Local zoning · Imperial County

Imperial County — Historic Preservation

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

Last reviewed: July 6, 2026

Overview

This page explains how historic preservation is treated under the Imperial County Codified Ordinances for unincorporated areas. The County’s zoning framework in Title 9 focuses on base zones and overlays; there is no dedicated “Historic Preservation” zoning district, and the ordinance addresses historic resources primarily through floodplain rules and state-law triggers. For general context on how zoning works in unincorporated areas, see the Imperial County zoning & planning overview and Imperial County Zoning.

Key takeaway: Imperial County’s zoning ordinance does not establish a local historic district or overlay; instead, preservation-related rules appear where a property is a “historic structure” in flood hazard areas or when state-law programs (like SB 9 urban lot splits) exclude historic resources. See § 91401.07, § 91606.01, and § 90813.06.

How the ordinance addresses “historic”

The County defines an “historic structure” for floodplain management purposes to include properties listed in or contributing to the National Register, the California Office of Historic Preservation’s inventory, or a certified local inventory/program. See § 91401.07.
In flood hazard areas, variances may be issued for the repair or rehabilitation of an historic structure if the work does not preclude its continued designation and the variance is the minimum necessary to preserve historic character. See § 91606.01(A).
For SB 9–style urban lot splits, a parcel is disqualified if it is within a historic district or is a property included on the State Historic Resources Inventory. See § 90813.06.

Where historic rules intersect the zoning map

Imperial County’s zoning system establishes base zones (e.g., R-1, C-1, A-2) and overlays in Title 9, Division 5. Base zones are listed in § 90501.02, and overlays are established in § 90501.03. Official zoning maps control where overlays apply; only sealed maps issued by the Planning Department are the official record per § 90501.04.

Base zones: R-1, R-2, R-3, R-4 (residential); A-1, A-2, A-3, A-A, AM-1, AM-2 (agricultural/agribusiness); C-1, C-2, C-3 (commercial); M-1, M-2, M-3 (industrial); S-1, S-2 (open space); G.S. (government/special public). See § 90501.02.
Overlays: include FP- Flood Plain Hazard Area, GH- Geological Hazard Area, G- Geothermal, among others. See § 90501.03.

Notably, there is no “historic” overlay listed among the County’s overlays in § 90501.03 (Not found in retrieved materials).

Decision-relevant standards at a glance

Topic	What it does	Why it matters	Code Reference
Definition of “Historic structure”	Sets which resources qualify for special handling in floodplain management	Determines eligibility for floodplain variances and protections	§ 91401.07
FP- Flood Plain Hazard Area overlay	Establishes flood-related constraints across base zones	If a historic structure is in FP-, a variance pathway may apply	§ 90501.03 (overlay list)
Floodplain variance for historic structures	Allows minimum necessary relief if historic status is maintained	Enables preservation-sensitive upgrades/repairs in flood zones	§ 91606.01(A)
Urban Lot Split disqualifier	Bars SB 9 lot splits on historic district properties or those on the State Historic Resources Inventory	Historic resources cannot be split under SB 9 in unincorporated areas	§ 90813.06
Dedicated “Historic” overlay/district in zoning	Would create mapped, local historic controls	None identified in County overlay list	Not found in retrieved materials

For base-zone dimensional rules and by-right uses that still apply to historic properties (unless modified via a lawful variance), consult Imperial County Development Standards and the use regulations under the applicable base zone in Imperial County Zoning.

Historic-related districts and overlays (district-by-district)

FP- Flood Plain Hazard Area (Overlay)

Purpose: Manage flood risk; applied on top of base zones. See § 90501.03.
Where it applies: Only on parcels mapped with the FP- overlay on the County’s official sealed zoning maps. See § 90501.04 and § 90501.05 (for boundary rules).
Typical permitted uses: Uses remain those allowed in the underlying base zone (e.g., R-1, C-1, A-2), per the zoning framework in § 90501.02.
Key dimensional/technical standards: Floodplain construction standards apply; for qualified historic structures, a variance can be granted if the work preserves the structure’s historic designation and is the minimum necessary to preserve its historic character. See § 91606.01(A). (Specific numeric flood standards not found in retrieved materials.)
Process notes: Variances are decided considering flood hazards and program purposes; conditions may be attached. See § 91606.01(C)-(E).

Local Historic District or Overlay (Countywide)

Purpose: Would set local historic preservation controls across mapped areas.
Where it applies: Not established by the County’s overlay list in § 90501.03 (Not found in retrieved materials).
Interaction with state triggers: Parcels in a “historic district” or on the State Historic Resources Inventory are ineligible for SB 9 urban lot splits; this is a state-law screen implemented in § 90813.06.

How to use this in practice (unincorporated areas)

Check your base zone and overlays first on the official zoning map. Historic-specific provisions are most likely only if the parcel is in the FP- overlay or if your project involves an SB 9 urban lot split. See § 90501.02–.04.
If you are in a floodplain and your building is a qualifying historic structure (per § 91401.07), consider whether a floodplain variance under § 91606.01(A) is appropriate. Coordinate early with Planning.
For SB 9 urban lot splits, confirm whether the parcel is in a historic district or on the State Historic Resources Inventory; if yes, SB 9 lot splits are barred by § 90813.06.
Regardless of historic status, your project must still meet underlying Imperial County Development Standards, potential Imperial County Design Review if triggered by project type, Imperial County Parking, and Imperial County Signage rules.

