Local zoning · San Marino

San Marino — Overlay Districts

Overlay Districts under the San Marino local zoning and planning code, with the controlling citations.

Last reviewed: July 2, 2026

Overview

San Marino’s zoning chapter does not use a generic “Overlay District” label; instead the code implements extra, cross-cutting controls through Area Districts (the IE/I–VII classifications) and specialized zones such as the H&C (Historical and Cultural) zone. For project-level rules you must check the base zone (for example R-1, C-1, MU-1) plus the applicable area district and any special-zone rules; these interact with the city’s objective development standards, design review, and parking rules. The code’s list of zones and area districts is set out in § 23.01.05 ; if you search for a general “overlay district” the ordinance text does not define a separate overlay mechanism under that name (Not found in retrieved materials).

How San Marino implements overlay-like controls (code basis)

The code establishes formal Area Districts (Estate IE, I, II, III, IV, V, VI, VII) that modify dimensional standards in the R-1 single‑family zone; these function like the city’s primary “overlay” for residential lot-size / yard differences (§ 23.01.05; § 23.02.09) .
The Historical and Cultural (H&C) zone is a special zone with its own permitted uses, hours/attendance limits and conditional-use controls; it operates as a site-specific special district rather than a named “overlay” layer (§ 23.05.01) .
Many development exceptions, conditional uses, and ministerial/by‑right processes (for housing and ADUs) are handled under separate articles (e.g., conditional use and variance rules in Article 07, ministerial/by-right in Article 23) and must be read with the base zone + area district rules (see § 23.07.04 and Article 23) .

District-by-district breakdown

Area District IE (Estate Area District)

Purpose: Applies the largest-lot standards used in the R-1 context; used for estate parcels and exceptional lots. See the list of area districts in § 23.01.05 .
Typical permitted uses: Same uses as R-1 (single‑family residential and customary accessory uses); commercial uses are prohibited in R-1 unless specifically allowed elsewhere § 23.02.01 .
Key dimensional standards (summary below) are governed by the R-1 yard/lot table in § 23.02.09 .
Where it applies: See the City’s zone map; area districts are layered over R-1 parcels per § 23.01.05 . Verify parcel-by-parcel on the map (Verify with the jurisdiction).

Area District I (First Area District)

Purpose & uses: Same approach as IE but smaller statutory parcel area; applicable standards are in § 23.02.09 .
Practical note: Area District I sets the next-highest minimum lot size (30,000 sq. ft.) and associated yard/height rules; confirm which area district your lot is in before estimating allowable building envelope (§ 23.01.05, § 23.02.09) .

Area District II / III / IV / V / VI / VII

Purpose & uses: These progressively smaller area districts (20,000 → 9,000 sq. ft. statutory parcel areas) refine yard dimensions, maximum heights, minimum lot widths, and frontage requirements in the R-1 zone; all set out in § 23.02.09 and created by § 23.01.05 .
Practical: The area district is the first stop for dimensional limits (setbacks, lot size, height) on single‑family parcels. For R-1 projects, follow the R-1 / Area District table in § 23.02.09 exactly; deviations require the normal discretionary relief routes (variance or conditional use) under Article 07 (§ 23.07.04) .

H&C — Historical and Cultural Zone

Purpose: To identify, protect and manage significant historic and cultural properties and their settings; the purpose language is in § 23.18.01 (Historic Preservation article) .
Typical permitted uses: Museums, arboretums, botanical gardens, libraries, galleries, limited retail and food service for visitors, employee housing for staff, schools and similar institutional uses listed in § 23.05.01; many activities and structural changes require a conditional use permit per § 23.05.01.B .
Key constraints and standards:
- Many activities are limited by hours or attendance caps and some outdoor events/filming require a CUP (§ 23.05.01.C and implementing subsections) .
- Designation as a historic landmark triggers review and a Certificate of Appropriateness process under the Historic Preservation article; procedures and hearing steps are in Article 18 (§ 23.18. series) .
Where it applies: Specific parcels are mapped as H&C under the zone map; H&C is a full zone (not simply an overlay) and has distinct permitted/conditional uses § 23.05.01 .

Other special/supplemental districts and controls (functional overlays)

Mixed‑use zones (MU-1, MU-2) and multi‑family zones (RM1, RIH) have their own use tables and development standards that can supersede or interact with other articles; see Article 21 and Article 20 for mixed‑use and multi‑family rules (§ 23.21.02, § 23.20.02) .
The by‑right/ministerial routes for certain housing projects (Article 23) bypass discretionary review when objective standards are met; that process must be read with the base-zone and area‑district rules (§ 23.23.01–.06) .

