Local zoning · Merced County

Merced County — Historic Preservation

Historic Preservation under the Merced County local zoning and planning code, with the controlling citations.

Last reviewed: July 6, 2026

Overview

This page explains how historic resources are addressed by the Merced County Zoning Code in the unincorporated areas. The Code provides an overlay tool called a Special Planning Zone (SPZ) that can be tailored as a Historic SPZ, and it routes projects on “sensitive sites” that include cultural or historic resources into design review. In limited cases, the County’s floodplain regulations recognize “historic structures” and allow narrowly tailored relief to preserve historic character. All standards here apply only in unincorporated Merced County (§ 18.02.030; see also the SPZ framework in § 18.18.010).

Key rule: If your project site contains known or listed cultural or historic resources, the County may require Site Plan and Design Review even when it otherwise wouldn’t (§ 18.122.020(C)(3)(f)).

How the Zoning Code handles historic resources

Applicability to unincorporated areas. The Zoning Code applies to all land use and development within the unincorporated area of the County (§ 18.02.030).
Special Planning Zone (SPZ) overlay. The County can adopt an overlay—by ordinance and zoning map amendment—specifically for historic purposes, identified as a “Historic SPZ.” An overlay SPZ adds to, and prevails over, base-zone rules (§ 18.18.010(B)–(C)).
Site Plan and Design Review for sensitive sites. Projects on sites with known, mapped, potentially significant, or listed cultural or historic resources can be deemed “sensitive” and required to obtain a Design Review Permit (§ 18.122.020(C)(3)(f)). The Director decides significance and sensitive-site status; determinations are appealable under § 18.144 (§ 18.122.020(B), (C)(2)).
Floodplain rules and “historic structure.” Within the floodplain chapter, “historic structure” is defined, and alterations that do not jeopardize historic designation are not treated as “substantial improvement.” Variances may be granted for repair/rehabilitation where necessary to preserve historic character, if all conditions are met (§ 18.26.030; § 18.26.060(C)(2)).
Review authority and process. Review authorities and permit types (including Site Plan and Design Review, Variances) are assigned in Table 6-1 (§ 18.112.020). Appeals run through § 18.144 (§§ 18.140.030–.060; § 18.122.020(B)).

Historic-related zoning districts and overlays (unincorporated areas)

Historic SPZ (Special Planning Zone) Overlay

Purpose. To protect unique historic resources and apply custom regulations beyond typical zoning. SPZs are created by ordinance with an exhibit map; an SPZ may be identified specifically as “Historic SPZ” (§ 18.18.010(B)).
Where it applies. Only where the Board has adopted a Historic SPZ on the Zoning Map; it functions as an overlay that prevails over the base zone when there’s a conflict (§ 18.18.010(C)).
Typical permitted uses. Not found in retrieved materials; each SPZ ordinance must specify uses and procedures (§ 18.18.010(B)).
Key dimensional standards. Not found in retrieved materials; each SPZ ordinance sets its own standards (§ 18.18.010(B)).
Practical note. Expect a custom rule-set (uses, development standards, review steps) embedded in the adopting ordinance. Coordinate early with Planning and confirm the overlay’s recorded map boundaries (§ 18.18.010(B)–(C)).

Castle Commerce Center and Airport SPZ — OS Open Space/Public Zone (historic context within Castle)

Purpose. Within the Castle SPZ, the OS Open Space/Public zone is intended to recognize and provide for open space, historic, and public land uses (e.g., parade grounds) (§ 18.18.020(B)(6)).
Where it applies. Only inside the Castle Commerce Center and Airport SPZ; locations correspond to the Castle Air Force Base Reuse Plan (§ 18.18.020(B)).
Typical permitted uses. Open space functions and related public and administrative uses; details are in the Castle SPZ land-use tables (§ 18.18.040(A)).
Key dimensional standards. Not found in retrieved materials; consult the Castle SPZ regulations and any referenced development standards (§ 18.18.040(A)).
Practical note. The Castle SPZ has a dedicated review path to keep projects aligned with the Reuse Plan (§ 18.18.030).

