Local zoning · Larkspur

Larkspur — Nonconforming Uses

Q: Can I change windows or deck placement on a nonconforming house in R‑1?

In R‑1 and T‑R , reconstruction or repair that involves changes to exterior openings (doors/windows), decks, or roof height is allowed only with an exception permit ; otherwise you may rebuild to the original openings if you can document them § 18.68.020(B)(1)(c) .

Q: If my nonconforming building was 75% damaged, can I rebuild it as it was?

Outside R‑1 / T‑R , restoration after damage is allowed only if the cost does not exceed 60% of the current replacement cost; if it exceeds 60% the structure generally must be brought into conformity (or otherwise authorized by permit). In R‑1 / T‑R , rebuilding to the original footprint is allowed subject to documentation and time limits § 18.68.020(B)(1–2) .

Q: If my R‑1 duplex wants a small addition, is any expansion allowed?

In R‑1 and T‑R , duplexes and multiple‑family dwelling groups may expand by up to 100 square feet per dwelling unit , attached to the existing dwelling, and such expansion requires an exception permit and must comply with other zoning rules § 18.68.020(D)(2) .

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

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Last reviewed: July 2, 2026

Overview

This page explains how the City of Larkspur treats nonconforming uses, nonconforming structures, and nonconforming lots under the City’s zoning code (Title 18). It summarizes what you can repair, rebuild, expand, or lose; special rules for R-1 and T‑R residential zones; and historic‑resource exceptions. For related procedural topics see the city’s pages on Larkspur Zoning, Larkspur Development Standards, Larkspur Design Review, Larkspur ADUs, Larkspur Parking, Larkspur Overlay Districts, and the California Building Standards Code where building/permitting technical standards live. All operational rules below are grounded in the Larkspur Municipal Code; see the Source References at the end for the controlling sections.

Chapter 18.68 is the city’s dedicated chapter on nonconformities; its purpose statement and definitions set the framework for the standards summarized here § 18.68.010 and § 18.68.015 .

Key rules (plain summary of the ordinance)

Interior repairs and routine maintenance to bring a lawfully existing building up to code are allowed without triggering conformity requirements; exterior work is limited unless special permits are obtained § 18.68.020(A) .
The City measures the scope of exterior work against the structure’s current replacement value. If work exceeds 60% of that value (as calculated by the City Chief Building Official using ICC valuation data), an exception or other discretionary permit is required § 18.68.020(A)(2–3) .
If a nonconforming use or structure is abandoned or discontinued for 180 continuous days, the right to the nonconforming use ends and any subsequent use must conform to the Code § 18.68.020(E) .
For damage/destruction, different rules apply in R‑1/T‑R vs. other zones. In R‑1/T‑R reconstruction to the original footprint and envelope is allowed subject to documentation and a two‑year start limit; outside those zones restoration may be limited by the 60% threshold § 18.68.020(B) .
Nonresidential (and non‑R‑1/T‑R) nonconforming uses generally may not be enlarged, relocated, or expanded beyond the area they occupied when they became nonconforming unless a use permit is approved; the Planning Commission must also make additional findings (including the findings in § 18.76.050) § 18.68.020(D) .
Special historic‑resource relief exists: residential historic structures on the City’s inventory can use a historic rehabilitation permit to maintain or modestly extend nonconforming features and may be allowed work beyond the 60% threshold under that permit § 18.68.035 .

District-by-district breakdown

Note: Larkspur’s zoning chapters list many districts citywide. The nonconforming rules in Chapter 18.68 apply city-wide but contain specific carve‑outs for certain districts (especially R‑1 and T‑R). Where the code below references a district it is because the ordinance text does so; where district numeric/metric standards are not in the nonconforming chapter they must be read in the specific district chapter (verify with the jurisdiction) .

R-1 (First Residential) — applicability to nonconformities

Purpose and where it applies: The R‑1 district is Larkspur’s single‑family residential district (see the district chapter for full purpose language). The nonconforming chapter specifically treats R‑1 as a residential zone with relaxed reconstruction rules after damage § 18.68.020(B)(1) .
Typical permitted uses (summary from zoning chapter): primarily single‑family dwellings; accessory uses as allowed in the R‑1 chapter (see district chapter; not repeated verbatim here).
Key dimensional standards relevant to nonconformities: reconstruction to the original footprint, envelope, floor area, and exterior door/window/deck placement is allowed if documentation exists; reconstruction work that changes openings, decks, or roof height requires an exception permit § 18.68.020(B)(1)(a–c) .
Special rules: post‑damage reconstruction must commence within 2 years; Planning Commission may grant a one‑year extension § 18.68.020(B)(1)(d) .