Quick reference table — most decision‑relevant area‑district standards

Area District	Minimum Parcel Area (statutory)	Typical Max Height	Typical Minimum Front Yard	Typical Side Yard	Typical Rear Yard	Code Reference
IE	60,000 sq. ft.	35 ft.	40 ft.	20 ft.	40 ft.	§ 23.02.09
I	30,000 sq. ft.	35 ft.	40 ft.	20 ft.	40 ft.	§ 23.02.09
II	20,000 sq. ft.	35 ft.	40 ft.	12 ft.	40 ft.	§ 23.02.09
III	17,000 sq. ft.	30 ft.	40 ft.	12 ft.	40 ft.	§ 23.02.09
IV	15,000 sq. ft.	refer table	refer table	refer table	refer table	§ 23.02.09
V	12,000 sq. ft.	refer table	refer table	refer table	refer table	§ 23.02.09
VI	10,000 sq. ft.	refer table	refer table	refer table	refer table	§ 23.02.09
VII	9,000 sq. ft.	refer table	refer table	refer table	refer table	§ 23.02.09

(For the full R-1 area‑district table, use § 23.02.09; the City’s zone map shows which parcels are in which district § 23.01.05.)

How overlay‑style rules interact with other code parts (practical guidance)

Confirm the parcel’s zone and area district first (the area district dictates front/side/rear setbacks, min lot, and height under § 23.02.09) .
Check whether the parcel is in H&C (if yes, consult § 23.05.01 for permitted conditional uses and § 23.18.01 for preservation procedures) .
For design and submittal expectations, follow the design review documentation requirements (e.g., § 23.15.13) and the objective standards referenced by ministerial/by‑right routes (§ 23.23.06) .
For accessory dwelling units, use the ADU article and ministerial ADU process (ADU submittal and development standards) — see § 23.02.01 and the ADU section for process/timelines (§ 23.02.25 reference and the ADU article) .
Parking rules apply per the zone and special district (see parking and § 23.10.02/03) .

Checklist

Verify your parcel’s base zone and area district on the City zone map (Area districts are set out in § 23.01.05) .
Read the R-1 / Area District dimensional table in § 23.02.09 and confirm setbacks, height and minimum lot area for your parcel § 23.02.09 .
If parcel is in H&C, pull § 23.05.01 and Historic Preservation article § 23.18.01 for permitted uses, permitted exceptions and designation procedures .
Prepare design‑review documentation per § 23.15.13 (plans, elevations, landscape info) and check whether your project is ministerial or discretionary .
Confirm parking requirements tied to the zone (C‑1, MU, etc.) in § 23.10.02 / 23.10.03 and include required parking calculations in submittal .
For ADUs, follow the ADU article and ministerial timelines; check ADU development standards and whether a Planning ADU Application is required § 23.02.25 and related ADU subsections .
If your proposal departs from area‑district standards, prepare to file for a variance or conditional use permit under Article 07 (see § 23.07.04) .
Verify any historic‑landmark designation triggers Certificate of Appropriateness or other requirements in Article 18 (§ 23.18. series) .

Risks & Ambiguities

Issue	Why it matters	What to verify
No section explicitly labeled “Overlay District”	Practitioners looking for a generic “overlay” may miss that the city uses Area Districts and special zones to play that role	Confirm the parcel’s Area District or special zone in the City zoning map (see § 23.01.05)
Parcel‑specific area district	Dimensional rules (setbacks, height) change by area district, so a one‑size estimate is unsafe	Check § 23.02.09 for the exact table that applies to your parcel and confirm area district mapping with staff
Historic designation or H&C constraints	H&C has event/hours/attendance limits and many changes require CUP or landmark certificate; design review and preservation procedures apply	If property is H&C or landmark, read § 23.05.01 and Article 18; verify whether Certificate of Appropriateness is required
Interplay with by‑right ministerial housing rules	Some housing projects are approved ministerially if objective standards are met — this can change the review path	Confirm by‑right eligibility and objective standard lists in Article 23 (§ 23.23.01–.06)
ADU process exceptions vs. local overlay rules	State ADU rules preempt some local rules, but local development standards still apply in many cases	Follow the ADU provisions in the municipal code and state law; see the ADU article/subsections for ministerial timelines (§ 23.02.25 / ADU article)

Plain‑English Summary

San Marino does not use a generic “overlay district” label in its zoning text; instead, the city layers Area Districts (IE, I–VII) on top of the R‑1 zone to set lot size, setback and height differences, and it uses special zones such as H&C for site‑specific historic/institutional controls. Always check the parcel’s zone + area district, then read the matching code table (R‑1 area‑district table § 23.02.09) and any H&C or mixed‑use provisions that apply before designing a project .

