Local zoning · Solano County

Solano County — Nonconforming Uses

Q: If my nonconforming structure is damaged, can I rebuild it?

If damage exceeds 60% of the structure’s assessed value, the rebuilt structure must comply with current zoning and loses nonconforming status; for lesser damage, limited rebuilding is allowed subject to the code’s repair and expansion rules. § 28.114(C)(2) .

Q: How long can a nonconforming use sit idle before I lose it?

If the actual operation ceases for six months continuously, the county presumes abandonment and your site must thereafter comply with current zoning. Owners can rebut the presumption with proof. § 28.114(F) .

Q: My confined animal facility predates 2005. Can I expand it?

Facilities legally established prior to May 3, 2005 may be grandfathered as nonconforming but are not allowed to expand (in animals or developed area) unless they meet current standards for setbacks, water protection, and other listed requirements in § 28.71.30 . Check the facility’s establishment date and proposed changes against those standards.

Nonconforming Uses under the Solano County local zoning and planning code, with the controlling citations.

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Last reviewed: July 3, 2026

Overview

This page summarizes how the Solano County Zoning Ordinance regulates nonconforming uses, nonconforming structures, and nonconforming lots in the county’s unincorporated areas. It explains the county’s key rules (what you may repair, rebuild, expand, or lose), highlights district-specific exceptions (for the Suisun Marsh, certain agricultural/residential districts, and confined-animal operations), and shows the approvals you’ll typically need. The primary controlling rule is § 28.114 of the Zoning Ordinance.

Important related topics (permit steps, site standards and reviews) are covered elsewhere on GoCodebook: see the county overview and the pages for Solano County zoning & planning overview, Solano County Zoning, and the county Development Standards.

Core County Rules (plain-English synthesis of the ordinance)

The county treats any legally established land use, building, structure, or lot that no longer meets current zoning rules as a nonconforming situation (defined in the ordinance as “Nonconforming Lots, Buildings, Structures, Uses of Land”). § 28.114 sets the overall framework.
Continuation: A lawful nonconforming use may continue but cannot be enlarged, extended, or made to occupy a larger area than when it became nonconforming. § 28.114(C).
Repairs / Maintenance: Ordinary maintenance and repairs are allowed; structural alterations are generally prohibited unless expressly allowed. Work that repairs or improves a nonconforming structure may not exceed 25% of the structure’s assessed value in any one-year period, unless another provision applies. § 28.114(C)(1).
Destruction / Rebuild: If a nonconforming building is damaged or destroyed by fire or other hazards to more than 60% of its assessed value, it cannot be rebuilt as nonconforming; the rebuilt structure must meet current zoning rules (except where an exception applies). § 28.114(C)(2).
Abandonment / Termination: If the operation of a nonconforming use ceases for a continuous period of six months, the county presumes abandonment and the site must conform to current rules thereafter (owner can rebut with proof). § 28.114(F).
Use Permits and Grandfathering: Any activity that requires a use permit is treated as nonconforming until a use permit is obtained; approval of a new use permit extinguishes any prior grandfathered rights for the nonconforming situation. § 28.114(E); see also § 28.106 for use-permit procedures.
Zoning Clearance: Before issuing building, grading, well, septic, business licenses, or other permits affecting a nonconforming use or structure, the Director of Resource Management must issue a zoning clearance that documents the extent of nonconformity and allowable repairs or alterations. § 28.114(G); see also § 28.109 for zoning-clearance operations.
Nonconforming Lots: A lot lawfully created before current zoning that does not meet current lot-area, frontage, or access standards may still be developed if the Director determines the proposed development otherwise complies with the Chapter’s provisions. § 28.114(D).
Exceptions: Prior valid permitting/commencement-of-construction and limited historic exceptions for certain companion/secondary living units are recognized by the code; see § 28.114(H) and the development standards for accessory/secondary units. § 28.114(H).
Site Development / Parking / Signs: All nonconforming uses must still comply with Article IV site-development standards, including parking and other project elements, wherever those standards apply to ongoing improvements. See Section 28.90+ (Article IV) and the county’s parking rules. Solano County Parking
Design & Architectural Review. Certain expansions or projects may trigger architectural or design review under § 28.102 and related processes. Solano County Design Review

District-by-district (where the ordinance prescribes district-specific nonconforming rules)

The ordinance mostly applies the same base nonconforming rules (§ 28.114) across districts, but several districts and use-types have special provisions. Below are districts and use-types where the code explicitly modifies or clarifies nonconforming treatment.

