Local zoning · Ross

Ross — Overlay Districts

Q: How does the Special Building Site **:B** change what I can build on an R-1 lot?

When a parcel has the :B suffix the chapter § 18.32 changes minimum lot area, lot width, side-yard rules, parking and maximum building coverage and floor area ratios for that parcel’s R-1:B subclass; see § 18.32.030 – § 18.32.070 for the numeric standards that apply to each R-1:B subtype. Verify the specific R-1:B subclass on the zoning map.

Q: Will projects in a **:CD** be subject to the same design-review standards as other projects?

:CD explicitly requires Town Council review of plans for buildings and structural alterations and includes review items similar to design review (aesthetics, ingress/egress, parking). Projects in :CD may also be evaluated under the design-review chapter § 18.41 where applicable. See § 18.36.020 and § 18.41.050–100 .

Q: Can the Town impose design/landscape conditions specifically because of a combining district?

Yes. :CD and :O explicitly authorize conditions to protect civic or open-space values; :H authorizes conditions to address hazards. These conditions are part of the discretionary review authority the Town exercises under those chapters. See § 18.36.020 , § 18.37.020 , and § 18.38.020 .

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

Ask a question free See coverage

Last reviewed: July 2, 2026

Overview

In Ross the term used for overlays is "combining districts" — the ordinance establishes four combining/overlay classifications: :B (Special Building Site), :CD (Special Civic), :O (Special Open), and :H (Special Hazard). These combining districts are applied only in combination with the town's base zones such as R-1, C-L, C-D, C-C, P-F, O-S and modify review, approval, and/or use-permit requirements for parcels in those areas. See the Town zoning framework in Ross Zoning for the map incorporation rule and district lists; physical boundaries are shown on the Town's official Zoning Map. § 18.08.010 and § 18.08.020 explain the base and combining district designations. § 18.08.030 requires the Zoning Map be incorporated into the code. parking, design review, development standards, ADUs, and the California Building Standards Code can all be implicated when a combining district applies — see the ordinance chapters cited below for what is required. § 18.08.010 § 18.08.020 § 18.08.030

How Ross uses the word “overlay”

Ross calls overlays "combining districts" and lists them explicitly as combining districts to be applied in combination with general districts. That authority and list are in § 18.08.020.

District-by-district (combining/overlay) breakdown

Note: the ordinance applies the combining district provisions in addition to the base-zone rules (for example R-1 single-family rules). Always read the base zone chapter together with the combining-district chapter cited below.

:B — Special Building Site (combining district)

Purpose: The :B combining district is intended to be applied in combination with R-1 where larger lot sizes or special lot-area rules are needed to preserve established character and development patterns. § 18.32.010.
Typical effect / permitted uses: Uses are those of the underlying general district (usually R-1 single-family residential) but subject to the special lot/coverage/parking and other requirements of the :B rules. See the chapter for when use permits or special calculations apply. § 18.32.010.
Key dimensional standards (decision-relevant): The chapter lays out minimum lot area, lot width, side yard and rear yard rules, parking requirements, maximum building coverage and maximum floor area ratios for different R-1:B subdesignations (e.g., R-1:B-6 through R-1:B-A). See § 18.32.030 through § 18.32.070 for the lot-area, parking, building coverage and floor-area rules; specific FAR figures for R-1:B subtypes are in § 18.32.070.
Where it applies / how imposed: Applied only where approved by Town Council and mapped on the Town Zoning Map; the combining district is listed as a suffix to the base district (for example R-1:B-10). § 18.08.020, § 18.32.010.

Practical guidance: If your property shows a :B suffix on the zoning map, expect different minimum lot and FAR controls than plain R-1 — check § 18.32.030–070 and confirm the specific R-1:B subclass (B-5, B-6, B-10, B-A, etc.) that appears on the map.

