Half Moon Bay — Nonconforming Uses

Last reviewed: July 2, 2026

Overview

This page explains how the City of Half Moon Bay treats nonconforming uses, nonconforming structures, and nonconforming lots under the City’s Title 18 (Zoning). The primary rules live in § 18.25.010–.100 (Chapter 18.25) with district‑specific rules in chapters such as § 18.06.070 (residential), § 18.07.050 (commercial), and § 18.12.035 (open space). Refer to the city’s development and design rules (setbacks, height, parking, and review processes) when evaluating changes to a nonconforming condition. § 18.25.010

(First time mentions of related topics are linked to the Half Moon Bay menu pages: see development standards, parking, design review, overlay districts, ADUs, California Building Standards Code, historic preservation, and variances and exceptions.)

Core rules (what the Title 18 ordinance actually says)

• Continuance but no extension: A lawful use, building, or structure that was lawful on January 2, 1964 may continue even if it does not conform, but it may not be extended to occupy a larger area than it occupied on that date; abandonment converts the parcel to conforming uses. § 18.25.010
• Abandonment standards: If a nonconforming use is wholly discontinued for one year it is conclusively presumed abandoned; a continuous discontinuance of six months also triggers limits on future uses of a building. § 18.25.015 and § 18.25.050
• Enlargement/prolongation: Enlargement, extension, reconstruction or structural alteration to increase a nonconforming use is prohibited except when the use is changed to a conforming use; ordinary maintenance and repairs up to 25% of assessed value in any 12‑month period are allowed. § 18.25.060
• Reconstruction after damage: If a nonconforming building is destroyed or damaged to the point that repair/reconstruction would cost more than 50% of assessed value, the building thereafter must meet current zoning rules; lesser damage may be repaired subject to limits on increasing nonconformity. § 18.25.070
• Time to file repairs/rebuild permits after catastrophe: For residential and commercial nonconforming buildings, a building permit to replace or repair must be filed within 24 months of the damaging event; any increased nonconforming encroachments are not allowed unless a variance/exception is approved. § 18.06.070 and § 18.07.050
• Special short deadlines / prohibitions for certain uses: Nonconforming auto wrecking and certain above-ground petroleum storage nonconforming uses must cease within two years unless a use permit or other approval is obtained. § 18.25.090 and § 18.25.100
• District‑specific rules can modify these basic principles (see below). Chapter 18.25 overall applies the rules in a city‑wide framework. § 18.25.010

District‑by‑district breakdown (purpose, typical permitted uses, key dimensional standards, and where it applies)

Notes: every district name and statutory standard below is bolded where used. Where the code gives detailed numbers we cite the specific §; where the specific numeric standard is not present in the retrieved excerpts we note that the numeric detail is Not found in retrieved materials and advise to verify with the jurisdiction.

R‑1, R‑2, R‑3 — Residential Districts

• Purpose and typical uses: R‑1, R‑2, R‑3 districts regulate single‑family, two‑family, and multi‑family residential uses respectively; see Chapter § 18.06.010–.030 for intent and the schedule of uses. § 18.06.010 and § 18.06.020
• Nonconforming rules: Residential nonconforming structures damaged by catastrophe may be rebuilt or repaired provided any nonconforming lot coverage, height, FAR or setback encroachments are not increased beyond pre‑damage conditions, unless a variance is approved; a building permit must be filed within 24 months. § 18.06.070
• Key dimensional standards (where the code provides them): The residential chapter references standard tables (Table B) and special tables for substandard and severely substandard lots (Tables E and F). Examples in those tables include heights such as 28 ft for two‑story and 20 ft for single‑story in the substandard‑lot table; consult § 18.06.030 and § 18.06.050 for full numeric tables. § 18.06.030 and § 18.06.050
• Where it applies: Citywide residential zones; nonconforming residential structures are also treated specially within open space reserve and urban reserve districts (see § 18.11.040). § 18.11.040