A-SM (Suisun Marsh Agricultural Districts: A-SM-80, A-SM-160)

Purpose & where it applies: Preserves lands adjacent to the Suisun Marsh and limits intensive uses near the marsh. See Table 28.22A and § 28.22.20.
Nonconforming rule: Uses established prior to 1977 that do not conform to Table 28.22A are nonconforming under § 28.114, but the ordinance explicitly allows non‑substantial changes, alterations, and additions within the existing project footprint when approved through a marsh development permit under § 28.104 — provided the overall development footprint is not expanded. § 28.22.20(F) and § 28.114.
Practical effect: If your nonconforming project sits in the marsh area, you may be able to change or repair buildings inside the same footprint (subject to marsh-permit rules and environmental controls), but you cannot expand the developed area. Solano County Overlay Districts

A, A-SV-20, ATC, ATC-NC, R-R, R-TC (Agricultural & rural residential districts)

Purpose & typical uses: These districts contain agricultural operations, primary dwellings, and—subject to district rules—secondary dwellings or accessory structures (see Table 28.23A, Table 28.32A/B).
Secondary dwellings / guest houses: A secondary living unit that legally existed before specific district cut‑off dates (for example, prior to October 27, 2006 in R-R, June 13, 2008 in A or R-TC, and February 1, 2011 in A-SV-20, ATC, ATC‑NC) is considered legal nonconforming and is subject to § 28.114; such units may continue but cannot be enlarged or modified in ways that violate the nonconforming rules unless the code allows. Conversions of existing guest houses may be allowed to secondary dwellings or ADUs if they meet conversion rules and applicable conditions. § 28.72 and § 28.114.
Size & expansion allowances for dwellings: For secondary dwellings the ordinance sets dimensional caps (e.g., maximum 2,400 sq ft; detached secondary units generally limited to 80% of the primary dwelling’s floor area; attached limited to 50%, or other listed alternatives). For pre-existing nonconforming dwellings the code allows rebuilding when damaged and limited expansion in some cases (for example up to 25% of existing footprint under certain provisions). See § 28.72.20 / § 28.72.30 and § 28.114(C).
Permitting & zoning clearance: Any work on these nonconforming dwellings that requires a building, grading, septic, or well permit must first obtain a zoning clearance from the Director that documents permitted repairs/alterations. § 28.114(G) and § 28.72.

Confined Animal Facilities / Animal Operations

Where in the code: Standards and categories are in § 28.71.30 (animal facilities) and related tables.
Nonconforming (grandfathered) status: Any confined animal facility (dairy, stockyard, feedlot, etc.) legally established prior to May 3, 2005 that does not meet later standards may be treated as a legal nonconforming use. However, nonconforming confined animal facilities may not be allowed to physically expand (area or number of animals) unless they meet the standards for setbacks, water protection, etc., listed for their size (Small/Medium/Large). § 28.71.30 and related subsections; see also § 28.114 for general rules.
Key numeric standards that affect nonconformance: setback minima (examples: 200 ft from property line for small facilities; greater distances for medium/large; unique miles-from-city-SOIs rules), groundwater-monitoring and pond design standards apply on rebuilds and expansions — check § 28.71.30 for the full minimums.

Quick Reference Table — Most decision‑relevant nonconforming standards

Topic	What the ordinance lets you do	Code Reference
Continue an existing nonconforming use	May continue but not enlarge, occupy more area, or extend beyond original footprint (except limited exceptions).	§ 28.114(C)
Repairs / ordinary maintenance	Allowed; structural alterations generally prohibited; repairs limited to 25% of assessed value in any one year (unless other provisions apply).	§ 28.114(C)(1)
Damage > 60% (destruction)	If damage > 60% of assessed value, rebuild must meet current zoning (not treated as nonconforming).	§ 28.114(C)(2)
Abandonment	Continuous cessation ≥ six months presumed abandonment; use must thereafter conform.	§ 28.114(F)
Nonconforming lots	May be developed if Director finds compliance with other Chapter provisions.	§ 28.114(D)
Suisun Marsh (A‑SM)	Non‑substantial changes allowed within existing footprint with a marsh development permit; footprint may not expand.	§ 28.22.20(F) and § 28.104
Secondary dwellings & guest houses	Older pre‑existing units in specific districts are legal nonconforming; conversions to lawful ADUs/secondary units allowed if conditions met.	§ 28.72 & § 28.114
Confined animal facilities	Facilities established prior to May 3, 2005 may be grandfathered but may not expand unless current standards are satisfied.	§ 28.71.30 and § 28.114