:CD — Special Civic (combining district)

Purpose: The :CD combining district protects public, quasi‑public or civic investments adjacent to a parcel by adding review and approval steps. § 18.36.010.
Typical effect / permitted uses: Underlying base uses remain, but building plans and significant alterations are subject to Town Council plan review and additional conditions intended to preserve public-interest objectives. § 18.36.020.
Key standards / review triggers: Prior to issuance of a building permit for new buildings or structural alterations, plans must be submitted to and may be approved by Town Council; Council reviews ingress/egress, parking adequacy, aesthetics and public welfare impacts. § 18.36.020 (1–2).
Where it applies: Typically applied to parcels adjacent to town-owned properties, schools, parks or civic improvements; mapped as a combining district suffix. § 18.36.010.

Practical guidance: Expect mandatory Council review for permit-level changes in :CD areas — factor in public hearings and the town’s design expectations (see the town’s design review chapter for overlap). § 18.36.020

:O — Special Open (combining district)

Purpose: The :O combining district recognizes and protects open-space characteristics where applied. § 18.37.010.
Typical effect / permitted uses: Uses allowed by the base district continue, but the :O requires a use permit for all base-district uses so that impacts on open-space values can be reviewed and conditioned. § 18.37.020.
Key standards: Use permits for any activity permitted by the base district; conditions emphasize conservation, limited development, and preservation of natural terrain/vegetation. § 18.37.020.
Where it applies: Areas needing recognition/protection of open-space characteristics; mapped as a combining district suffix. § 18.37.010.

Practical guidance: If you are in an :O area, plan on discretionary use-permit review even for uses that would otherwise be ministerial in the base zone; expect conditions focusing on habitat, erosion control and landscape preservation (see landscaping and screening). § 18.37.020

:H — Special Hazard (combining district)

Purpose: The :H combining district is applied where natural hazards (slope, seismic, wildfire, erosion, periodic inundation) warrant extra review to protect public health and safety. § 18.38.010.
Typical effect / permitted uses: All base-district uses require a use permit when combined with :H; approved use permits are conditioned to address specific hazards (slope, erosion, soil stability, seismic action, wildfire, inundation). § 18.38.020.
Key standards: Conditions on use permits must recognize the site-specific hazards; the chapter also incorporates mapped areas and directs Council consideration of hazard-specific mitigation in permit decisions. § 18.38.020–030.
Where it applies: Mapped hazard areas shown on the zoning map and applied as a combining suffix (e.g., R-1:H). § 18.38.010 and § 18.08.030 on map incorporation.

Practical guidance: Expect geotechnical, drainage, and fire-safety conditions; projects in :H subareas often require specialist reports and strong mitigation measures. See the town’s design review guidelines for overlap with hillside and hazard review. § 18.38.020

Quick reference table — combining districts (decision-relevant)

Combining district	Main effect (what an applicant must expect)	Typical code reference
:B (Special Building Site)	Different lot-area/width, parking, coverage and FAR rules (R-1:B subclasses). Expect altered minimums and calculations.	§ 18.32.010 – § 18.32.070
:CD (Special Civic)	Town Council plan review required before building permits for new/altered structures; Council evaluates ingress/egress, parking, community impacts.	§ 18.36.010 – § 18.36.020
:O (Special Open)	All base-district uses require a use permit; review/conditions protect open-space values.	§ 18.37.010 – § 18.37.020
:H (Special Hazard)	All base-district uses require a use permit; permits conditioned for slope, erosion, seismic, wildfire, inundation hazards.	§ 18.38.010 – § 18.38.020

Checklist (what an applicant must satisfy when a combining district applies)

