Local zoning · Santa Clara County

Santa Clara County — Overlay Districts

Overlay Districts under the Santa Clara County local zoning and planning code, with the controlling citations.

Last reviewed: July 6, 2026

Overview

In unincorporated areas of Santa Clara County, “overlay districts” are called combining districts. They are applied on top of a base zoning district and, where they conflict, their standards prevail. The Zoning Ordinance explicitly organizes these in Article 3 and directs users to check for any combining district on a parcel because its rules can augment or supersede base zoning. See the organization note in § 1.20.010 (Article 3: Combining Districts) .

Plain-English rule of thumb: if a parcel carries a combining district suffix (like “-d1,” “-sr,” “-n,” or a lot-size “-1 Ac.” tag), the combining district’s standards win over the base zone when they conflict (§ 3.10.020; § 3.20.020; § 3.30.020) .

For a planning primer, see the County’s zoning overview and topic pages on Zoning, Land Use, Development Standards, Design Review, Parking, Signage, and Historic Preservation.

How to read combining districts in unincorporated areas

The base zone (e.g., A, AR, HS, RR, R1, C, etc.) appears first; combining district suffixes come after (e.g., “-sr,” “-d1,” “-n5,” “-1 Ac.,” “-5s”). Combine all that apply; combining rules prevail in conflicts (§ 1.20.010(D)) .
Chapter-specific applicability clauses repeat this rule for each overlay type (e.g., § 3.10.020, § 3.20.020, § 3.30.020, § 3.40.020) .

District-by-District Guide (Combining/Overlay Districts)

Lot Size & Setbacks Combining Districts (Chapter 3.10)

Purpose: Provide parcel-specific minimum lot area and setback standards that supersede base districts to better fit the natural setting and neighborhood patterns in unincorporated areas (§ 3.10.010) .

Applies: Wherever a numeric suffix is added to the base zone (e.g., “-6”, “-1 Ac.”) per § 3.10.020 .

Standard lot-size designators and setbacks are in Table 3.10-1 (e.g., -6, -8, -10, -20, -1 Ac., -2.5 Ac., -5 Ac., -10 Ac., -20 Ac., -40 Ac.) with typical setbacks like 25–30 ft front and 6–30 ft side/rear; these supersede base-zone setbacks (§ 3.10.030, Table 3.10-1) .
Slope-density designators (-1s, -1.75s, -2.5s, -5s, -5/20s, -20s) cap density by average slope using the formula in Table 3.10-2; minimum 30 ft setbacks apply under § 3.10.040(C) .

Typical uses: Same as the base district; these overlays mainly change lot area, density, and setbacks.

Key dimensional standards: See the table below and slope formulas (Table 3.10-2). Average slope S = (0.00229 × I × L) / A, where I = contour interval (ft), L = combined contour length (ft), A = gross area (acres) (§ 3.10.040, notes) .

Where it applies: Any unincorporated parcel with a mapped lot-size or slope-density suffix.

-d Design Review Combining Districts (Chapter 3.20) and -d1 Santa Clara Valley Viewshed

Purpose: Identify visually and environmentally sensitive areas where development must undergo design review to manage visual impacts (§ 3.20.010) .

Applies: A “-d” suffix is added to the base zone; adopted policies can be implemented via numbered subscripts like -d1 (§ 3.20.020) .

Process: Development in “-d” areas is subject to design review under Chapter 5.50 (§ 3.20.030) .
-d1 Santa Clara Valley Viewshed: Tiered thresholds by gross floor area; color light-reflectivity cap (LRV ≤ 45), story poles for hearing cases, and siting/massing controls are specified (§ 3.20.040) .

Typical uses: Follow base zone uses; additional form, color, and siting limits apply.

Where it applies: Mapped hillside areas visible from the valley floor; see the official zoning map references embedded in § 3.20.040 .

-sr Scenic Roads Combining District (Chapter 3.30)

Purpose: Protect the visual character along designated scenic roads, with added design review and signage controls (§ 3.30.010) .

Applies: A “-sr” suffix is added; overlay rules supersede conflicting base-zone rules (§ 3.30.020) .

Triggers: Any structure (including signs) within 100 ft of a scenic road right-of-way requires design review; structures beyond 100 ft do not, unless another overlay/base district requires it (§ 3.30.030(A)) .
Setbacks: Along US 101, a hard 100‑ft no-build setback for buildings and signs applies (§ 3.30.030(C)) .
Signs: One on-site advertising sign plus one “for sale/lease” sign allowed, with specific size limits and exceptions for wineries/ag sales and seasonal sign types (§ 3.30.040) .

