Local zoning · San Dimas

San Dimas — Overlay Districts

Q: Where are the Affordable Housing Overlay (AHO) areas and what do they permit?

AHO areas are mapped by exhibit/APN list (e.g., AHO‑1 bounded by Monte Vista, Allen, San Dimas Ave and the 210 Freeway; AHO‑2 by APNs shown in an exhibit). They allow evaluation for and development of higher‑density housing consistent with MF‑30 standards (minimum density goals are stated, e.g., 30 du/acre ). § 18.40.050(A–B) .

Q: Do Scenic Highway Overlays (SHO) change allowed uses?

No — SHO does not prohibit uses allowed by the underlying zone; it layers additional design, setback and landscaping requirements (for example 25–50 ft required yards adjacent to certain routes and an underground utility requirement). Check the SHO exhibits for street‑specific setbacks. § 18.108.020–040 .

Q: Can an RPD overlay change the base zoning standards?

Yes — the RPD overlay is intended to allow flexibility and may take precedence over the underlying standards if the planning commission determines it will produce an enhanced development and meet general plan goals; RPD is only used over S‑F or SF‑A zones. § 18.52.010–020 .

Q: Does an overlay automatically allow higher density housing?

Not automatically. For example, AHO overlays identify areas suitable for higher density and require that new higher‑density uses comply with MF‑30 standards and that certain evaluation and approval steps occur before changing existing large public uses to higher density. See § 18.40.040(B) and § 18.40.050 .

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

Ask a question free See coverage

Last reviewed: July 2, 2026

Overview

San Dimas uses several legally recognized overlay districts that modify or add standards to the underlying base zoning. Overlays are mapped by appending abbreviations to the base zone (for example C-H (AHO-1)) and can change permitted uses, development standards, or require special review. See the city's San Dimas Zoning pages and the specific overlay chapters for the controlling rules. Key overlay types in the San Dimas Municipal Code include the Development Standards Overlay (DS), Affordable Housing Overlay (AHO), Scenic Highway Overlay (SHO), and several project-specific overlays such as the Residential Planned Development (RPD) and overlays inside the Downtown Specific Plan. Each overlay is created, mapped and enforced by specific code sections; the summaries below synthesize those rules and point you to the controlling code (§) for verification.

How overlays are shown and prioritized

Overlays are appended to the base zoning on the official zoning map (e.g., (DS-1) or (AHO-1)). The code explicitly requires the overlay abbreviation to be appended to the base zone on the official map. § 18.26.020(B) for DS, § 18.40.030(B) for AHO, § 18.108.030(B) for SHO, and § 18.52.010 for RPD explain this mapping practice. Where overlay standards conflict with the underlying zone, the overlay standards prevail.

District-by-district breakdown

Note: below each district entry gives the purpose, common permitted/affected uses, key dimensional or procedural standards, and where the overlay applies. All statements are tied to the Municipal Code sections cited.

Development Standards Overlay — DS (general)

Purpose: To add development standards and restrictions to maintain single‑family neighborhood character where needed; it supplements the underlying single‑family zones. § 18.26.010.
Where it applies: The overlay may be appended only to property zoned primarily for single‑family use; it may not be applied to specific plans. § 18.26.020(B).
How shown: Abbreviated as DS on the zoning map; a number (e.g., DS-1) may be attached to refer to different standard sets. § 18.26.020(B).
Example specific standards (for DS‑1): geographic boundary described, one‑story limitations on at least 15% of parcels with a 20 ft height cap on those parcels; maximum site coverage on those one‑story parcels 40%; two‑story dwellings limited to 4,000 sq ft and total lot coverage 35%. See § 18.26.030(A)(3–4) for details.
Practical note: DS overlays can override underlying yard/setback or coverage standards where explicitly stated; the code says overlay standards control when conflicts exist. § 18.26.020(A).

Affordable Housing Overlay — AHO (AHO‑1, AHO‑2)