Checklist (what an applicant must satisfy when dealing with a nonconforming situation)

Determine whether the use/structure/lot was lawfully established prior to the controlling ordinance change (document title, permits, photos, assessor’s records). Verify dates that create nonconforming status. Verify with the jurisdiction. § 28.114(H).
Obtain a zoning clearance from the Director of Resource Management that documents the extent of the nonconformity and the permissible scope of repairs, alterations, expansion, or rebuilding. § 28.114(G).
If a use permit is required for your proposed activity, prepare and file it (approval will supersede prior grandfathered rights). § 28.114(E) and § 28.106.
For property in the Suisun Marsh, prepare a marsh development permit application and environmental controls (erosion, runoff). § 28.22.20(F) and § 28.104.
For secondary/guest-house conversions or ADUs: confirm eligibility (pre‑existing date, owner‑occupancy/other conditions where required), comply with conversion standards and apply for building permits. See § 28.72 and county ADU conversion rules; check state ADU law constraints. California ADU law
For confined animal facilities: document lawful establishment date and, if expanding or reconfiguring, demonstrate compliance with setback, groundwater monitoring, and pond design minimums in § 28.71.30.
Prepare plans addressing parking, signage, and other site-development standards in Article IV (and get any required design/architectural approval). Solano County Parking Solano County Design Review

Risks & Ambiguities

Issue	Why it matters	What to verify
Did the use actually cease for six months?	A six‑month cessation creates a presumption of abandonment, eliminating nonconforming rights.	Confirm evidence of continuous operation (business records, utility bills). Get a zoning‑clearance determination. § 28.114(F).
Value threshold for “destruction”	If damage > 60% of assessed value, you lose nonconforming status on rebuild.	Obtain assessor’s valuation and a county determination; consider insurance/appeals. § 28.114(C)(2).
What counts as “structural alteration”?	Different rules apply to ordinary repairs vs. structural work; exceeding 25% of assessed value can be restricted.	Ask the Director for a zoning clearance and interpretations before permitting work. § 28.114(C)(1).
Suisun Marsh — footprint vs. use changes	Marsh rules allow only non‑substantial changes inside existing footprint; environmental approvals still required.	Verify whether your site is in the marsh management areas and whether a marsh development permit (28.104) is required. § 28.22.20(F).
Confined animal facility grandfather date	If the facility predates May 3, 2005, it may be legal nonconforming — but expansions are tightly constrained.	Confirm establishment date and whether proposed changes meet § 28.71.30 standards.
Secondary dwelling conversion rules	Dates, owner‑occupancy rules, or prior conditional use permits affect eligibility.	Check the specific district date cutoffs and conversion conditions in § 28.72 and § 28.114.

Plain‑English Summary

If your use or building in unincorporated Solano County legally pre‑dates the current rules, you can often keep it—but you usually cannot grow it, rebuild it as-is if it’s heavily damaged, or let it sit idle for six months or more without losing that right. Before fixing, converting, or expanding anything that’s nonconforming, get a zoning clearance and follow the county’s district rules (Suisun Marsh and agricultural/animal operations have special limits). § 28.114 is the controlling rule.

Source References

§ 28.114 Nonconforming Uses — Solano County Zoning Ordinance (Nonconforming rules: continuance, repairs, destruction threshold, abandonment, zoning clearance, exceptions).
§ 28.22.20 Suisun Marsh Agricultural District (nonconforming uses inside Suisun Marsh; marsh development permit requirements; footprint limitation).
§ 28.72 (Residential uses; secondary dwellings, guest house, conversion/size and setback rules tied to nonconforming status).
§ 28.71.30 (Animal facilities — Small/Medium/Large standards; grandfathering of confined animal facilities predating May 3, 2005).
§ 28.104 (Marsh Development Permit — required process for Suisun Marsh modifications).
Solano County Zoning & Planning overview and related GoCodebook pages: Solano County zoning & planning overview, Solano County Zoning, Solano County Development Standards, Solano County Parking, Solano County Design Review, Solano County Overlay Districts, California Building Standards Code, California ADU law

