Local zoning · San Dimas

San Dimas — Nonconforming Uses

Nonconforming Uses under the San Dimas local zoning and planning code, with the controlling citations.

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Last reviewed: July 2, 2026

Overview

San Dimas treats nonconforming uses, structures and lots as legacy conditions that may continue in place but generally may not be expanded; the rules are administered through automatic variances, repair/abandonment limits, and specific discontinuance/amortization schedules. The controlling general rule is in § 18.204.170, with definitions in Chapter 18.08 and glosses for residential vs. commercial treatment in § 18.35.080 and § 18.35.090; specialized rules for signs, donation boxes and certain facilities appear in separate chapters. See the city's zoning summary for context at the San Dimas zoning & planning overview and read development standards before proposing changes to a nonconforming condition. § 18.204.170 ; § 18.08.340 ; § 18.35.080 .

How to use this page

  • Use the district-by-district subsections below to locate the local zone name that applies to your parcel and the specific nonconforming constraints that apply there.
  • When you see words like parking, design review, development standards, overlays, or ADUs in the text they link to the San Dimas menu pages which the city uses to explain review steps and standards. Plan to confirm parcel-specific facts with the Community Development Department.

Citywide rules you must know (short list)

  • Continued lawful existing uses are allowed by an automatic variance but the use may not be expanded or enlarged except in very limited circumstances — see § 18.204.170. § 18.204.170 .
  • Repair threshold: repairs in a 12-month period exceeding 50% of the building's value trigger full conformance to current code for the rebuilt portion — § 18.204.150. § 18.204.150 .
  • Abandonment: if a nonconforming use ceases for one year (or other specific amortization periods listed), the automatic variance ends — § 18.204.160 and the amortization breakdown in § 18.204.170(B). § 18.204.160 ; § 18.204.170(B) .
  • Residential/noncommercial exceptions: many residential and noncommercial improvements have separate, more-permissive repair/rebuild allowances — § 18.35.080. § 18.35.080 .
  • Some use types have tailored discontinuance windows (e.g., donation boxes, non-US mailboxes) and notice/appeal procedures — § 18.198.050. § 18.198.050 .
  • Signs are separately amortized and may be removed on a schedule — § 18.152.080. § 18.152.080 .

District-by-district breakdown (where nonconforming rules appear in zone text)

Note: each district subsection below summarizes the zone purpose and the code excerpts that control nonconforming treatment for that district. Where the chapter uses a more general rule, that is cited (often § 18.204.170) and supplemented by zone-specific notes.

SF-H (Single‑Family Hillside) — purpose & where it applies

  • Purpose: hillside single‑family development standards for safety, scenic preservation and slope‑sensitive design; applies inside mapped hillside areas (see Chapter 18.32) § 18.32.010 .
  • Typical permitted uses: detached single‑family homes, accessory uses, limited home occupations per the residential rules in Title 18. § 18.32.010 .
  • Key dimensional standards: slope‑sensitive lot area, setbacks and lot width rules appear throughout the specific hillside chapter; consult San Dimas Development Standards for exact figures. § 18.32.020 .
  • Nonconforming specifics: existing residential improvements built legally at the time of construction may be maintained, repaired and in many cases enlarged under the residential nonconforming provisions without triggering full compliance with later development standards — see § 18.35.080 (residential/noncommercial improvements may be repaired, remodeled and enlarged subject to limits) and the general nonconforming rules § 18.204.170. § 18.35.080 ; § 18.204.170 .

R‑1 / Single‑Family (typical) — purpose & where it applies

  • Purpose: provide for single‑family detached neighborhoods; see the single‑family development chapters (e.g., § 18.24 and related) for setbacks and lot coverage. § 18.24.050 .
  • Typical permitted uses: single‑family residences, accessory buildings, home occupations. § 18.24 excerpts .
  • Key dimensional standards: front, side and rear setbacks, and maximum lot coverage; when rebuilding nonconforming residential structures, maximum rebuilt lot coverage shall not exceed 35% and one-time increases are limited to 10% or up to 35% total where allowed — § 18.35.080(C)(3). § 18.35.080(C)(3) .
  • Nonconforming specifics: residential nonconformities are treated more leniently (repairs, one-time lot coverage increase, rebuild after catastrophe subject to review) — see § 18.35.080 and general rules § 18.204.170. § 18.35.080 ; § 18.204.170 .

