County Zoning Code (Chapter 17.108.) High relevance show source text
• Mariposa County Zoning Code (section conflicts) High relevance show source text
• Mariposa County Zoning Code (Chapter 17.08) High relevance show source text
• CFC § 17.67.010 (section no) High relevance show source text
• Mariposa County Zoning Code Medium relevance show source text
• Mariposa County Zoning Code (title is) Medium relevance show source text
• Mariposa County Zoning Code (section shall) High relevance show source text
• Mariposa County Zoning Code (section 17.66.010) High relevance show source text
• Mariposa County Zoning Code (section 17.108.130) High relevance show source text
• Mariposa County Zoning Code (section 17.108.200) High relevance show source text
• Mariposa County Zoning Code (section 17.65.010) High relevance show source text
• Mariposa County Zoning Code (section 17.108.050.) Medium relevance show source text
• Mariposa County Zoning Code (section in) Medium relevance show source text

Cited sections

• § 17.04.030 Establishment of zoning districts; combining/overlay districts; effect of overlays on principal zones; mapping in § 17.04.035 (§ 17.04.030)
• § 17.60.010 Open Watershed Overlay (OWO) — uses, parcel size/density, improvement and amendment standards (§ 17.60.010)
• § 17.64.010 Airport Overlay (APO) — uses, subzones A/B/C, height, CNEL, ALUC submittals (§ 17.64.010)
• § 17.65.010 Scenic Highway Overlay (SHO) — plan requirement, exemptions, use controls, nonconforming provisions (§ 17.65.010)
• § 17.66.010 Design Review Overlay (DRO) — purpose, required review, exemptions, process, themes/guidelines (§ 17.66.010)
• §§ 17.67.010–.020 Historic Design Review Overlay (HDRO) — procedures, design review, demolition controls (§ 17.67.010)
• § 17.68.010 Residential Exclusive Overlay One (REO‑1) — permitted/prohibited uses; implementation; density/lot size (§ 17.68.010)
• § 17.72.010 Residential Exclusive Overlay Two (REO‑2) — uses incl. resident-only personal services; implementation; density/lot size (§ 17.72.010)
• §§ 17.82.010–.020 Business District Overlay, Greeley Hill (BDO‑GH) — purpose; uses; conditional uses; storage facility standards (§ 17.82.010)
• Title 17 table of contents confirming overlay chapters (APO, SHO, DRO, HDRO, REO‑1/‑2, BDO; TEZ as principal zone) (Title 17)
• MariposaCounty_ZoningCode.md

• Official Mariposa County code library