Confirm the parcel’s base zone and any combining district suffix on the Town Zoning Map per § 18.08.030.
Read the base-zone chapter (for example R-1 in § 18.16.000 etc.) together with the combining-district chapter (for example § 18.32 for :B).
For :B properties: verify the specific R-1:B subclass and applicable lot/coverage/FAR and parking requirements in § 18.32.030–070; confirm parking calculations with the town as required by § 18.32.040.
For :CD properties: prepare plans for submittal to Town Council and anticipate Council findings on ingress/egress and parking adequacy per § 18.36.020; coordinate possible design review requirements.
For :O and :H properties: file for a Use Permit where required, supply hazard/landscape/erosion/drainage reports as applicable per § 18.37.020 and § 18.38.020.
Expect additional studies (geotechnical, hydrology, fire safety) and conditions of approval for :H areas; check whether municipal design standards or development standards impose further constraints.
Check overlap with other chapters (design review § 18.41, ADU rules § 18.42) and the California Building Standards Code for construction requirements — but treat planning/overlay questions separately from Title 24 requirements.

Risks & Ambiguities

Issue	Why it matters	What to verify
Parcel-specific suffix / subclass (e.g., R-1:B-6 vs R-1:B-A)	Different R-1:B subclasses carry different numeric standards (lot area, FAR). Applying the wrong subclass will produce incorrect design limits.	Verify the exact suffix on the Town Zoning Map and read the matching § 18.32.030–070 entries. (§ 18.08.030; § 18.32.070)
Zoning map boundaries not included in retrieved materials	The code requires map incorporation, but the map itself (parcel-by-parcel overlay extent) is needed to confirm applicability.	Confirm overlay mapping with the Town (Zoning Map) and Planning Department. (§ 18.08.030)
Interaction with ADU provisions	ADU rules are in a separate chapter and state law may restrict local overlay enforcement in some cases.	ADU–overlay interactions are not explicitly described in the combining-district chapters — verify with planning staff and review § 18.42 for ADU-specific limits. (ADU chapter: § 18.42) Not found in retrieved materials for overlay-specific ADU exceptions.
Use permit vs. ministerial approvals	Combining districts often convert otherwise permitted activities into discretionary reviews (use permits). Missing this can lead to denial or stop-work orders.	Check § 18.37.020 and § 18.38.020 for required use permits; plan on discretionary timelines and public notice.
Overlap with design review / Council review	:CD requires Council plan approval; design-review thresholds may also apply to the same project.	Expect to satisfy both § 18.36.020 (Council plan submittal) and the design-review criteria in § 18.41.100 as applicable.

Plain-English Summary

Ross does not use the word "overlay" — it uses "combining districts" (suffixes like :B, :CD, :O, :H) that sit on top of base zones (like R-1) and change how development is reviewed and what numeric standards apply; check the zoning map to see which combine with your parcel and then read the matching combining-district chapter for required permits and conditions. § 18.08.020, § 18.32.010–070, § 18.36.020, § 18.37.020, § 18.38.020.

Information Gaps

The official Town Zoning Map showing the exact parcels with :B, :CD, :O, or :H was not included in the retrieved files; verify overlay boundaries with the Town. (§ 18.08.030)
The ordinance text gives R-1:B subclass numeric standards but the mapping that ties a parcel to a specific R-1:B subclass (e.g., B-5, B-10, B-A) is not in the provided extracts — confirm the parcel’s subclass on the Zoning Map and in Planning Department records. (§ 18.32.070)
Explicit cross-references between combining districts and accessory dwelling unit (ADU) exceptions or state ADU preemption are not stated in the combining-district chapters in the retrieved materials. Verify ADU implications with the Town. Not found in retrieved materials.

Source References

Ross Municipal Code Title 18 — Zoning (Title and chapter table of contents). § 18.04.010, § 18.04.020, Title 18 TOC.
Combining districts designated: § 18.08.010 (general districts) and § 18.08.020 (combining districts); map incorporation § 18.08.030.
Special Building Site (:B) combining district: § 18.32.010 – § 18.32.070 (application, lot area, parking, coverage, floor area ratios).
Special Civic (:CD) combining district: § 18.36.010 – § 18.36.020 (purpose; council plan review and required findings).
Special Open (:O) combining district: § 18.37.010 – § 18.37.020 (open-space application; use-permit requirement).
Special Hazard (:H) combining district: § 18.38.010 – § 18.38.020 (hazard application; use permits conditioned for hazards).
Design review chapter (for overlap with :CD and others): § 18.41.050 – § 18.41.100 (review authority; criteria).
ADU chapter and related cross-references: Title 18 — Chapter 18.42 (Accessory Dwelling Units) — see Title 18 TOC. Not found in the combining-district chapters whether ADUs are treated differently in overlays.