Source References

§ 23.01.05 (Zones and Area Districts established)
§ 23.02.01 (R‑1 uses permitted; ADU cross‑reference to § 23.02.25)
§ 23.02.09 (R‑1 lot area, height and yard dimensions table)
§ 23.05.01 (H&C uses permitted and conditional uses)
§ 23.05.04 / § 23.05.05 (H&C application procedures; by‑right notes)
Article 18 / § 23.18.01 (Historic Preservation purpose and procedures)
§ 23.15.12 – 23.15.13 (Design review effective date and documentation requirements)
§ 23.10.02 – 23.10.03 (Off‑street parking minimums and rules)
Article 07 / § 23.07.04 (Conditional use / variance revocation and effective dates)
Article 23 / § 23.23.01–.06 (By‑right approval and ministerial plan permit rules)
ADU provisions (process, ministerial review and development standards)

Sources

Retrieved passages

San Marino Zoning Code (article 07) Medium relevance
San Marino Zoning Code (Section are) Medium relevance
San Marino Zoning Code Medium relevance
San Marino Zoning Code (Section 65583.2) Medium relevance
San Marino Zoning Code (section unless) Medium relevance
San Marino Zoning Code Medium relevance
San Marino Zoning Code Medium relevance
CBC § 23.02.10 (section 23.02.10) Medium relevance
San Marino Zoning Code (chapter of) Medium relevance
San Marino Zoning Code (§ 65913.4) Medium relevance
San Marino Zoning Code (Section and) Medium relevance
San Marino Zoning Code (article 07) Medium relevance
San Marino Zoning Code (ARTICLE 21) Medium relevance
San Marino Zoning Code (chapter shall) Medium relevance
San Marino Zoning Code (ARTICLE 04) Medium relevance
San Marino Zoning Code (ARTICLE 16) Medium relevance
San Marino Zoning Code (Section 23.10.03) Medium relevance
San Marino Zoning Code (section 65583.2) Medium relevance
San Marino Zoning Code (ARTICLE 23) Medium relevance

Cited sections

Official San Marino code library

Frequently asked questions

What is an "overlay district" in San Marino's zoning code?

San Marino’s code does not define a generic “overlay district.” Instead, extra controls are applied through Area Districts (IE, I–VII) that modify R‑1 dimensional standards and through special zones such as H&C (Historical and Cultural). See § 23.01.05 and § 23.02.09 .

What are the required setbacks for an R‑1 lot in Area District II?

Setbacks and other dimensional rules are set by the R‑1 / Area District table; Area District II uses the statutory parcel area and corresponding yard dimensions in § 23.02.09 (consult the full table for exact front/side/rear numbers) .

Do I need design review for an addition in an R‑1 area district?

If your project increases square footage or otherwise triggers design review per Chapter 23, you must submit the documentation listed in § 23.15.13; some projects meeting objective standards may be processed ministerially under by‑right rules in Article 23 — check § 23.15.13 and § 23.23.04 .

If my property is in the H&C zone, what uses are allowed?

The H&C zone permits institutional and cultural uses such as arboretums, museums, galleries, gardens, libraries, schools, limited retail and food service for visitors, and related ancillary uses; many activities and structural changes require a conditional use permit under § 23.05.01 .

Can I build an ADU if my parcel is in a special area district or H&C?

ADUs are addressed by the municipal ADU provisions and state law; many ADUs are ministerial but must comply with local ADU development standards and other applicable zone/area‑district rules — see the ADU article and the cross reference in § 23.02.01 and ADU subsections for process and development standards .

Where do I check whether my parcel is in Area District V or in H&C?

The city’s zoning map and the zone/yard map underlying Chapter XXIII show which area district or zone applies. The code establishes the area districts in § 23.01.05; verify the map and talk to Planning staff for parcel confirmation (Verify with the jurisdiction) .

What if my project does not meet the area district dimensional standards?

If your project departs from the area‑district standards, you must pursue discretionary relief (variance or conditional use permit) under Article 07; see revocation/effective‑date rules and the findings required for CUP/variance decisions in § 23.07.04 and related subsections .

Are there attendance/hours caps on events at H&C properties?

Yes. The H&C rules impose vehicle/attendance limits, hours for public visitation and event thresholds that trigger CUP requirements; see § 23.05.01.C and implementing subsections for details and thresholds (events over certain attendance levels require CUP) .

Who enforces area district and H&C rules?

Enforcement duties are assigned to the Planning and Building Director and other City officials in the code; enforcement remedies and penalties are in Article 17 and related enforcement provisions (e.g., nuisance and penalty language) — see § 23.17.01–.04 for enforcement and remedies .

If the code mentions an overlay elsewhere, where is it?

Search the code for “overlay” returns no formal “Overlay District” article; the ordinance uses area districts and special zones instead. For anything that looks like an overlay in other contexts, write “Not found in retrieved materials” and verify with the City (Verify with the jurisdiction) .

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