Creative Growth Zone — Area 3 (Downtown mixed‑use) — purpose & where it applies

  • Purpose: downtown mixed‑use corridor; encourages retail, office, service, live/work and compatible residential to blend with historic fabric — § 18.140.090 (Area 3). § 18.140.090 .
  • Typical permitted uses: retail, eating places (no drive‑through), live/work, multifamily (sub‑areas vary). § 18.140.090(3)(a–d) .
  • Key dimensional standards: building height and setbacks often determined by review authority (Chapter 18.12); parking rules are specific to Area 3 (garage space and guest/extra‑bedroom parking schedules) — consult the development standards and parking page. § 18.140.090(6) .
  • Nonconforming specifics: “There shall be no extension, expansion or enlargement of an existing nonconforming use, nor the addition of structures or other facilities in conjunction with such existing use” — Area 3 and other specific plan chapters point to the citywide continuation rule § 18.204.170 for details. § 18.140.090(8) ; § 18.204.170 .

Area 4 — Commercial / Light Industrial (Creative Growth / Specific Plan contexts)

  • Purpose: light industrial and commercial employment uses where allowed (Area 4 text in the Creative Growth and certain specific plans) — § 18.140.090(B) .
  • Typical permitted uses: M‑1 uses plus retail/service, offices; conditional use lists cross‑refer to M‑1 zone. § 18.140.090(B)(1–3) .
  • Key dimensional standards: as set in the specific plan and the applicable development standards (setbacks, heights, parking) — see the specific plan exhibit pages and the city’s development standards. § 18.140.100 referenced in chapter text .
  • Nonconforming specifics: no expansion of nonconforming uses is allowed; destroyed nonconforming commercial structures may have restrictive reestablishment rules (see § 18.35.090 requiring reestablishment as residential in certain destruction cases). § 18.140.090(8) ; § 18.35.090 .

Downtown Specific Plan / Other Specific Plans (No. 17, 20, 24, 26, etc.)

  • Purpose & where it applies: each Specific Plan chapter sets tailored permitted uses, dimensional standards and references the municipal code for matters the plan doesn’t cover (e.g., § 18.540.040 for Specific Plan No. 24). § 18.540.040 .
  • Nonconforming specifics: specific plans commonly state that uses made nonconforming by plan adoption “may be continued in accordance with § 18.204.170” and prohibit expansion of nonconforming uses — see Specific Plan provisions across Title 18. § 18.532.010 and many specific plan sections reference § 18.204.170 ; § 18.540.040(D) .

Key code excerpts (decision‑relevant) — quick reference table

What it controls Short rule Code reference
Continuance but no expansion of existing uses Existing lawful uses may continue by automatic variance but may not be enlarged/extended except narrow exceptions § 18.204.170(A)
Repair threshold (trigger to conform) Repairs >50% of value in 12 months require rebuilding to current code § 18.204.150
Abandonment / lapse Nonconforming variance ends if use suspended/ceases for 1 consecutive year (or other amortization periods) § 18.204.160 and § 18.204.170(B)
Residential exceptions (repairs, rebuilding) Residential/noncommercial improvements get leniency: repairs, one-time lot coverage increase up to 35% with conditions § 18.35.080
Lot defined as nonconforming A “nonconforming lot” is a legally created pre‑ordinance lot that doesn’t meet current lot area/width (min. 6,500 sq ft described) § 18.08.340
Donation boxes / small collection facilities Treated as nonconforming if they don’t meet locational/development standards; may be discontinued within one year after notice, with appeals/extensions available § 18.198.050
Sign amortization/removal Some existing signs allowed to continue until significantly altered or amortized—city may require removal under schedule § 18.152.080

Checklist (what an applicant / property owner must satisfy to keep or alter a nonconforming situation)

