Local zoning · Colusa

Colusa — Overlay Districts

Q: What is an overlay (combining) district in Colusa?

In Colusa an overlay is called a special combining district ; it is mapped on the official Zoning Map and its regulations apply in addition to the base zone. The complete list is in § 2.02 and each combining district’s rules are in its Article (for example Article 19 for A , Article 20 for B , Article 23 for FP ).

Q: If a parcel has an **H35** overlay, what height can I build to?

An H suffix number indicates the maximum permitted height in feet ; so H35 would cap building height at 35 ft as measured per the code’s measurement rules. See § 24.01 for measurement and the AV datum rules for airport hazard areas.

Q: Does the **B** overlay change setbacks or lot size?

Yes — B carries a numeric suffix (for example B10 ) that indicates the required lot area in thousands of square feet; it also sets side yard requirements at 10% of lot width per side (max 15 ft , min 5 ft interior, 10 ft street side). See § 20.01–20.02 .

Q: What if I cannot find an Article for a listed combining district (for example **O**)?

If the combining district is listed in § 2.02 but no Article text is found in your copy of the code (as with O in the retrieved materials), you must verify with City staff or obtain the full Zoning Code document — the list confirms existence but the detailed standards may be in another ordinance or later amendment. Not found in retrieved materials ; see § 2.02 .

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

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Last reviewed: July 1, 2026

Overview

Colusa’s zoning ordinance (titled Zoning Code — Title 17 Zoning) establishes a set of special combining districts (Colusa’s term for overlays) that apply in addition to the base zone where they are mapped. The combining districts are listed in § 2.02 and implemented through discrete Articles (for example "A", "B", "F", "FP", "H", "P", "AO", "HD", plus cannabis rules in Article 21.5) that add use restrictions, dimensional tweaks, or permit requirements to the underlying district. See § 2.02 and the Zoning Map adoption rules at § 3.01–§ 3.02 for where they apply.

Note: this page stays strictly with what the Colusa zoning code itself states about overlay/combining districts (no building-code, housing-law, or tenant-law interpretation). Where the code text for a named combining district is not present in the retrieved materials, I mark that explicitly.

(If you need a parcel-level overlay lookup, verify with the City because the Zoning Map is the controlling map for where overlays apply; see § 3.01.)

How this page uses Colusa terms

Throughout I use the local names exactly as adopted in the ordinance: A (Agricultural Combining District), B (Special Building Site Combining District), CD (Special Civic District Combining District), CM / Article 21.5 cannabis regulations, F (Special Highway Frontage Combining District), FP (Special Floodplain Combining District), H (Special Height Combining District), HD (High Density Housing Combining District), P (Special Parking Combining District), O (Special Divided Ownership District), and AO (Adult-Oriented Combining District) — listed in § 2.02.

District-by-district breakdown

For each combining district below I synthesize the code’s stated purpose, typical permitted uses / requirements, key dimensional or operational standards, and where it applies. All citations cite the controlling Colusa ordinance sections.

Note: references to general development rules (setbacks, lot coverage, etc.) point to the underlying standard zone and the city’s development standards when the combining district defers to the base district.

A — Agricultural Combining District

Purpose: To allow and regulate agricultural and agricultural-related activities on parcels combined with another base district. § 19.01.
Typical permitted uses: All uses of the underlying district plus explicit agricultural uses including animal husbandry, small livestock farming, sale of agricultural products produced on site, and farmworker housing (see § 19.02–§ 19.03).
Key standards: Limits on animal numbers (for example, numeric limits per ½ acre in § 19.02(b)); special yard distances for barns/stables (barns/stables and similar accessory buildings must be ≥ 50 ft from the front property line, ≥ 20 ft from side lines, ≥ 30 ft from any dwelling) in § 19.04.
Where it applies: Combined with any general district as mapped; rules in Article 32 still apply unless specifically modified by Article 19. See § 2.02 and § 19.01.