T-R (Two‑Unit Residential) — applicability to nonconformities

Purpose and where it applies: T‑R covers two‑unit residential settings; the nonconforming chapter treats T‑R similarly to R‑1 for damage/reconstruction rules § 18.68.020(B)(1) .
Typical permitted uses: duplex and other two‑unit residential uses (consult the T‑R chapter for the full list).
Key dimensional standards relevant to nonconformities: same reconstruction allowances as R‑1; limited by documentation and exception permit requirements for material changes § 18.68.020(B)(1) .
Special rule: In R‑1 and T‑R, duplexes/multifamily/dwelling groups may expand by up to 100 sq ft per dwelling unit, subject to an exception permit and zoning compliance § 18.68.020(D)(2) .

TD (Transit/ Downtown) — illustrative development standards that intersect with nonconformity rules

Purpose/where it applies: TD district development standards are set in Chapter 18.45 (Transit/Downtown); several TD provisions state that properties exceeding a district FAR on the code’s effective date “shall not be considered nonconforming” for certain rebuilding scenarios and provide reconstruction allowances when destroyed — see § 18.45.070 for FAR and reconstruction language .
Typical uses: mixed commercial/residential downtown uses (see Chapter 18.45).
Key numeric standards: FAR caps (e.g., 0.40 FAR in portions of TD); specific reconstruction rules for buildings damaged or destroyed (original gross square footage cannot be exceeded; reconstruction must meet other code requirements and commence within five years unless extended) § 18.45.070 .
How this intersects nonconformity rules: TD establishes that some pre‑existing exceedances are not treated as nonconforming for reconstruction if the reconstructed building does not exceed the original and if discretionary approvals and timelines are met § 18.45.070 .

SD (Special / Specific Downtown) — where it applies

Purpose and uses: Chapter 18.41 contains SD district standards (see that chapter). The SD chapter similarly provides that properties exceeding numeric standards on the effective date shall not automatically be nonconforming and sets reconstruction and discretionary review rules § 18.41.070 .
Key dimensional standards relevant to nonconformity: FAR limits in SD are set and the reconstruction rules parallel the TD approach (original gross square footage limits, review/permit requirements and time windows) § 18.41.070 .

OS (Open Space) and P‑D (Planned Development)

Purpose and where it applies: OS and P‑D chapters describe allowed uses and conditional uses. For P‑D, legally established uses at the time of P‑D establishment are explicitly treated as legal nonconforming uses and are subject to Chapter 18.68 rules § 18.55.040(C) . OS conditional uses are governed by the OS chapter’s use permit rules § 18.49.030 .
Key nonconformity interaction: when a district chapter declares that certain preexisting conditions are not treated as nonconforming or provides reconstruction timelines, both chapter‑level and Chapter 18.68 rules apply; always read both chapters together (verify with the jurisdiction) .

Table — Decision‑relevant nonconforming standards at a glance

Issue / Activity	What Larkspur’s code allows or requires	Code Reference
Interior repairs (nonconforming structures)	Building permit allowed for interior repair/maintenance regardless of where located in structure	§ 18.68.020(A)(1)
Exterior repairs/improvements (minor)	Allowed if no changes to exterior openings/decks/roof height AND cost ≤ 60% of current replacement value (City CBO uses ICC values)	§ 18.68.020(A)(2–3)
When an exception permit is required	Exterior openings change, decks/roof height change, OR cost > 60% replacement value	§ 18.68.020(A)(3)
Reconstruction after damage — R‑1 / T‑R	May rebuild to original footprint/envelope/openings if documented; must start within 2 years (1‑year extension possible)	§ 18.68.020(B)(1)(a–d)
Reconstruction after damage — other zones	Restoration allowed only if cost ≤ 60% of replacement cost; otherwise must conform	§ 18.68.020(B)(2)
Expansion / relocation of nonresidential nonconforming uses	Not allowed to expand/relocate to occupy more area unless a use permit is granted and additional findings (including § 18.76.050 findings) are met	§ 18.68.020(D)(1)
Small expansion for residential multi‑unit in R‑1/T‑R	Up to 100 sq ft per unit, attached to existing dwelling; exception permit required	§ 18.68.020(D)(2)
Abandonment / loss of nonconforming status	Continuous discontinuation/abandonment for 180 days causes loss of nonconforming right	§ 18.68.020(E)
Historic residential exceptions	Historic rehab permit can authorize maintenance or minor additions and waive the 60% threshold in specific cases	§ 18.68.035