Sources

Retrieved passages

CBC § 28 (Chapter or) High relevance
Solano County Zoning Code (Chapter that) High relevance
Solano County Zoning Code (Section 1-17) High relevance
CBC § 10 (Chapter shall) High relevance
Solano County Zoning Code (Chapter 28) High relevance
Solano County Zoning Code (section shall) High relevance
Solano County Zoning Code (Chapter 28) Medium relevance
Solano County Zoning Code (Section 28.102) Medium relevance
Solano County Zoning Code (Chapter 28) High relevance
Solano County Zoning Code (Section 28.13.) High relevance
Solano County Zoning Code (Section 28.01) Medium relevance
Solano County Zoning Code (Chapter 28) Medium relevance
Solano County Zoning Code (Chapter 28) Medium relevance
Solano County Zoning Code (Article IV) Medium relevance

Cited sections

**§ 28.114 Nonconforming Uses** — Solano County Zoning Ordinance (Nonconforming rules: continuance, repairs, destruction threshold, abandonment, zoning clearance, exceptions). (§ 28.114)
**§ 28.22.20 Suisun Marsh Agricultural District** (nonconforming uses inside Suisun Marsh; marsh development permit requirements; footprint limitation). (§ 28.22.20)
**§ 28.72** (Residential uses; secondary dwellings, guest house, conversion/size and setback rules tied to nonconforming status). (§ 28.72)
**§ 28.71.30** (Animal facilities — Small/Medium/Large standards; grandfathering of confined animal facilities predating May 3, 2005). (§ 28.71.30)
**§ 28.104** (Marsh Development Permit — required process for Suisun Marsh modifications). (§ 28.104)
Solano County Zoning & Planning overview and related GoCodebook pages: Solano County zoning & planning overview, Solano County Zoning, Solano County Development Standards, Solano County Parking, Solano County Design Review, Solano County Overlay Districts, California Building Standards Code, California ADU law
SolanoCounty_ZoningCode.md

Frequently asked questions

What is a nonconforming use in unincorporated Solano County?

A nonconforming use is any lot, building, structure, or land use that was lawfully established before a zoning change but that does not meet current rules. The county’s rules for these are laid out in § 28.114 (continuance, repair, abandonment, rebuilding limits).

Can I expand a nonconforming business or building?

Generally no — the ordinance prohibits enlargement, increase, or extension of a nonconforming use beyond the area it occupied when it became nonconforming, except where a specific district rule or exception allows it (for example, limited Suisun Marsh exceptions). § 28.114(C) and § 28.22.20(F).

If my nonconforming structure is damaged, can I rebuild it?

If damage exceeds 60% of the structure’s assessed value, the rebuilt structure must comply with current zoning and loses nonconforming status; for lesser damage, limited rebuilding is allowed subject to the code’s repair and expansion rules. § 28.114(C)(2).

How long can a nonconforming use sit idle before I lose it?

If the actual operation ceases for six months continuously, the county presumes abandonment and your site must thereafter comply with current zoning. Owners can rebut the presumption with proof. § 28.114(F).

I have an older guest house on my lot — can I convert it into a secondary dwelling or ADU?

Possibly. Guest houses and pre‑existing secondary dwellings are treated as legal nonconforming in some districts if they meet the district-specific date cutoffs; conversions to secondary dwellings or ADUs are allowed under the conditions in § 28.72 and subject to § 28.114 and applicable permitting. Verify eligibility and required approvals before permitting work.

Does the Suisun Marsh allow more flexibility for nonconforming uses?

Yes — uses established before 1977 in the Suisun Marsh are nonconforming but may undergo non‑substantial changes or additions inside the existing footprint with a marsh development permit under § 28.104; the footprint itself cannot be expanded. § 28.22.20(F).

My confined animal facility predates 2005. Can I expand it?

Facilities legally established prior to May 3, 2005 may be grandfathered as nonconforming but are not allowed to expand (in animals or developed area) unless they meet current standards for setbacks, water protection, and other listed requirements in § 28.71.30. Check the facility’s establishment date and proposed changes against those standards.

Do I need a zoning clearance before applying for a building permit on a nonconforming property?

Yes — the Director must issue a zoning clearance that states the extent of nonconformity and allowable repair/alteration before the county issues building, grading, well, septic, or business permits affecting a nonconforming use. § 28.114(G).

If the county approves a new use permit for my site, what happens to existing grandfathered rights?

Approval of a use permit for a use that had been operating as a nonconforming use will supersede and extinguish any prior grandfathered rights to continue the former nonconforming use; the new permit’s conditions then govern. § 28.114(E) and § 28.106.

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