B — Special Building Site Combining District

Purpose: To require larger lot areas or modified yard depths on special building sites; the "B" designation carries a numeric suffix indicating required lot area (in thousands of sq ft). § 20.01–20.02.
Typical effect: Where a base zone is combined with B, the numeric suffix (example B10) specifies the required lot area (thousands of sq ft). Side yard set‑backs are set at 10% of lot width per side, capped at 15 ft, with minimums of 5 ft (interior) and 10 ft (street side corner yards). § 20.02(b).
Where it applies: Only where the zoning map shows the B# suffix; it supplements the underlying district’s development standards (do not ignore underlying zone rules). § 20.01.

CD — Special Civic District Combining District

Purpose: To coordinate development adjacent to civic centers, parks, and public buildings so development is orderly around public sites. § 21.01.
Typical requirement: No building permit is issued for development in the CD area until the Planning Commission has reviewed and approved plans to ensure orderly development in the civic area (planning review is mandatory). § 21.01.
Where it applies: As mapped around the civic center and public sites; check Zoning Map and follow the planning review process; see design review.

CM / Cannabis rules — Article 21.5 (Cannabis Regulations)

Purpose: Regulate commercial cannabis activities and dispensaries through a dedicated Article (21.5) and a required city-level special use permit and regulatory permit process. § 21.5.01–21.5.03.
Typical permitted locations: Commercial cannabis activities (cultivation, manufacturing, testing, microbusiness, etc.) are allowed only in specified industrial zones (noted in § 21.5.01: Article 12 M‑1, Article 13 M‑2, Article 14 M‑L). Cannabis dispensaries (storefront) are limited to M‑1 with a special use permit. § 21.5.01(a)–(b).
Key permit & operational standards: Must obtain a cannabis business special use permit (city council approval) and a cannabis business regulatory permit; strict security, signage, hours, and operational controls are set out in the Article (see § 21.5.03, § 21.5.08–21.5.11). Many operational details (security, alarm, locked limited-access areas) are spelled out in § 21.5.10 and following. The code also cross-references Chapter 12F and state law.
Where it applies: Only in the industrial zones listed in § 21.5.01; all cannabis activity is subject to the Article 21.5 regime in addition to the underlying zone.

F — Special Highway Frontage Combining District

Purpose: To protect highway-frontage parcels and regulate uses in those areas. § 22.01.
Typical standards: Requires a 20 ft front yard setback where combined; may require screen planting or fencing as a condition of use permits; restricts outdoor advertising sign area (limits expressed as square feet per lineal foot of lot frontage) and allows directional signs under use permit. § 22.02(a)–(d).
Where it applies: Mapped along highway‑frontage parcels as the Zoning Map indicates; F rules apply in addition to the base district and prevail in conflicts. § 22.01.

FP — Special Floodplain Combining District

Purpose: Additional rules for properties in mapped floodplain/floodway areas; the Article expressly governs where combined. § 23.01.
Typical effects and requirements: Some agricultural uses may be allowed without a use permit; other uses require a use permit and must comply with the City of Colusa Floodplain Management Ordinance No. 401 and the standards in Article 23 (§ 23.02(a)–(b)). Floodproofing/elevation, utilities, and construction standards cross‑reference the floodplain ordinance. § 23.02.
Where it applies: Where the Zoning Map shows the FP combining district; FP provisions govern in a conflict with the base zone. § 23.01.

H — Special Height Combining District

Purpose: To set a special maximum height where needed (often for airport hazard areas or other special conditions). § 24.01.
Typical standard: The district symbol H is followed by a number (for example H35) indicating the maximum permitted height in feet measured from average ground elevation. For airport hazard areas the symbol AV may be added and height is measured from a datum; the H designation can also apply to trees or other growth. § 24.01(a)–(b).
Where it applies: Where mapped; the numerical H suffix sets a maximum height that overrides the underlying zone height if lower. § 24.01.

P — Special Parking Combining District

Purpose: To impose parking or loading requirements in addition to the underlying zone. § 25.01–25.02.
Typical standards: Establishes minimum parking and loading requirements or alternative parking rules for parcels where providing standard on-site parking is impractical. See Article 25 and Article 29 (off‑street parking). § 25.02.
Where it applies: Where the Zoning Map includes the P combining district; it supplements Article 29 parking rules and takes precedence in conflict. See the parking guidance.