Checklist (what an applicant must satisfy to proceed with work affecting a nonconforming building/use)

Confirm whether the affected building/use is a nonconforming structure or nonconforming use under § 18.08.600 / § 18.08.630 and Chapter 18.68 .
For exterior work: obtain an initial cost valuation or estimate to determine whether proposed work is ≤ 60% of current replacement cost as calculated by the City Chief Building Official (ICC data) § 18.68.020(A)(2–3) .
If work changes exterior openings, decks, or roof height, or cost > 60% — prepare an exception permit application per § 18.68.040 and the exception permit procedures § 18.68.040 and related procedural sections § 18.76.050 for use permit findings as applicable .
If restoring after damage in R‑1/T‑R: assemble documentation (photos/blueprints) substantiating original footprint and start reconstruction within 2 years; request extension from Planning Commission if needed § 18.68.020(B)(1)(a,d) .
If the site contains a historic resource on the City inventory and work would otherwise trigger conformity, evaluate a historic rehabilitation permit under § 18.68.035 .
If you propose to expand a nonresidential nonconforming use beyond its previous footprint or to relocate it, prepare a use permit package and supporting findings (Planning Commission review required) § 18.68.020(D)(1) .
Coordinate required reviews: design review or Larkspur Design Review as applicable (design review timelines and bonding are in design review chapter) § 18.64 .
Check ADU rules: ADU approvals interact with nonconforming setbacks and density rules; the ADU chapter states that no modification of nonconforming setbacks shall be required as a condition for ADU approval § 18.23.060 (ADU rules) .

Risks & Ambiguities

Issue	Why it matters	What to verify
Whether a pre‑existing numeric exceedance is treated as “nonconforming”	Some district chapters (e.g., TD, SD) state that certain pre‑existing exceedances are not treated as nonconforming for reconstruction — outcome affects entitlement and reconstruction options	Check the specific district chapter (e.g., § 18.45.070, § 18.41.070) and coordinate with Planning to confirm status
How the 60% replacement‑value test is calculated	The threshold determines whether an exception permit or full conformity is required; the City CBO uses ICC values with regional modifier	Verify the City Chief Building Official’s current method and valuation tables; request a written determination § 18.68.020(A)(2–3)
What constitutes “abandonment” or “discontinuation”	Loss of nonconforming rights after 180 days is triggered by abandonment/discontinuation — factual intent questions can arise	Collect occupancy, utility, lease, and maintenance records to document continuous use status; consult Planning for enforcement practice § 18.68.020(E)
Scope of allowable changes after damage in non‑R‑1/T‑R zones	Outside residential zones, reconstruction above 60% may be disallowed unless made conforming	Obtain cost estimates and talk to the Building Division early to determine restorability rules under § 18.68.020(B)(2)
Interaction with ADU rules	ADU approvals are ministerial and ADUs are generally exempt from many local development standards; ADU work may nevertheless interact with nonconforming conditions	ADU chapter clarifies that nonconforming setback modifications are not required as an ADU condition; verify ADU specifics under § 18.23.050–060
Historic resource allowances vs. design review	A historic rehabilitation permit can allow maintenance of nonconforming historic features, but design review and historic preservation standards may still apply	If the building is on the inventory, pursue § 18.68.035 relief and coordinate with the Historic Preservation program and Larkspur Historic Preservation (not all details are in Chapter 18.68)

Plain‑English Summary

If your Larkspur building or use legally predates a zoning rule, you can usually keep it and do interior repairs; limited exterior repairs are allowed without changing the nonconforming status, but bigger exterior work (or rebuilding that exceeds 60% of replacement cost) typically requires discretionary approval. Residential properties in R‑1 and T‑R get more flexibility to rebuild to their original footprint after damage, and historic homes have an additional rehab path — always get a City valuation and early Planning review to confirm the correct permit path § 18.68.020, § 18.68.035 .

Information Gaps

Full dimensional standards (specific front/side/rear setbacks, lot coverage, and FAR) for R‑1, T‑R, and other districts are in each district chapter (e.g., Chapters 18.20, 18.22, etc.) but were not reproduced in the retrieved nonconforming chapter excerpts. Verify district‑level numeric standards in the applicable chapter (not found in retrieved materials).
Specific language of § 18.76.050 (the use permit findings referenced for granting expansion of a nonconforming use) is cited by Chapter 18.68 but the full text of § 18.76.050 was not included in the search snippets above; consult the Use Permit chapter to review the findings in full (verify with the jurisdiction).
Practical processing timelines/fees for exception permits, historic rehabilitation permits, and Planning Commission hearings are in other procedural sections not fully reproduced here; consult Planning staff for application checklists (not found in retrieved materials beyond references) .