Where it applies: Any unincorporated parcel mapped on a designated scenic road corridor (the chapter applies “to all designated scenic roads in unincorporated Santa Clara County”) (§ 3.30.010) .

-n Neighborhood Preservation Combining Districts (Chapter 3.40)

Purpose: Calibrate residential standards in certain urban unincorporated neighborhoods to match area character and address County–city standard mismatches (§ 3.40.010) .

Applies: “-n” plus a number (e.g., -n1, -n5); overlay rules supersede conflicting base-zone rules (§ 3.40.020) .

-n1 (Los Altos area): Floor area caps for single-family lots—FAR ≤ 0.35 up to 10,000 sq ft lots; for larger lots, 3,500 sq ft + 1 sq ft per 10 sq ft over 10,000, capped at 5,700 sq ft. Certain ADU/Urban Primary Unit square footage is excluded from floor area calculations (§ 3.40.030) .
-n5 (Cambrian Park): Fixed setbacks—front 25 ft; sides 8 ft (corner exterior side 10 ft) for dwellings (§ 3.40.070) .

Where it applies: Specific mapped urban unincorporated pockets adjoining cities (e.g., Los Altos-adjacent area; Cambrian Park) per chapter maps and text.

-h Historic Preservation Combining Districts (Chapter 3.50)

Purpose: Preserve designated historic resources and areas; -h districts may add or supersede use and development standards to protect the resource (§ 3.50.010, § 3.50.050–.060) .

Applies: All -h districts follow general provisions (§ 3.50.020); each adopted district may carry custom standards and procedures. Demolition/removal of designated resources requires Board approval (§ 3.50.070) .

-h1 (New Almaden): Purpose is preservation of the New Almaden National Historic Landmark District; allowed uses include single-family residential and agriculture consistent with district intent; additional standards, findings, and review apply (§ 3.50.090) .

Where it applies: Mapped historic areas like New Almaden; any bespoke standards in the adopting ordinance govern (§ 3.50.060(A)) .

-bw Bay Wetlands Combining District (Chapter 3.60)

Purpose: Preserve Bay wetlands while allowing appropriate water-related recreation, education, resource extraction, and open space uses (§ 3.60.010) .

Applies: “-bw” supersedes the base zone; only uses listed in the chapter are permitted (§ 3.60.020) .

Use framework: Uses typically require a use permit; listed examples include salt extraction, boat marinas/maintenance, related educational facilities, and aquaculture (§ 3.60.030) .
Bay fill: Prohibited except where an ecological improvement is demonstrated (§ 3.60.040) .

Where it applies: County-jurisdictional San Francisco Bay wetland areas mapped with “-bw.”

-mh Monterey Highway Use Permit Area Combining District (Chapter 3.70)

Purpose: Allow the continuation/upgrade of certain established non-agricultural, community-serving uses along Monterey Road in South County (outside urban service areas), subject to use permits and Architecture & Site Approval (ASA) (§ 3.70.010) .

Applies: “-mh” on properties documented in the Compliance/Eligibility List; renewals/expansions/changes to less intensive uses require findings and ASA (§ 3.70.020) .

Typical uses: Only those on the eligibility list or those approved under specified allowance pathways (§ 3.70.020, Tables 3.70‑1, 3.70‑2) .

Where it applies: Mapped frontage segments along Monterey Road between Metcalf Road and the County boundary, excluding city urban service areas.

-os Housing Opportunity Sites Combining District (Chapter 3.75)

Purpose: Focus multi-family and limited mixed-use residential development on Housing Element inventory sites, with standards that supersede the base zone (§ 3.75.010, § 3.75.020) .

Applies: Parcels identified in the inventory carry an “-os” designator; alternate standards only via variance or development agreement (§ 3.75.020) .

Process notes: The chapter establishes ministerial streamlining criteria for qualifying projects and community notification; non-qualifying projects proceed through discretionary ASA/use permit procedures (§ 3.75.050–.060) .

Where it applies: Mapped Housing Opportunity Sites in unincorporated areas.

-ps Public Services and Supportive Housing Combining District (Chapter 3.80)

Purpose: Allow emergency shelters, transitional/supportive housing, and agricultural employee housing on government-owned lands to implement Housing Element policies (§ 3.80.010) .