Purpose: To designate areas for higher‑density residential development to meet housing element goals while maintaining compatibility with surrounding uses. § 18.40.010.
Permitted Uses: New higher‑density residential uses are controlled by the MF‑30 standards; existing underlying uses remain permitted. § 18.40.020 and § 18.40.040(B).
Mapping & designation: Shown as AHO appended to base zone; may include a number to denote a particular overlay standard (e.g., AHO‑1). § 18.40.030(B).
Geographic specifics:
- AHO‑1: Bounded by Monte Vista Ave (west), Allen Ave (south), San Dimas Ave (east) and the 210 Freeway (north). The chapter sets a minimum acreage/density goal (minimum 3.83 acres at 30 du/acre to accommodate ~75 units) and a requirement that parcels >1 acre be evaluated for higher density before changing use. § 18.40.050(A).
- AHO‑2: Boundaries are defined by APNs and map exhibit; establishes a minimum 3.3 acres at 30 du/acre to accommodate ~100 units; similar “change of use” evaluation and standards of review apply (access, utilities, compatibility, ability to meet density). § 18.40.050(B).
Practical note: New multifamily development must meet Chapter 18.44 MF‑30 standards; existing uses continue under their underlying zone until a higher‑density change is approved. § 18.40.020; § 18.40.040(B).

Scenic Highway Overlay — SHO

Purpose: Protect visual character along designated scenic corridors; apply supplemental yards, landscaping, and utilities requirements adjacent to designated routes. § 18.108.010.
Permitted Uses: Does not prohibit uses allowed in the underlying zone; it layers additional standards. § 18.108.020.
Mapping: Mapped as SHO appended to base zone on the official zoning map. § 18.108.030(B).
Key development standards: Required yards adjacent to designated streets must be void of structures and fully landscaped; example setbacks include 25 ft for Foothill Boulevard (with exceptions), 50 ft for Via Verde (typical), and 35–50 ft for Puente Street depending on side; utilities must be placed underground; landscaping and building placement must protect views. See § 18.108.040(A–D) for the full list and Exhibits.
Practical note: The overlay identifies street-specific setback requirements in exhibits; where a street isn’t listed, setback will be determined at time of designation. § 18.108.040(A)(4).

Residential Planned Development Overlay — RPD

Purpose: Provides flexibility and enhanced design for residential projects (integrated planning, preserve natural features, flexible standards). § 18.52.020.
Mapping & application: The designation RPD is appended to the underlying zoning on the official map; RPD may only be applied over S‑F or SF‑A principal zones. § 18.52.010.
Uses: Permits uses of the underlying zone and additional open space uses (parks, clubhouses, pools) as listed; the RPD standards may take precedence over the underlying zone if the planning commission finds they produce an enhanced development. § 18.52.010–030.
Practical note: RPD is a discretionary overlay intended to authorize deviations from standard single‑family rules in exchange for an integrated site plan and amenities; plan approval and design review are expected components of an RPD proposal. § 18.52.010–020.

Downtown Specific Plan — overlays inside a Specific Plan

The Downtown Specific Plan divides the area into sub‑areas and explicitly includes two overlays: Town Core Commercial Overlay and Housing Element Sites Overlay; the Specific Plan governs uses and development standards within its boundaries and the plan itself may contain overlays and special designations. § 18.50.030–040.
Practical note: Specific plans can effectively replace standard zoning within their mapped boundary and the Specific Plan text/exhibits control. The Municipal Code requires consistency with the Specific Plan and allows the planning director or council to process amendments per the code’s amendment procedures. § 18.50.010–060.

Quick reference table — decision‑relevant items

Overlay / Item	Typical effect (what changes)	Where / how shown	Code reference
DS (DS‑1)	Special single‑family standards (one‑story parcel quota, height limits, coverage caps)	Appended as DS (or DS‑1) on zoning map; only over single‑family zones	§ 18.26.010–030
AHO (AHO‑1 / AHO‑2)	Enables MF‑30 density on mapped areas; requires evaluation before change of existing large parcels	Appended (AHO‑#) on zoning map; geographic exhibits define boundaries	§ 18.40.010–050
SHO	Additional setbacks, landscaping, underground utilities, view protection for corridors	Appended (SHO); exhibits show street‑specific setbacks	§ 18.108.010–040
RPD	Flexible planned‑development standards, additional open‑space uses; may supersede base standards if approved	Appended RPD after base zone (only over S‑F / SF‑A)	§ 18.52.010–030
Downtown Specific Plan Overlays	Town Core Commercial Overlay; Housing Element Sites Overlay — specific rules in the Specific Plan document	Specific Plan map/exhibits control inside plan area	§ 18.50.030–040