O — Special Divided Ownership District

Purpose / specifics in code: The combining district label O (Special Divided Ownership District) is listed in § 2.02 as a recognized combining district, but the retrieved materials did not include an Article text giving its detailed regulations. Not found in retrieved materials — verify with the City and the full Zoning Code / Zoning Map.

AO — Special Adult‑Oriented Combining District

Purpose: Regulate adult‑oriented businesses with distance separations, permit requirements and operational limits to protect surrounding uses. § 27.03–27.04.
Typical requirements: Minimum 500‑foot separation from churches, schools, day care, parks, residences, and other adult businesses; required adult‑oriented business regulatory permit (A‑OBRP); CEQA discretionary review applies; hours 6:00 AM–2:00 AM; parking tied to restaurant standards or as determined by the Planning Commission; signage controlled by Article 31. § 27.03(a)–(e).
Where it applies: Where the AO combining district is mapped; the AO rules supplement and, if in conflict, govern over the base zone. § 2.02 and § 27.03.

HD — High Density Housing Combining District

Purpose: Encourage a diversity of housing types and allow higher residential density to meet General Plan housing goals. § 42.01.
Typical effect: Multifamily housing and density increases are permitted in base districts combined with HD; the Article lists permitted uses and defers to Article 32 for some standards. § 42.02.
Where it applies: Only where the HD combining district is mapped; check the Zoning Map and the HD Article for density allowances. § 2.02 and § 42.01.

Quick-reference table — most decision-relevant overlay rules

Combining District	Decision‑relevant rule or permitted uses (short)	Code reference
A	Permits agricultural uses, animal limits per ½ acre, farmworker housing; accessory barns/stables setbacks (50 ft front; 20 ft side; 30 ft from dwellings).	§ 19.02–19.04
B	Numeric suffix (B#) = required lot area (thousands sq ft); side yards = 10% lot width each side (max 15 ft, min 5/10 ft).	§ 20.01–20.02
CD	Planning Commission review required before permits in civic area.	§ 21.01
CM / 21.5	Cannabis facilities limited to M‑1, M‑2, M‑L; dispensaries limited; require cannabis special use + regulatory permits; strict operational/security rules.	§ 21.5.01–21.5.03, § 21.5.08–21.5.11
F	20 ft front setback, screen planting/fencing conditions, sign limits tied to frontage.	§ 22.01–22.02
FP	Supplementary floodplain rules; some ag uses permitted without a use permit; others need use permits and must follow Floodplain Ordinance No. 401.	§ 23.01–23.02
H	H## = max height in feet; AV suffix for airport hazard datum measurement; applies to buildings and growth.	§ 24.01
P	Sets special parking / loading minimums that supplement Article 29.	§ 25.01–25.02
AO	500 ft separation rules, A‑OBRP required, hours and signage limits, parking per Article 29.	§ 27.03–27.04
HD	Allows multifamily/higher density where mapped; used to meet General Plan housing objectives.	§ 42.01–42.02
O	Exists in list of combining districts but detailed Article/regulations not found in retrieved materials.	§ 2.02 — details: Not found in retrieved materials.

Practical guidance / synthesis (plain-English)

Start at the map: determine whether the parcel is overlaid by any combining district on the City’s official Zoning Map (map adoption rules in § 3.01–3.02). If an overlay symbol appears (for example B10, H35, FP, AO), read the specific Article for that symbol — those Articles contain the binding deviations or additional permit obligations. § 3.01–3.02 and § 2.02.
Many overlays do not change the underlying allowed uses but add conditions (e.g., A, F, FP, P) — check whether a use permit / special use permit is required (the Articles explicitly indicate when a use permit is needed). See Article 21.5 for cannabis (special city permits) and § 27.03 for adult‑oriented businesses.
For dimensional questions (setbacks, height), overlays frequently supply either a numeric suffix (e.g., B#, H##) or a stated figure (e.g., 20 ft front setback in F). Where the overlay is silent, the base district standards and development standards apply.

(When the overlay triggers Planning Commission or City Council approval, allow extra time for discretionary review and possible CEQA analysis — the ordinance calls out CEQA review for discretionary permits such as the A‑OBRP in § 27.03.)