Applies: “-ps” allowances are in addition to base-zone allowances (§ 3.80.020) .

Typical uses/thresholds:

Emergency shelters: Small-scale and large-scale (15–140 beds) by right if meeting criteria; larger capacities may need a use permit (§ 3.80.030) .
Transitional/supportive housing: By right to 140 clients with criteria; larger capacities possible with a use permit (§ 3.80.040) .
Agricultural employee housing (large-scale/permanent): By right to 140 occupants with an emergency-shelter sharing provision; larger capacities possible with a use permit (§ 3.80.050) .

-sm San Martin Use Permit Areas Combining District (Chapter 3.90)

Purpose: Within the San Martin Commercial and Industrial Use Permit Areas, allow certain non-residential uses beyond what the base districts allow, to implement the San Martin planning policies (§ 3.90.010) .

Applies: “-sm” overlay supersedes conflicting base use regulations (§ 3.90.020) .

Where it applies: Mapped San Martin Commercial and Industrial Use Permit Areas.

Quick-reference: Major overlay triggers and standards

Overlay	What it does in unincorporated areas	Key standard(s)	Code Reference
Lot Size & Setbacks (-6 … -40 Ac.)	Supersedes base-zone lot area and setbacks	E.g., -1 Ac.: front 30 ft; sides 20 ft; rear 25 ft	§ 3.10.030, Table 3.10-1
Slope-Density (-1s … -20s)	Caps lots/dwellings by average slope; 30 ft setbacks	S = (0.00229×I×L)/A; 30 ft setbacks	§ 3.10.040 & Table 3.10‑2
-d1 Viewshed	Requires design review; visibility controls	Tiered thresholds; LRV ≤ 45; story poles	§ 3.20.030–.040
-sr Scenic Roads	Design review within 100 ft of ROW; extra signage rules	US 101: 100‑ft no-build for bldgs/signs	§ 3.30.030–.040
-n1 (Los Altos)	Neighborhood-specific residential scaling	FAR ≤ 0.35 (≤10k sf lots); cap 5,700 sf	§ 3.40.030
-n5 (Cambrian Park)	Neighborhood-specific setbacks	Front 25 ft; sides 8 ft (corner 10 ft)	§ 3.40.070
-h (Historic)	Preservation-focused; can supersede base rules	Demolition requires Board approval	§ 3.50.050–.070
-h1 (New Almaden)	District-specific preservation + allowed uses	Single-family, limited agriculture, etc.	§ 3.50.090
-bw Bay Wetlands	Wetland-compatible use list only	Uses by use permit; no bay fill (except ecological benefit)	§ 3.60.020–.040
-mh Monterey Hwy	Lets listed legacy uses continue/upgrade w/ permits	Use permit + ASA; eligibility list governs	§ 3.70.010–.020
-os Housing Sites	Multi-family + limited mixed-use focus; supersedes base	Streamlining + community notification	§ 3.75.010–.020, .050–.060
-ps Public/Supportive Housing	By-right shelters/supportive housing on public lands	Capacities up to 140 (by right)	§ 3.80.010–.050
-sm San Martin	Broader non-residential allowances in mapped areas	Supersedes conflicting base use rules	§ 3.90.010–.020

Practical guidance

When a parcel has both a lot-size overlay and -sr or -d1, expect to satisfy all of them; in conflicts, the combining district text says overlay rules prevail (e.g., § 3.10.020; § 3.30.020) .
In hillside contexts, slope-density and Design Review often work together: the slope overlay limits density and setbacks, while -d1 controls siting, color (LRV), and massing (§ 3.10.040(C); § 3.20.040) .
In -sr corridors, plan early for the 100‑ft design review trigger (and the US‑101 100‑ft no‑build edge for buildings/signs) (§ 3.30.030) .
In -h districts, demolition is a separate Board approval and custom standards can override base-zone allowances; coordinate with Historic Preservation requirements (§ 3.50.060–.070) .
Projects near city limits: some applications in urban service areas face special annexation and city conformance rules; exceptions exist for -os sites (§ 5.20.070(B)(7)) .