Decision-relevant rules at a glance

Mechanism	What triggers it	What it can require or allow	Who decides	Code Reference
Design Review for “sensitive sites”	Site contains known/mapped/potentially significant/listed cultural or historic resources	Site Plan and Design Review; objective conditions; appeal available	Director is initial decision-maker; appeal per § 18.144	§ 18.122.020(B), (C)(3)(f)
Historic SPZ overlay	Board adopts an SPZ identified as “Historic SPZ” on the Zoning Map	Custom permitted uses, procedures, and development standards that prevail over base zone	Legislative adoption; then project-level review per the adopting ordinance	§ 18.18.010(B)–(C)
Floodplain historic-structure relief	Project is repair/rehab of a “historic structure” in mapped flood hazard areas	Variance may be granted if it preserves historic designation and is minimum necessary	Board (variance) following Chapter 18.26 procedures	§ 18.26.030; § 18.26.060(C)(2)

Related considerations: Parking and similar site work that might otherwise be minor can still be pulled into design review if part of a sensitive site (§ 18.122.020(A)(3), (D)(3)). Coordinate with parking and development standards early to avoid redesign later.

Working with Site Plan and Design Review

Purpose and scope. Design Review ensures high-quality design and compatibility with neighborhood character (§ 18.122.010).
Triggers to watch. Relocations of buildings, exterior changes visible from the ROW, grading on steep slopes, and County projects can be “significant” and require Design Review; the Director decides, with appeal rights (§ 18.122.020(A), (B)).
Sensitive sites. The Director may require Design Review where a project is on a “sensitive site,” including those with cultural/historic resources (§ 18.122.020(C)(1), (3)(f)).

Interplay with other County rules

Variances and relief. Variances are quasi-judicial and follow assigned review authorities in Table 6-1 (§ 18.112.020). For floodplain cases, special variance findings apply, including for historic structures (§ 18.26.060(C)(2)). See variances and exceptions.
Signs on historic structures. Murals/signage that comply with sign rules are exempt from Design Review; verify how this interacts with any adopted Historic SPZ rules (§ 18.122.020(D)(11)). See signage.
Nonconforming situations. If an older structure’s status is nonconforming for other reasons, also consult nonconforming uses and confirm how any Historic SPZ overlay would interact (Not found in retrieved materials for a specific interaction rule).
Objective standards still apply. A Historic SPZ overlay, and design review outcomes, layer on top of base-zone rules in zoning and land use. SPZ rules, where in conflict, prevail (§ 18.18.010(C)).

State context you may bump into

Building code implications. While outside zoning scope, historic projects sometimes use the California Historical Building Code for flexibility; coordinate with the Building Division as needed. See California Building Standards Code. (Local zoning confirmation required; state CHBC reference provided for awareness only.)
ADUs near historic resources. State law allows local agencies to apply objective standards that prevent adverse impacts to resources listed on the California Register; ADUs remain allowed in historic districts so long as standards are objective. For context, see California ADU law (state guidance).

Information Gaps

County landmarking process. Not found in retrieved materials (e.g., no countywide register or landmark designation procedures).
Adopted Historic SPZs and their parcel maps/standards. Not found in retrieved materials; each SPZ is created by its own adopting ordinance (§ 18.18.010(B)). Verify with the jurisdiction.

Checklist

Confirm the site is in the unincorporated area (§ 18.02.030).
Check the Zoning Map for any Historic SPZ or other SPZ overlays and obtain the adopting ordinance with its specific standards (§ 18.18.010(B)–(C)).
Screen for “sensitive site” factors: any listed, mapped, or potentially significant cultural/historic resources (§ 18.122.020(C)(3)(f)).
If “sensitive,” scope a design review path and identify objective standards likely to apply (§ 18.122.010–.020).
If within flood hazard areas and a “historic structure,” evaluate whether variance-based relief is appropriate and document minimum-necessary preservation rationale (§ 18.26.030; § 18.26.060(C)(2)).
Coordinate base-zone rules with any overlay/SPZ provisions; where they conflict, the overlay prevails (§ 18.18.010(C)).
Align site elements (e.g., parking, access, landscaping) with development standards to avoid triggering redesign during design review (§ 18.122.010–.020).