Practical guidance & connections

If your project is in an overlay, verify the map notation on the official zoning map and the overlay exhibit: overlays are shown by appended abbreviations (DS, AHO, SHO, RPD) per § 18.26.020(B), § 18.40.030(B), § 18.108.030(B) and § 18.52.010.
Expect overlay-specific development standards to control where they conflict with the underlying zone; always check both the overlay chapter and the underlying zone's standards in the code. § 18.26.020(A).
Design and site plan requirements are common in overlays (RPD/DS/Specific Plans); refer to the city's San Dimas Design Review procedures and to the San Dimas Development Standards for how overlays interact with setbacks, coverage, and building height rules. If your proposal includes parking changes, consult the San Dimas Parking chapter as overlays defer to or reference parking rules where noted.
Signage, landscaping and utilities: overlays often require landscaping and sign compliance — see the San Dimas Signage and San Dimas Landscaping and Screening rules; SHO explicitly requires underground utilities adjacent to corridors. § 18.108.040(D).
If your overlay contemplates higher density housing, consult the San Dimas ADUs and state rules; note that the overlay says new higher‑density housing must meet Chapter 18.44 MF‑30 standards — check both local MF‑30 rules and the California Building Standards Code for construction requirements. § 18.40.040(B).

Checklist (what an applicant must satisfy)

Confirm overlay notation on the official zoning map (look for DS, AHO, SHO, RPD appended to the base zone). § 18.26.020(B); § 18.40.030(B); § 18.108.030(B); § 18.52.010.
Read the overlay chapter for required setbacks/landscaping/utility requirements (e.g., SHO setback exhibits; DS‑1 one‑story parcel rules). § 18.108.040; § 18.26.030.
Verify whether the overlay imposes additional density or requires evaluation before changing existing public or large‑acre uses (AHO change‑of‑use rules). § 18.40.050.
Prepare site plans and design materials consistent with overlay objectives (RPD and Specific Plans require integrated design and may require planning commission review). § 18.52.020; § 18.50.040.
Demonstrate compliance with referenced development chapters (e.g., MF‑30 standards if proposing higher density under an AHO). § 18.40.040(B).
Check related chapters for parking, signage, landscaping and nonconforming issues and obtain any required determinations/permits. See San Dimas Parking, San Dimas Signage, San Dimas Landscaping and Screening and San Dimas Nonconforming Uses.

Risks & Ambiguities

Issue	Why it matters	What to verify
Overlay boundary uncertainty	Overlays (AHO, DS, SHO) rely on exhibits/APN lists — small map differences change which rules apply	Verify the official zoning map and overlay exhibit in the Planning Division; confirm APNs listed in AHO‑2 exhibit. § 18.40.050(B).
Conflicts between overlay and underlying standards	Overlays state they prevail where conflicts exist, but not every conflict is explicit	Confirm which specific standards (setbacks, height, coverage) are modified in the overlay chapter; if unclear, ask the Community Development Director. § 18.26.020(A).
Applicability to parcels within Specific Plans	Specific Plan regulations supersede typical zoning inside the plan; an overlay outside the specific plan may not apply the same way	Check whether the parcel sits inside a Specific Plan boundary (e.g., Downtown Specific Plan). § 18.50.020–040.
Exact setback measurements for SHO on non-listed streets	SHO lists named streets with setbacks and says other streets are determined at time of designation	For streets not explicitly listed in the exhibits, verify the adopted exhibit or the staff determination at designation time. § 18.108.040(A)(4).
Applicability to ADUs and accessory uses	The ordinance directs higher‑density standards for new housing in AHOs but does not explicitly address ADU treatment within overlays in the overlay chapters	Not found in retrieved materials — verify with the Planning Division and reconcile with local ADU rules and state law. Verify with the jurisdiction.

Plain-English Summary

If your property carries a San Dimas overlay like DS, AHO, SHO, or RPD, the overlay adds or changes rules on top of the base zone (for example special setbacks, density targets, one‑story parcel rules, or scenic setbacks). Overlays are mapped on the official zoning map and their chapter in the Municipal Code tells you exactly what changes — always check the overlay chapter and the underlying zone rules before designing a project.

Information Gaps

Precise treatment of accessory dwelling units (ADUs) inside each overlay is not specified in the overlay chapters we retrieved. Not found in retrieved materials. Verify with the Planning Division and review California ADU law.
The full graphic Exhibits (map images referenced for SHO, AHO boundaries, DS‑1 exhibits) were not included in the text snippets available; the exact exhibit drawings must be checked on the official zoning map/exhibits. Not found in retrieved materials.
Any administrative procedures (application forms, ministerial vs. discretionary steps, fee schedules) associated with overlay approvals are not reproduced here — verify procedural requirements with the Community Development Department. Not found in retrieved materials.