Sources

Retrieved passages

Ross Zoning Code (§10) Medium relevance
Ross Zoning Code (§3) Medium relevance
Ross Zoning Code (§6) Medium relevance
Ross Zoning Code (§2) Medium relevance
Ross Zoning Code (§2) Medium relevance
Ross Zoning Code (Chapter 18.30) Medium relevance
Ross Zoning Code (§1) Medium relevance
Ross Zoning Code (§4) Medium relevance

Cited sections

Official Ross code library

Frequently asked questions

What is a combining district (overlay) in Ross and where is it defined?

A combining district in Ross is what other jurisdictions call an "overlay"; the code lists combining districts :B, :CD, :O, and :H and requires they be applied in combination with base districts. This is defined in § 18.08.020 and the map incorporation requirement is in § 18.08.030.

How does the Special Building Site **:B** change what I can build on an R-1 lot?

When a parcel has the :B suffix the chapter § 18.32 changes minimum lot area, lot width, side-yard rules, parking and maximum building coverage and floor area ratios for that parcel’s R-1:B subclass; see § 18.32.030 – § 18.32.070 for the numeric standards that apply to each R-1:B subtype. Verify the specific R-1:B subclass on the zoning map.

If my lot is in **:O** (Special Open), do I need a use permit for typical residential work?

Yes. :O requires a use permit for all uses that would otherwise be allowed in the base district so the Town can condition activity to protect open-space values. See § 18.37.020.

Does **:H** (Special Hazard) force extra studies like geotech or fire reports?

The code makes all uses in an :H area discretionary (use permits) and requires that permits be conditioned to address natural hazards (slope, erosion, seismicity, wildfire, inundation). In practice you should expect geotechnical, hydrology and fire-safety documentation; see § 18.38.020.

Will projects in a **:CD** be subject to the same design-review standards as other projects?

:CD explicitly requires Town Council review of plans for buildings and structural alterations and includes review items similar to design review (aesthetics, ingress/egress, parking). Projects in :CD may also be evaluated under the design-review chapter § 18.41 where applicable. See § 18.36.020 and § 18.41.050–100.

Where can I find the map to see if my property is in one of these combining districts?

The code incorporates the Town Zoning Map into Title 18 and requires the map to show districts; check the Town’s official Zoning Map (map incorporation rule is § 18.08.030) to confirm whether your parcel carries a combining-district suffix. The map itself was not included in the retrieved text; confirm with the Planning Department.

Do combining districts affect ADU approvals?

The combining-district chapters do not explicitly set out ADU-specific exceptions in the retrieved materials. ADUs are governed by Chapter 18.42; because local ADU rules interact with state law, verify ADU treatment with the Town — the specific overlay–ADU interaction is Not found in retrieved materials.

If my application is in an overlay that requires a use permit, what procedural steps should I expect?

If a combining district converts your activity to discretionary review, expect an application for a use permit with public notice, potential hearings before the Town Council, and required findings/conditions tied to the combining-district purpose (for example, hazard mitigation in :H or open‑space protection in :O). See § 18.37.020, § 18.38.020 and the Use Permit chapter for the procedure.

Can the Town impose design/landscape conditions specifically because of a combining district?

Yes. :CD and :O explicitly authorize conditions to protect civic or open-space values; :H authorizes conditions to address hazards. These conditions are part of the discretionary review authority the Town exercises under those chapters. See § 18.36.020, § 18.37.020, and § 18.38.020.

Ask about any Ross property

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

Start Free Trial