Checklist

Confirm mapped overlays on the parcel via the official Zoning Map (§ 3.01–3.02).
Read the combining district Article(s) that apply (e.g., Article 19 for A, Article 20 for B, Article 21.5 for cannabis, Article 23 for FP, Article 24 for H, Article 27 for AO) and note permit triggers and numeric standards (§ 19.02, § 20.02, § 21.5.01, § 23.01, § 24.01, § 27.03).
Check whether a use permit, major use permit, or special regulatory permit is required (see the specific Article and Article 32 permit tables). For cannabis, a cannabis business special use permit and a regulatory permit are required (§ 21.5.03).
Confirm dimensional rules: setbacks, heights (for H the numeric suffix is the maximum), lot area (for B the suffix indicates thousands of sq ft). § 20.02, § 24.01.
For FP (flood areas) check compliance with Floodplain Management Ordinance No. 401 and elevation/floodproofing requirements in Article 23. § 23.02.
If civic area or historic context applies, expect planning commission review (CD), and consult design review or historic preservation as needed.
Confirm parking obligations — overlays may change standard parking rules; consult Article 25 and Article 29 and the city’s parking guidance.

Risks & Ambiguities

Issue	Why it matters	What to verify
Zoning map boundary uncertainty	Overlay location controls whether overlay rules apply; boundaries can be approximate.	Verify the parcel overlay status with the Planning Director or examine the official map; see § 3.02.
“O” (Special Divided Ownership) — no Article text found	The combining district is listed but the ordinance text for its standards was not in the retrieved materials — could change permitted uses or lotting.	Confirm with City staff / full Zoning Code whether Article for O exists and, if so, obtain the Article citation and applicable regs. § 2.02 shows existence; details: Not found in retrieved materials.
Cannabis overlay / special permits (Article 21.5)	Cannabis uses have a two-step permit (special use + regulatory permit) and tight operational requirements; mis‑reading permitted zones causes wasted applications.	Confirm whether your parcel is in an allowable zone (M‑1, M‑2, M‑L), review § 21.5.01–21.5.03, and coordinate with City on cannabis permit processes.
Floodplain (FP) interactions with state / federal flood rules	Additional flood standards and Floodplain Ordinance No. 401 may impose elevation/floodproofing and federal requirements.	Review Article 23 and Floodplain Ord. No. 401; verify base flood elevation and required elevations with City floodplain administrator. § 23.02.
Height limits under H vs. underlying zone	Height suffix (H##) may be lower than the underlying zone height — local measurement rules (datum/AV) can affect allowed building volumes.	Confirm the numeric H on the parcel (e.g., H35), whether AV applies, and how the height is measured (§ 24.01).

Plain-English summary

Colusa’s overlays are called combining districts and are mapped on the official Zoning Map; they add targeted rules (extra setbacks, parking standards, permit requirements, or special use limitations) on top of the base zone. Always check the parcel’s overlays, then read the specific Article (for example Article 19 for A, 20 for B, 21.5 for cannabis, 23 for floodplain, 24 for height, 27 for adult‑oriented businesses) because those Articles contain the binding additional rules and permit triggers.

Source References

Colusa Zoning Code — Title 17 Zoning (Zoning Code, adoption and purpose). § 1.01–1.06.
Official overlay/combing district list: § 2.02 (lists A, B, CD, CM, F, FP, H, HD, P, O, AO). § 2.02.
Zoning Map adoption and interpretation: § 3.01–3.03.
Article 19 — A Agricultural Combining District; § 19.01–19.04 (uses, animal limits, accessory building distances).
Article 20 — B Special Building Site Combining District; § 20.01–20.02 (B# lot area, side yard rules).
Article 21 — CD Special Civic District; § 21.01 (planning commission review).
Article 21.5 — Cannabis Regulations (commercial cannabis locations, permits, operational rules). § 21.5.01–21.5.11.
Article 22 — F Special Highway Frontage; § 22.01–22.02 (20 ft front setback, sign and screening rules).
Article 23 — FP Special Floodplain Combining District; § 23.01–23.02 (floodplain rules; reference to Floodplain Ord. No. 401).
Article 24 — H Special Height Combining District; § 24.01 (H## numeric height and AV/datum).
Article 25 — P Special Parking Combining District; § 25.01–25.02 (parking/loading requirements).
Article 27 — AO Special Adult‑Oriented Combining District; § 27.03–27.04 (500 ft separation, A‑OBRP, parking, signage).
Article 42 — HD High Density Housing Combining District; § 42.01–42.02 (purpose and multifamily use permission).