C‑D and C‑R — Downtown Commercial and Commercial‑Residential

• Purpose and typical uses: C‑D (downtown commercial) and C‑R (commercial‑residential) accommodate retail, commercial services, and mixed use downtown activity. See § 18.07.010–.030 for permitted uses and rules. § 18.07.020 and § 18.07.030
• Nonconforming rules: Existing nonconforming commercial structures may be repaired after catastrophe provided nonconforming height/setback encroachments are not increased and a permit is filed within 24 months; ordinary maintenance up to 25% of assessed value in a 12‑month period is allowed. § 18.07.050 and § 18.25.060
• Historic downtown: The historic downtown has additional protections; alterations or demolition of designated landmarks follow the historic resources ordinance and may be eligible for exceptions to development standards to preserve historic integrity. § 18.07.055
• Key dimensional standards: General development standards for the C districts are in § 18.07.030–.045 (minimum site area, frontage depth rules, and exceptions). Specific numeric setbacks/height must be read in those subsections; see § 18.07.030 for the general framework. § 18.07.030

OS‑A, OS‑P, OS‑C — Open Space (Active, Passive, Conservation)

• Purpose and typical uses: OS‑A, OS‑P, OS‑C preserve beaches, bluffs, parks, trails and sensitive habitats; commercial recreation uses are limited and new dwellings are prohibited. § 18.12.010 and § 18.12.040
• Nonconforming rules: Existing nonconforming structures (for example, state parks employee residences) may be repaired and maintained without a use permit provided no structural alteration increases floor area or unit count; changes are limited to maintenance and repair. § 18.12.035
• Key dimensional standards: Maximum structure height in these districts is 16 ft unless the planning commission grants a narrowly defined exception for certain public safety or public park facilities; setback rules include large buffers (100 ft from residential districts in many cases). § 18.12.025 and § 18.12.035

OS‑R and U‑R — Open Space Reserve and Urban Reserve

• Purpose and typical uses: OS‑R and U‑R protect reserve lands; new development and conversion to urban uses are tightly controlled. § 18.11.010–.035
• Nonconforming rules: Existing nonconforming residential structures in OS‑R and U‑R may be maintained, repaired, or remodeled but must conform to applicable R‑1 development standards (min lot size, setbacks, height, lot coverage, FAR). Procedures for use permits, exceptions and variances apply. § 18.11.040

A‑1 — Agricultural

• Purpose and typical uses: A‑1 facilitates primary agricultural uses and related accessory dwellings for farm help; see § 18.13.010–.020 for permitted uses. § 18.13.020
• Nonconforming rules: The agricultural chapter establishes permitted uses and development standards; the general nonconforming rules of Chapter 18.25 apply. Specific A‑1 nonconforming instructions beyond application of Chapter 18.25 are Not found in retrieved materials. Verify with the jurisdiction. § 18.25.010

Mobile home parks (Chapter 18.17)

• Nonconforming rules: Mobile home parks lawfully existing at ordinance effective date may continue as nonconforming uses but may not be extended to increase the number of spaces or occupy a larger area than at the effective date; they are subject to Chapter 18.25. § 18.17.050

Other districts (IND, P‑S, C‑VS, C‑G, PUD, etc.)

• Where specific nonconforming rules are present they are in the relevant chapter (for example § 18.08.050 addresses nonconforming structures in some commercial districts); otherwise the Chapter 18.25 rules are the baseline. Specific numeric standards for these districts are Not found in retrieved materials in the excerpts; consult the applicable chapter cited in Title 18 for the full standards. § 18.25.010

Quick decision table (most decision‑relevant standards / items)

Checklist — what an applicant must satisfy (preliminary)