Source References

San Dimas Municipal Code, Chapter 18.26 (Development Standards Overlay) — § 18.26.010–030.
San Dimas Municipal Code, Chapter 18.40 (Affordable Housing Overlay) — § 18.40.010–050 (AHO‑1, AHO‑2).
San Dimas Municipal Code, Chapter 18.108 (Scenic Highway Overlay) — § 18.108.010–040 (setbacks, exhibits).
San Dimas Municipal Code, Chapter 18.52 (Residential Planned Development Overlay — RPD) — § 18.52.010–030.
San Dimas Municipal Code, Chapter 18.50 (Downtown Specific Plan — includes Town Core Commercial Overlay and Housing Element Sites Overlay) — § 18.50.010–060; § 18.50.030.

Sources

Retrieved passages

San Dimas Zoning Code (section shall) High relevance
San Dimas Zoning Code (chapter which) High relevance
San Dimas Zoning Code (§ 18.26.010.) High relevance
San Dimas Zoning Code (§ 1) High relevance
San Dimas Zoning Code High relevance
San Dimas Zoning Code (§ 18.50.050.) High relevance
San Dimas Zoning Code (§ 1) Medium relevance
CPC § 18.528.010 (Article I.) Medium relevance

Cited sections

Official San Dimas code library

Frequently asked questions

What is an overlay district in San Dimas?

An overlay district in San Dimas is a mapped regulatory layer appended to a base zoning designation that adds or modifies rules (setbacks, coverage, density, design objectives) for the parcels within that overlay; overlays are shown by appending abbreviations (for example DS, AHO, SHO, RPD) to the base zone on the official zoning map. § 18.26.020(B); § 18.40.030(B); § 18.108.030(B); § 18.52.010.

What does the Development Standards Overlay (DS) do?

The DS overlay adds development rules to single‑family areas to preserve neighborhood character and allows numbered overlays (e.g., DS‑1) with tailored rules such as one‑story parcel quotas, 20 ft building height caps on those parcels, and parcel coverage limits; the overlay controls where there is a conflict with the base zone. § 18.26.010–030.

Where are the Affordable Housing Overlay (AHO) areas and what do they permit?

AHO areas are mapped by exhibit/APN list (e.g., AHO‑1 bounded by Monte Vista, Allen, San Dimas Ave and the 210 Freeway; AHO‑2 by APNs shown in an exhibit). They allow evaluation for and development of higher‑density housing consistent with MF‑30 standards (minimum density goals are stated, e.g., 30 du/acre). § 18.40.050(A–B).

Do Scenic Highway Overlays (SHO) change allowed uses?

No — SHO does not prohibit uses allowed by the underlying zone; it layers additional design, setback and landscaping requirements (for example 25–50 ft required yards adjacent to certain routes and an underground utility requirement). Check the SHO exhibits for street‑specific setbacks. § 18.108.020–040.

Can an RPD overlay change the base zoning standards?

Yes — the RPD overlay is intended to allow flexibility and may take precedence over the underlying standards if the planning commission determines it will produce an enhanced development and meet general plan goals; RPD is only used over S‑F or SF‑A zones. § 18.52.010–020.

If my lot is in the Downtown Specific Plan, do overlay rules still apply?

Inside the Downtown Specific Plan area the Specific Plan controls uses and development standards; the plan also contains overlays (Town Core Commercial Overlay and Housing Element Sites Overlay). Where the Specific Plan and Municipal Code conflict, the Specific Plan provisions govern within its boundaries. § 18.50.020–040.

How do overlays affect parking and signage requirements?

Overlays typically reference or defer to the city's standard parking and signage chapters. Always check the overlay chapter for direct references and then consult the city's parking and sign rules; for parking rules consult the San Dimas Parking chapter and for signage the San Dimas Signage chapter. Overlay chapters often require compliance with those chapters. Not all overlays rewrite parking—verify with the code text.

Does an overlay automatically allow higher density housing?

Not automatically. For example, AHO overlays identify areas suitable for higher density and require that new higher‑density uses comply with MF‑30 standards and that certain evaluation and approval steps occur before changing existing large public uses to higher density. See § 18.40.040(B) and § 18.40.050.

Where do I find the exhibit maps that show overlay boundaries?

The Municipal Code chapters reference exhibits and maps that define overlay boundaries (for AHO, DS‑1, SHO); those exhibits are part of the official zoning map and the specific chapter appendices — check the Planning Division’s map/exhibit files and the chapter exhibits referenced in the code. § 18.40.050; § 18.26.030; § 18.108.040.

Ask about any San Dimas property

Get a cited, plain-English answer on San Dimas zoning, setbacks, FAR, ADUs and permits — for any address.

Start Free Trial