  • Confirm whether the use/structure was lawfully established before the zoning/amendment that made it nonconforming (collect deeds, permits and dated evidence) — verify under § 18.204.170. § 18.204.170 .
  • Determine classification: nonconforming use, nonconforming building, nonconforming lot — see § 18.08.340 (nonconforming lot) and the definitions in Chapter 18.08. § 18.08.340 .
  • If planning repairs/alteration, calculate repair value vs. 50% threshold; if above, plan to bring rebuilt portion into conformance — § 18.204.150. § 18.204.150 .
  • If the director notifies the use as nonconforming, note appeal deadlines: 30 days for appeals and 6 months before abatement to apply for extension — § 18.198.050(C–D). § 18.198.050 .
  • If seeking an extension of a discontinuance date, file the extension application on city forms and prepare evidence addressing the commission’s factors (investment, salvage value, neighborhood compatibility, etc.) — § 18.198.050(D). § 18.198.050(D) .
  • If proposing to change a nonconforming commercial use to a lawful use or to build on a nonconforming lot, consult the applicable specific plan or zone standards and the development‑plan review/Design Review process — see § 18.12 (Design Review) and the local development standard chapter. § 18.12.030 .
  • Confirm parking impacts and whether special parking rules apply to the zone or to ADUs — consult the city's parking page when developing site plans. Chapter 18.156 and specific plan parking subsections .

(Where the checklist references “parking” or “design review” above, see the linked San Dimas menu pages for step‑by‑step permit information: parking, design review, development standards, overlay districts, ADUs, and building codes.)

Risks & Ambiguities

Issue Why it matters What to verify
Was the original use “lawful” at time of establishment? Only lawfully established uses may continue under the automatic variance; if not lawful, continuance may be denied Confirm permits, dated leases, business registrations; cite § 18.204.170(A)
Repairs vs. rebuild threshold (50%) If repairs exceed 50% of value in a 12‑month period, current standards apply — can force costly upgrades Obtain contractor estimates and a qualified valuation before starting work; see § 18.204.150
Abandonment / amortization periods Some uses (livestock, outdoor advertising) have specific amortization or time windows that terminate rights after a set time Verify whether an amortization timetable applies under § 18.204.170(B) and any zone‑specific clauses
Residential/noncommercial carveouts Residential nonconforming rules are more permissive — misclassifying a use can change available options dramatically Confirm whether your structure/use qualifies as “noncommercial” under § 18.35.080
Parcel-specific overlay or specific plan rules Specific plans or overlays may impose their own nonconforming limitations (sometimes stricter) Check the applicable Specific Plan chapter (e.g., § 18.540, § 18.528) and overlay rules — Verify with the jurisdiction
Sign and accessory equipment rules Signs or accessory donation boxes can be amortized separately or treated as nuisances, requiring removal Check § 18.152.080 for sign amortization and § 18.198.050 for donation boxes

Plain‑English Summary

If your San Dimas building or use was legal when it started but no longer matches today's zoning, it is probably a "nonconforming" use or structure and generally can stay — but you usually cannot expand it, and big repairs or long periods of nonoperation can force it to be removed or rebuilt to current standards. See § 18.204.170 for the main rule and § 18.35.080 for how residential properties are handled. § 18.204.170 ; § 18.35.080 .

Source References

  • § 18.204.170 (Nonconforming uses — automatic variance; limitations; amortization)
  • § 18.204.150 (Repairs threshold: 50% rule)
  • § 18.204.160 (Abandonment / lapse of variance)
  • § 18.35.080 (Provisions for existing residential and noncommercial improvements)
  • § 18.35.090 (Nonconforming commercial structures destroyed — reestablish rules)
  • § 18.08.340 (Definition: Lot, nonconforming)
  • § 18.198.050 (Discontinuance rules & notice/appeal for small collection/donation boxes)
  • § 18.152.080 (Nonconforming signs / amortization)
  • Chapter 18.12 (Design/Development plan review procedures) — § 18.12.030 for submittal requirements
  • Specific plan examples: § 18.140.090 (Creative Growth Zone / Area 3) ; § 18.540.040 (Specific Plan No. 24 general notes)