• Confirm nonconforming status and the area occupied on January 2, 1964 (if relevant) — § 18.25.010.
• Determine whether the use or building has been discontinued for 6 months or 1 year (abandonment rules) — § 18.25.015 and § 18.25.050.
• If proposing repair after damage, calculate reconstruction cost as a % of current assessed value to check the 50% threshold — § 18.25.070.
• If repair/rebuild is needed, file required building permit within 24 months of the event — § 18.07.050 / § 18.06.070.
• Check whether the work would increase any nonconforming height, setback or lot‑coverage encroachment; if so, prepare a variance/exception application — § 18.25.060 and § 18.07.060.
• For downtown or historic district work, include design review materials and consider historic review criteria — § 18.07.055 and § 18.07.060.
• Verify parking impacts and whether a parking exception or additional parking is required for changes in use — consult § 18.07.030 & Chapter 18.36 on parking. parking
• If in an overlay district or coastal zone, check overlay rules and coastal permit rules — see overlay districts and Chapter 18.20 for coastal permit applicability.

Risks & Ambiguities

Plain‑English summary

If your building or use in Half Moon Bay predates a zoning change, you can often keep it, but you generally cannot make it bigger or more nonconforming; long‑term gaps in use, major destruction (over 50% of value), or failure to act within set deadlines (e.g., file a permit within 24 months) will usually force you to meet today’s zoning rules. § 18.25.010–.070 and district chapters govern the details.

Source References

• Half Moon Bay Zoning (Title 18), Chapter 18.25 Nonconforming Uses — § 18.25.010–.100. (Downloaded from https://ecode360.com/HA4470)
• Half Moon Bay Zoning, Residential Chapter — § 18.06.030, § 18.06.050, § 18.06.070 (development standards and nonconforming structures).
• Half Moon Bay Zoning, Commercial (C‑D, C‑R) — § 18.07.030, § 18.07.050, § 18.07.055, § 18.07.060.
• Half Moon Bay Zoning, Open Space — § 18.12.025 (specific development standards) and § 18.12.035 (nonconforming structures).
• Mobile home parks — § 18.17.050 (nonconforming uses continuation, limits).
• City Title 18 table of contents and cross references (Title 18 Index).

Retrieved passages

• Half Moon Bay Zoning Code (§ 18.25.015.) High relevance show source text
• Half Moon Bay Zoning Code (§ 18.24.090.) High relevance show source text
• CBC § 18.07.045 (§ 18.07.045) High relevance show source text
• Half Moon Bay Zoning Code (section shall) High relevance show source text
• Half Moon Bay Zoning Code (§ 18.25.050.) High relevance show source text
• CBC § 2 (§ 2) High relevance show source text
• Half Moon Bay Zoning Code (§ 18.25.070.) High relevance show source text
• Half Moon Bay Zoning Code (§ 18.40.050) High relevance show source text
• Half Moon Bay Zoning Code (§ 1) High relevance show source text
• Half Moon Bay Zoning Code (§ 18.17.060) High relevance show source text
• Half Moon Bay Zoning Code (§ 2) High relevance show source text
• Half Moon Bay Zoning Code (§ 18.04.030.) Medium relevance show source text
• Half Moon Bay Zoning Code (Title 18) Medium relevance show source text
• CBC § 66314 (§ 66314) Medium relevance show source text

Cited sections

• Half Moon Bay Zoning (Title 18), Chapter 18.25 **Nonconforming Uses** — **§ 18.25.010–.100**. (Downloaded from ) (Title 18)
• Half Moon Bay Zoning, **Residential** Chapter — **§ 18.06.030**, **§ 18.06.050**, **§ 18.06.070** (development standards and **nonconforming structures**). (§ 18.06.030)
• Half Moon Bay Zoning, **Commercial (C‑D, C‑R)** — **§ 18.07.030**, **§ 18.07.050**, **§ 18.07.055**, **§ 18.07.060**. (§ 18.07.030)
• Half Moon Bay Zoning, **Open Space** — **§ 18.12.025** (specific development standards) and **§ 18.12.035** (nonconforming structures). (§ 18.12.025)
• Mobile home parks — **§ 18.17.050** (nonconforming uses continuation, limits). (§ 18.17.050)
• City Title 18 table of contents and cross references (Title 18 Index). (Title 18)
• HalfMoonBay_ZoningCode.md
• 2025 California ADU handbook.md

• Official Half Moon Bay code library