Source References

Larkspur Municipal Code Chapter 18.68, Nonconforming Uses and Structures — purpose, definitions, development standards, exception/historic rules § 18.68.010; § 18.68.015; § 18.68.020; § 18.68.035 .
Definitions of “Structure, Nonconforming” and “Use, Nonconforming” § 18.08.600; § 18.08.630 .
Reconstruction and FAR/reconstruction provisions in the TD district (Chapter 18.45) § 18.45.070 (reconstruction allowances and FAR rules) .
Reconstruction and FAR/reconstruction provisions in the SD district (Chapter 18.41) § 18.41.070 .
Planned Development (P‑D) district treatment of existing legal uses and cross‑reference to Chapter 18.68 § 18.55.040(C) .
ADU rules and interaction with nonconforming setbacks (Chapter 18.23) § 18.23.050–060 — specifically the statement that “No modification of nonconforming setbacks shall be required as a condition of ADU application approval” § 18.23.060 .
Design review timing and permit completion requirements (Chapter 18.64) § 18.64.090–100 (design review expiration and fees) .
Note: The Larkspur Municipal Code provided to this analysis is current through Ordinance 1096 (Feb. 4, 2026) as shown in the file excerpts .

Sources

Retrieved passages

Larkspur Zoning Code (Section 18.76.050) High relevance
Larkspur Zoning Code (Section 18.68.035) High relevance
Larkspur Zoning Code (Title 20) High relevance
Larkspur Zoning Code (Title 18) High relevance
Larkspur Zoning Code (§ 2) High relevance
Larkspur Zoning Code (Chapter 18.68) High relevance
Larkspur Zoning Code (Section 18.76.050) High relevance
Larkspur Zoning Code (Title 18) High relevance

Cited sections

Official Larkspur code library

Frequently asked questions

What happens if my nonconforming commercial business shuts down for a while — when is the right lost?

If a nonconforming use is abandoned or discontinued for a continuous period of 180 days, the nonconforming right ends and any subsequent use of the land or building must conform to the Code § 18.68.020(E) .

Can I change windows or deck placement on a nonconforming house in R‑1?

In R‑1 and T‑R, reconstruction or repair that involves changes to exterior openings (doors/windows), decks, or roof height is allowed only with an exception permit; otherwise you may rebuild to the original openings if you can document them § 18.68.020(B)(1)(c) .

If my nonconforming building was 75% damaged, can I rebuild it as it was?

Outside R‑1/T‑R, restoration after damage is allowed only if the cost does not exceed 60% of the current replacement cost; if it exceeds 60% the structure generally must be brought into conformity (or otherwise authorized by permit). In R‑1/T‑R, rebuilding to the original footprint is allowed subject to documentation and time limits § 18.68.020(B)(1–2) .

Can a nonconforming retail use expand into neighboring space in my building?

In zones other than residential, a nonconforming use or structure may not be relocated or enlarged to occupy a greater area than it did when it became nonconforming unless the Planning Commission grants a use permit and the additional findings (including § 18.76.050 findings) are met § 18.68.020(D)(1) .

Are ADUs affected by nonconforming setbacks?

The ADU chapter states that no modification of nonconforming setbacks shall be required as a condition of approving an ADU application, but ADUs must comply with state ADU law and building code; coordinate ADU permit review with the Building Division § 18.23.060 .

My house is on Larkspur’s historic resources inventory — does that change nonconforming rules?

Yes. For residential historic structures on the inventory, a historic rehabilitation permit can authorize repair, restoration, and minor additions that maintain (but cannot exacerbate) existing nonconformities; in some cases the historic rehab permit can permit work that would otherwise be barred by the 60% replacement‑value rule § 18.68.035 .

How does the City determine the “60% replacement value” threshold?

The threshold is measured using the City Chief Building Official’s determination of current replacement value, using the most recent ICC assessed valuation data with a regional modifier; ask the Building Division for the current valuation tables and written determination § 18.68.020(A)(2–3) .

If my R‑1 duplex wants a small addition, is any expansion allowed?

In R‑1 and T‑R, duplexes and multiple‑family dwelling groups may expand by up to 100 square feet per dwelling unit, attached to the existing dwelling, and such expansion requires an exception permit and must comply with other zoning rules § 18.68.020(D)(2) .

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