Checklist

Confirm the base zoning and every combining suffix on the County zoning map (Article 3 prevails per § 1.20.010(D)) .
For any lot-size (“-6” to “-40 Ac.”) or slope-density (“-1s” to “-20s”) suffix, compute minimum lot area/density and setbacks from Tables 3.10‑1 and 3.10‑2; document average slope per the ordinance formula (§ 3.10.030; § 3.10.040) .
If “-d” or “-d1” applies, prepare color/finish specs (LRV ≤ 45 where required), story poles if a hearing case, and visibility-siting analysis for design review (§ 3.20.030–.040) .
If “-sr” applies, measure 100 ft from the scenic roadway ROW; plan for design review and check US‑101 100‑ft no‑build rule; coordinate signage (§ 3.30.030–.040) .
If “-n” applies, confirm neighborhood-specific caps (e.g., -n1 FAR; -n5 setbacks) (§ 3.40.030; § 3.40.070) .
If “-h” applies, review custom district standards and any demolition restrictions; consult Historic Preservation (§ 3.50.050–.070) .
If “-bw,” “-mh,” “-os,” “-ps,” or “-sm” applies, verify use eligibility thresholds, process (ASA, use permit), and any notice/streamlining provisions (see chapter references above) (§ 3.60; § 3.70; § 3.75; § 3.80; § 3.90) .
Cross‑check parking, landscaping, and any supplemental standards that overlays reference or supersede: Parking, Landscaping and Screening, and Development Standards.

Risks & Ambiguities

Issue	Why it matters	What to verify
Multiple overlays on one parcel	Conflicting standards; overlays prevail	Confirm each suffix and apply overlay precedence per § 1.20.010(D) and chapter‑specific applicability clauses .
Slope-density calculations	Density hinges on average slope; errors can change lot yield	Use the ordinance formula and document inputs; 30‑ft setbacks per § 3.10.040(C); cluster permit options in Chapter 5.45 .
Viewshed visibility (-d1)	Color/massing/siting findings affect approval path	Tier thresholds, LRV ≤ 45, story poles per § 3.20.040; design review triggers in § 3.20.030 .
Scenic road frontage (-sr)	100‑ft design review trigger; US‑101 100‑ft no‑build	Measure from ROW; signage caps in § 3.30.030–.040 .
Historic properties (-h)	Extra findings; demolition is Board-level	District‑specific standards and § 3.50.070 demolition procedures .
Legacy uses (-mh)	Only listed/eligible uses may expand	Eligibility list and findings in § 3.70.020; ASA required .
Housing overlays (-os, -ps)	Streamlining and by-right allowances depend on criteria	Applicability tables and thresholds in § 3.75 and § 3.80; community notice in § 3.75.060 .
Urban service areas	Some permits may hinge on annexation/city conformance	Annexation limitations and exceptions for -os in § 5.20.070; Verify with the jurisdiction .

Plain-English Summary

In unincorporated Santa Clara County, combining districts are add‑on rules that can change setbacks, limit density by slope, trigger design review, protect scenic roads and historic sites, or unlock housing on designated sites. If your zoning string shows a suffix like “-d1,” “-sr,” “-n,” a lot-size tag (like “-1 Ac.”), or a slope tag (like “-5s”), those rules will override the base zone where they conflict—so design around them first, then check everything else.

Source References

Organization and overlay precedence: § 1.20.010 (Articles; Combining Districts prevail)
Lot Size & Setbacks Combining Districts: § 3.10.010–.040; Tables 3.10‑1 & 3.10‑2 (standards, formulas, 30‑ft setbacks)
Design Review Combining Districts: § 3.20.010–.040 (-d; -d1 viewshed tiers, color LRV, story poles)
Scenic Roads Combining District: § 3.30.010–.040 (100‑ft DR trigger; US‑101 setback; signs)
Neighborhood Preservation: § 3.40.010–.030 (Los Altos); § 3.40.070 (Cambrian Park)
Historic Preservation: § 3.50.010–.080 (purpose, applicability, demolition); § 3.50.090 (-h1 New Almaden)
Bay Wetlands: § 3.60.010–.040 (purpose; permitted uses; bay fill finding)
Monterey Highway: § 3.70.010–.020 (purpose; applicability; findings; ASA)
Housing Opportunity Sites: § 3.75.010–.020, .050–.060 (purpose; applicability; process)
Public Services & Supportive Housing: § 3.80.010–.050 (by-right thresholds)
San Martin Use Permit Areas: § 3.90.010–.020 (purpose; applicability)
Annexation/City conformance exceptions: § 5.20.070(B)(7) (exception for -os projects)