Checklist

Confirm your site is in the unincorporated area and identify your base zone and any overlays on the County’s official zoning map (see § 90501.02–.04).
Determine whether the structure qualifies as an “historic structure” per § 91401.07 (national, state, or certified local listings).
If within the FP- overlay, evaluate whether your scope needs a floodplain variance and whether it can be the minimum necessary while preserving historic designation per § 91606.01(A).
If pursuing an SB 9 urban lot split, verify the parcel is not in a historic district and not on the State Historic Resources Inventory; if it is, the split is disqualified under § 90813.06.
Ensure compliance with base-zone Imperial County Development Standards, Imperial County Parking, and any applicable Imperial County Design Review process.
If information is unclear (e.g., map boundaries, listing status), Verify with the jurisdiction.

Risks & Ambiguities

Issue	Why it matters	What to verify
No dedicated historic overlay in the County zoning list	Without a mapped local historic district, countywide “historic” controls are limited	Confirm overlays on the official map per § 90501.03–.04; absence of a historic overlay is Not found in retrieved materials.
Is my building an “historic structure”?	Only qualifying structures get the floodplain variance pathway	Check listing status against the definitions in § 91401.07; if uncertain, Verify with the jurisdiction.
Floodplain variance limits	Variances must be the minimum necessary and cannot remove historic status	Discuss scope early; see § 91606.01(A), (C)-(E).
SB 9 urban lot split exclusion	A parcel in a historic district or on the State Historic Resources Inventory cannot use SB 9	Confirm disqualification under § 90813.06 before proceeding.
Base-zone standards still apply	Even historic projects must meet uses/setbacks unless properly varied	Review base zones in § 90501.02 and applicable Imperial County Development Standards.

Plain-English Summary

In unincorporated Imperial County, there isn’t a special historic district zoning overlay. Historic rules mainly show up in flood zones and SB 9 lot-split eligibility. If your building is a qualifying “historic structure” and you’re in the floodplain, you may seek a carefully limited variance that preserves historic status. Urban lot splits are not allowed on parcels in a historic district or listed on the State Historic Resources Inventory.

Source References

Imperial County Codified Ordinances, Title 9 (Land Use Ordinance), Division 5 (Zoning): base zones and overlay framework, § 90501.02–.04.
Historic structure definition (floodplain management), § 91401.07.
Floodplain variances, including for historic structures, § 91606.01.
SB 9 Urban Lot Split disqualifying criteria (historic district/State Historic Resources Inventory), § 90813.06.
Related internal guides: Imperial County Land Use, Imperial County Overlay Districts, Imperial County Design Review, Imperial County Development Standards, Imperial County Parking, Imperial County Signage, Imperial County Variances and Exceptions, Imperial County Nonconforming Uses.

Information Gaps

Local designation procedures or a mapped “Historic” overlay for unincorporated areas: Not found in retrieved materials.
Any special design review triggers specifically for historic resources: Not found in retrieved materials.
Numeric floodplain development standards referenced by variance provisions: Not found in retrieved materials.

Sources

Retrieved passages

CBC § 1 (§ 1) High relevance
Imperial County Zoning Code (chapter is) High relevance
Imperial County Zoning Code (Section 8) Medium relevance
Imperial County Zoning Code (§ 11) Medium relevance
Imperial County Zoning Code (§ 65915) Medium relevance
CBC § 18954 (Section 18954) Medium relevance
Imperial County Zoning Code (Section 6) Medium relevance
Imperial County Zoning Code (Section 38) Medium relevance

Cited sections

Official Imperial County code library

Frequently asked questions

Does Imperial County have a historic preservation overlay in unincorporated areas?

Not in the zoning overlay list retrieved. The County’s overlays are enumerated in § 90501.03 and do not include a dedicated historic overlay (verify on the sealed zoning map).

How does the County define a “historic structure”?

For floodplain management, a “historic structure” includes properties listed in the National Register, the state inventory, or a certified local program. This definition controls eligibility for certain variances. See § 91401.07.

Can I get relief from floodplain standards for work on a historic building?

Possibly. A variance can be issued for repair or rehabilitation if it won’t jeopardize the building’s historic designation and is the minimum necessary to preserve its character. See § 91606.01(A).

Are SB 9 urban lot splits allowed on historic properties in unincorporated areas?

No. Parcels in a historic district or included on the State Historic Resources Inventory are disqualified from SB 9 urban lot splits under § 90813.06.

Do base zoning standards still apply to historic properties?

Yes. Historic status does not change allowed uses or dimensional standards in your base zone unless relief is granted through a lawful variance. See § 90501.02 and the applicable Imperial County Development Standards.

Is there a special County design review for historic buildings?

Not found in retrieved materials. If your project otherwise triggers Imperial County Design Review, that process would still apply; confirm with Planning.

How do I check whether my parcel is in the FP- Flood Plain overlay?

Use the County’s official, sealed zoning map maintained by Planning; only sealed copies are official. See § 90501.04.

Where can I find rules on signage or parking for historic buildings?

There are no special historic-specific rules retrieved; standard Imperial County Signage and Imperial County Parking requirements apply unless varied. Not found in retrieved materials for historic-specific exceptions.

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