Risks & Ambiguities

Issue	Why it matters	What to verify
No countywide landmark ordinance found	Without a formal local register, “historic structure” status typically depends on state/federal listings or program certification; this affects variance eligibility in flood areas	Whether the subject resource carries a qualifying designation; consult § 18.26.060(C)(2) and Article 8 Definitions referenced therein.
Historic SPZ details vary by ordinance	Each SPZ is customized; uses/standards/procedures aren’t in the base code	Obtain the adopting SPZ ordinance and map for the parcel (§ 18.18.010(B)–(C)).
Sensitive-site call is discretionary	Director’s significance/sensitivity determination controls design review routing and conditions	Early consultation; appeal window/standard under § 18.144 as cross-referenced in § 18.122.020(B), (C)(2).
Castle SPZ historic context is site-specific	Historic references apply to the Castle parade grounds; not a countywide rule	Confirm whether your parcel is in the Castle SPZ and the specific Castle zone (§ 18.18.020–.040).

Plain-English Summary

In unincorporated Merced County, the zoning code doesn’t set a single, countywide historic district. Instead, the County can adopt a Historic SPZ overlay for specific places, and it can require design review for projects on sites with cultural or historic resources. If you’re in a flood area and working on a qualifying historic structure, special variance provisions may help preserve the building’s character. Always check the Zoning Map for overlays, confirm whether your site is “sensitive,” and plan for design review if cultural/historic resources are present.

Source References

§ 18.02.030 Applicability to unincorporated area.
§ 18.18.010 SPZ purpose, adoption, and overlay precedence; Historic SPZ identification.
§ 18.18.020–.040 Castle SPZ purpose, zones, and review process (OS zone includes historic/public land uses).
§ 18.112.020 Review authority (Table 6-1).
§ 18.122.010–.020 Site Plan and Design Review; sensitive sites incl. cultural/historic resources; appeals under § 18.144.
§ 18.26.030; § 18.26.060(C)(2) Floodplain provisions; historic structure recognition and variance conditions.
State context (informational): California ADU Law guidance on historic resources (HCD).

Sources

Retrieved passages

Merced County Zoning Code Medium relevance
Merced County Zoning Code (§ 2) Medium relevance
Merced County Zoning Code (§ 2) Medium relevance
Merced County Zoning Code (§ 2) Medium relevance
Merced County Zoning Code (§ 65915) Medium relevance
Merced County Zoning Code (§ 2) Medium relevance
Merced County Zoning Code (§ 2) Medium relevance
Merced County Zoning Code (Section 18.26.050) Medium relevance
Merced County Zoning Code (§ 2) Medium relevance
Merced County Zoning Code (Article 7) Medium relevance
CBC § 2 (chapter which) Medium relevance
Merced County Zoning Code (chapter and) Medium relevance

Cited sections

Official Merced County code library

Frequently asked questions

Does Merced County have a countywide historic district in unincorporated areas?

No countywide historic district is established in the Zoning Code. Instead, the County can create a site-specific overlay called a Historic SPZ by ordinance and map adoption (§ 18.18.010(B)–(C)).

How do I know if my project near a historic resource needs design review?

If your site contains known, mapped, potentially significant, or listed cultural/historic resources, the Director may classify it as a “sensitive site,” which triggers Site Plan and Design Review (§ 18.122.020(C)(3)(f)). Determinations are appealable under § 18.144 (§ 18.122.020(B), (C)(2)).

What does a Historic SPZ regulate?

Each SPZ sets its own allowed uses, procedures, and development standards and is adopted by ordinance; where an SPZ conflicts with base zoning, the SPZ prevails (§ 18.18.010(B)–(C)). Obtain the parcel’s SPZ ordinance and map to know the rules.

Can a historic building in a flood hazard area get zoning relief to preserve its character?

Possibly. Floodplain regulations allow variances for repair/rehab of a “historic structure” when the work won’t jeopardize the historic designation and is the minimum necessary to preserve character (§ 18.26.060(C)(2)).

Does signage on a historic building require design review?

Murals/signage that comply with sign regulations are exempt from Design Review, but verify any stricter rules if a Historic SPZ applies (§ 18.122.020(D)(11)).

Who decides whether my project is “significant” enough to enter design review?

The Planning Director determines “significant projects” and “sensitive sites” for Design Review; you can appeal under § 18.144 (§ 18.122.020(B), (C)(2)).

Is there a special historic zone at Castle Commerce Center?

Within the Castle SPZ, the OS Open Space/Public zone recognizes “historic” and public land uses like the parade grounds, but it applies only inside Castle (§ 18.18.020(B)(6); § 18.18.040(A)).

Do the SPZ overlay rules replace my base zoning?

They can. If there’s a conflict, SPZ overlay provisions prevail over the base zone (§ 18.18.010(C)).

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