Sources

Retrieved passages

Santa Clara County Zoning Code (§ 3.50.090.) Medium relevance
Santa Clara County Zoning Code (§ 2.50.010.) Medium relevance
Santa Clara County Zoning Code (§ 1) Medium relevance
Santa Clara County Zoning Code (§ 3.50.050.) Medium relevance
Santa Clara County Zoning Code (§ 3.20.020.) Medium relevance
Santa Clara County Zoning Code (§ 3) Medium relevance
Santa Clara County Zoning Code (Chapter 5.30.) Medium relevance
Santa Clara County Zoning Code (Chapter 4.50) Medium relevance
Santa Clara County Zoning Code (§ 3.75.060.) Medium relevance
CFC § 65580 (section shall) Medium relevance
Santa Clara County Zoning Code (§ 1) Medium relevance
Santa Clara County Zoning Code (chapter on) Medium relevance
Santa Clara County Zoning Code (§ 1) Medium relevance
Santa Clara County Zoning Code (§ 6) Medium relevance
Santa Clara County Zoning Code (CHAPTER 3.10) Medium relevance
Santa Clara County Zoning Code (§ 4.20.020) Medium relevance
Santa Clara County Zoning Code (§ 3.60.040.) Medium relevance
Santa Clara County Zoning Code (Section 4.20.110) High relevance
Santa Clara County Zoning Code (§ 4.20.110) Medium relevance
Santa Clara County Zoning Code (Chapter 5.45) Medium relevance
Santa Clara County Zoning Code (Article is) Medium relevance
Santa Clara County Zoning Code (§ 1.20.030) Medium relevance
Santa Clara County Zoning Code (§ 4) Medium relevance

Cited sections

Official Santa Clara County code library

Frequently asked questions

What does a “-d1” suffix mean on my unincorporated hillside parcel?

It means the parcel is in the Santa Clara Valley Viewshed design review overlay. New structures are reviewed for color (typically LRV ≤ 45), siting/massing, and sometimes require story poles; larger projects require a public hearing. All “-d” areas require design review per § 3.20.030, with -d1 standards in § 3.20.040 .

I front a scenic road. When is design review required?

If your structure (including signs) is within 100 ft of a designated scenic roadway, design review is required. Along US‑101, no building or sign may be within 100 ft of the right‑of‑way. See § 3.30.030(A), (C) and sign standards in § 3.30.040 .

How do slope-density overlays affect subdivision potential?

A slope-density suffix (e.g., -5s, -20s) uses a formula based on average slope to set the minimum land area per dwelling; you round down to the nearest whole lot. A 30‑ft minimum setback applies from all boundaries. See § 3.10.040 and Table 3.10‑2 .

My lot shows “-1 Ac.” What changes compared to base zoning?

The “-1 Ac.” overlay sets the minimum lot area at 1 acre and fixes setbacks (e.g., front 30 ft, side 20 ft, rear 25 ft) that supersede the base district. Check Table 3.10‑1 in § 3.10.030 .

What is allowed in the New Almaden historic area (-h1)?

The -h1 district protects the New Almaden National Historic Landmark District. Single‑family residential and limited agriculture are allowed subject to special preservation standards, and demolition of designated resources requires Board approval. See § 3.50.090 and § 3.50.070 .

Can legacy commercial uses along Monterey Highway expand?

Only if they’re on the eligibility list and meet findings; expansions/changes typically need a use permit plus Architecture & Site Approval (ASA). See § 3.70.010–.020 and Tables 3.70‑1/‑2 .

What does the -os Housing Opportunity Sites overlay do?

It focuses multi‑family and limited mixed-use residential on specified Housing Element sites, with standards that supersede the base district and include ministerial streamlining criteria and community notification. See § 3.75.010–.020, .050–.060 .

Are signs treated differently along scenic roads?

Yes. The -sr overlay limits the number and size of on-site advertising signs and bars buildings/signs within 100 ft of US‑101. See § 3.30.030–.040 and consult the County’s signage standards for details .

Do neighborhood overlays change my buildable area in urban unincorporated pockets?

They can. For example, -n1 (Los Altos) caps house floor area, and -n5 (Cambrian Park) fixes setbacks that supersede the base zone. See § 3.40.030 and § 3.40.070 .

Where do overlay rules sit relative to other standards like parking or landscaping?

Combining districts override conflicting base district rules, but you still must meet applicable supplemental standards (e.g., Parking, Landscaping and Screening). Overlays often point you to those chapters, and in conflicts the overlay wins (§ 1.20.010(D); chapter applicability clauses) .

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