Sources

Retrieved passages

  • CBC § 1967 (chapter so) High relevance
  • San Dimas Zoning Code (chapter or) High relevance
  • San Dimas Zoning Code High relevance
  • San Dimas Zoning Code (§ 18.198.040.) High relevance
  • San Dimas Zoning Code (chapter are) High relevance
  • CBC § 1967 (chapter any) High relevance
  • San Dimas Zoning Code (§ 2) High relevance
  • San Dimas Zoning Code (§ 18.198.040.) Medium relevance
  • San Dimas Zoning Code High relevance
  • San Dimas Zoning Code Medium relevance
  • San Dimas Zoning Code (§ 66314) Medium relevance
  • San Dimas Zoning Code (§ 280.05) Medium relevance
  • San Dimas Zoning Code (§ 66333) Medium relevance
  • CBC § 1 (§ 1) Medium relevance
  • San Dimas Zoning Code Medium relevance
  • San Dimas Zoning Code Medium relevance
  • San Dimas Zoning Code (§ 1) Medium relevance
  • CPC § 1 (§ 1) Medium relevance
  • San Dimas Zoning Code (§ 1) Medium relevance
  • CPC § 1 (§ 1) Medium relevance
  • San Dimas Zoning Code (§ 795.6) Medium relevance
  • San Dimas Zoning Code (title includes) Medium relevance
  • San Dimas Zoning Code (§ 1) Medium relevance
  • CPC § 18.528.010 (Article I.) Medium relevance
  • San Dimas Zoning Code (§ 1) Medium relevance
  • San Dimas Zoning Code (§ 18.50.050.) Medium relevance
  • San Dimas Zoning Code (§ 1B) High relevance
  • San Dimas Zoning Code (§ 4) Medium relevance
  • San Dimas Zoning Code (section does) Medium relevance
  • San Dimas Zoning Code (chapter any) Medium relevance
  • San Dimas Zoning Code (§ 502.22) Medium relevance
  • San Dimas Zoning Code (§ 501.26) Medium relevance
  • San Dimas Zoning Code (chapter or) Medium relevance
  • San Dimas Zoning Code (section has) Medium relevance

Cited sections

Frequently asked questions

What exactly does San Dimas allow as a nonconforming use?

If a use was lawfully established before the current ordinance or map change, San Dimas allows it to continue under an automatic variance but it generally may not be expanded or enlarged; exceptions and time limits are listed in § 18.204.170. § 18.204.170

Can I rebuild a nonconforming house after a fire and increase its size?

Yes, but residential/noncommercial rebuilds are limited: rebuilt nonconforming residential structures may not exceed 35% lot coverage and may receive a one-time lot coverage increase of up to 10% (or up to 35%) under § 18.35.080; substantial repairs above the 50% threshold may require full conformance per § 18.204.150. § 18.35.080 ; § 18.204.150

If I stop operating a nonconforming business, can I restart it later?

Not always — the automatic variance ends if the use is suspended or discontinued for a consecutive period (commonly one year), and some uses have specific amortization windows (e.g., livestock, signage) listed in § 18.204.170(B). § 18.204.170(B)

Are there special rules for signs and donation boxes?

Yes. Signs have their own amortization and alteration rules (nonconforming signs may be allowed until "significantly altered") under § 18.152.080; donation boxes and similar collection facilities have a specific discontinuance schedule and notice/appeal process under § 18.198.050. § 18.152.080 ; § 18.198.050

Do nonconforming rules prevent me from building an ADU?

The San Dimas ADU chapter implements state ADU law; state rules limit a local agency’s ability to deny an ADU because of nonconforming zoning conditions. San Dimas refers ADU applicants to the ADU chapter and to Chapter 18.08 definitions; check § 18.38 and state ADU rules. § 18.38.010

Can I expand a nonconforming commercial use that’s been there for decades?

No — expansion or enlargement of a nonconforming use is generally prohibited (the city repeatedly states “no extension, expansion or enlargement”) and the general limit is in § 18.204.170 plus zone/specific plan clauses that restate the prohibition. § 18.204.170

Who decides whether something is nonconforming, and can I appeal?

The Director of Community Development may determine a use/building is nonconforming and must provide notice; the owner/operator/lessee has 30 days to appeal to the Planning Commission and may seek a one‑year extension of discontinuance under the Planning Commission’s public hearing process — see § 18.198.050(C–D). § 18.198.050(C–D)

What triggers a requirement to bring a nonconforming building up to current standards?

If repairs within any 12‑month period exceed 50% of the building’s value, the building must be made to conform to the current requirements for new buildings — § 18.204.150. § 18.204.150

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