Sources

Retrieved passages

Colusa Zoning Code (Article 2.) Medium relevance
Colusa Zoning Code (Article 29.) Medium relevance
Colusa Zoning Code (Section 32.01.) Medium relevance
Colusa Zoning Code (Article 23.) Medium relevance
Colusa Zoning Code (Article 17.) Medium relevance
Colusa Zoning Code (section applies) Medium relevance
California Building Code Medium relevance
Colusa Zoning Code (section shall) Medium relevance
Colusa Zoning Code (§ 2) High relevance
Colusa Zoning Code (Article 32.) Medium relevance
Colusa Zoning Code (Article No.) Medium relevance

Cited sections

Official Colusa code library

Frequently asked questions

What is an overlay (combining) district in Colusa?

In Colusa an overlay is called a special combining district; it is mapped on the official Zoning Map and its regulations apply in addition to the base zone. The complete list is in § 2.02 and each combining district’s rules are in its Article (for example Article 19 for A, Article 20 for B, Article 23 for FP).

How do I know whether my Colusa parcel is in an overlay district?

Check the City’s official Zoning Map — the ordinance makes the map part of the code and instructs that mapped overlays control (§ 3.01–3.02). If the map shows a suffix (like B10 or H35) or a combining symbol (like FP or AO), open the corresponding Article for the overlay’s detailed rules.

What can I do on a lot combined with the **A** (Agricultural) district?

Where A is combined with the base zone, you keep the underlying district’s uses but the A Article expressly permits agricultural activities (e.g., animal husbandry, small livestock, on‑site sale of produce, and farmworker housing) subject to the numeric and yard limits in § 19.02–19.04. Check those sections for animal limits and accessory building distances.

If a parcel has an **H35** overlay, what height can I build to?

An H suffix number indicates the maximum permitted height in feet; so H35 would cap building height at 35 ft as measured per the code’s measurement rules. See § 24.01 for measurement and the AV datum rules for airport hazard areas.

How does the **FP** floodplain overlay affect development?

FP requires compliance with Article 23 and the City’s Floodplain Management Ordinance No. 401; some agricultural uses may be allowed without a use permit but many other uses require a use permit and floodproofing/elevation standards. See § 23.01–23.02 and coordinate with the floodplain administrator for elevations and certifications.

Can cannabis businesses locate under an overlay, and where?

Commercial cannabis facilities are permitted only where the code explicitly allows them (Article 21.5): cultivation/manufacturing/testing etc. are limited to M‑1, M‑2, and M‑L (see § 21.5.01), and dispensaries are limited to M‑1 with required city approvals. A city cannabis special use permit and a regulatory permit are required.

Does the **B** overlay change setbacks or lot size?

Yes — B carries a numeric suffix (for example B10) that indicates the required lot area in thousands of square feet; it also sets side yard requirements at 10% of lot width per side (max 15 ft, min 5 ft interior, 10 ft street side). See § 20.01–20.02.

Do overlays ever remove uses allowed in the base zone?

Generally overlays supplement or add conditions to base‑zone regulations and may require additional permits; if an overlay intends to prohibit a specific use it will say so in the overlay Article. Always read both the base district Article and the combining district Article together (see § 2.02).

Do I need design review for civic‑area overlays?

Yes — the CD combining district requires Planning Commission review before building permits are issued for development within the civic district (Article 21, § 21.01). This acts like a localized design/review trigger to protect public-site character. See design review.

What if I cannot find an Article for a listed combining district (for example **O**)?

If the combining district is listed in § 2.02 but no Article text is found in your copy of the code (as with O in the retrieved materials), you must verify with City staff or obtain the full Zoning Code document — the list confirms existence but the detailed standards may be in another ordinance or later amendment. Not found in retrieved materials; see § 2.02.

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