Local zoning · Monte Sereno

Monte Sereno — Nonconforming Uses

Q: What happens if a nonconforming building is damaged by a storm or fire?

If repairing the damage would cost more than 75% of the structure’s assessed value, the right to maintain the nonconforming use/structure terminates; limited reconstruction is allowed if started timely and does not increase pre‑damage nonconforming features. § 10.07.040(D) ; § 10.07.070–.080

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

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Last reviewed: July 2, 2026

Overview

This page summarizes what the City of Monte Sereno zoning ordinance (Title 10 of the Monte Sereno Municipal Code) actually says about nonconforming uses, nonconforming structures, and nonconforming lots. It pulls the controlling local provisions (Chapter 10.07) and places them in the context of the City's zoning districts (R-1-44, R-1-20, R-1-8, RM, P, P/RM, PD) so you can see how nonconformity interacts with district rules and development standards. All requirements below are grounded in the Monte Sereno code; specific § citations and the retrieved ordinance file references are given inline.

What Monte Sereno's code says (chapter summary)

The City treats any lawful pre‑existing building or use that does not meet current zoning as nonconforming and allows continuation only subject to limits and termination rules in Chapter 10.07. § 10.07.010
A nonconforming use or structure generally cannot be enlarged or extended beyond the area it occupied when it became nonconforming. § 10.07.010
Ordinary maintenance is allowed but repair/maintenance spending is capped and floor area cannot be increased. § 10.07.030 (maintenance limits: 25% in any 12‑month period; no increase to the floor area that existed at the time the use became nonconforming)
Nonconforming uses terminate automatically in several circumstances (abandonment, vacancy >12 months, change to conforming use, violations), and there are long-stop dates for termination by operation of the Chapter. § 10.07.040 (including the 12‑month vacancy rule and the damage/destruction standard)
Nonconforming structures may be maintained and, in limited situations, reconstructed after damage — but restoration cannot increase nonconforming features or expand size/units beyond pre‑damage condition, and reconstruction deadlines (e.g., commence within six months) apply. § 10.07.050–.080

(See detailed district notes below for where nonconforming buildings interact with district development standards such as coverage, imperviousness, parking and design review. For district lists and base minimum lot sizes see § 10.05.010.) § 10.05.010

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

Note: the City’s zoning district list and the text below come from the Monte Sereno zoning chapters; each district entry cites the local code section(s) that define uses or standards.

R-1-44 (Forty‑three thousand five hundred sixty sq. ft. minimum)

Purpose: very-low-density single‑family residential (listed in § 10.05.020). § 10.05.020
Typical permitted uses: one single‑family dwelling, accessory structures, horticulture and limited home occupations (see § 10.05.020). § 10.05.020
Key dimensional/development standards: minimum lot area set by the district table in § 10.05.020; maximums on structural and impervious coverage and parking requirements are set in the residential rules that apply to R zones (see coverage/parking items in the residential regulations). § 10.05.020; coverage/parking rules in the residential development standards.
Where it applies: parcels designated R‑1‑44 on the official zoning map; nonconforming structures within this district are governed by Chapter 10.07 and by the R‑1‑44 development limits. § 10.07.010; § 10.05.020

R-1-20 (Twenty thousand sq. ft. minimum)

Purpose: low‑density residential; one single‑family dwelling per lot is the baseline. § 10.05.030
Typical permitted uses: one single‑family dwelling, accessory buildings, horticulture, limited animals and home occupations; Accessory Dwelling Units (ADUs) and Junior ADUs are explicitly allowed (see the ADU chapter). § 10.05.030; ADU rules in the accessory dwelling unit section.
Key dimensional standards: minimum lot size 20,000 sq ft (district designation), maximum structural coverage ~30% and impervious coverage ~40% in the R‑1‑20 framework; off‑street parking standards and building size limits appear in the same residential development rules. § 10.05.030 (coverage/impervious/parking provisions).
Where it applies: R‑1‑20 mapped parcels; any nonconforming condition must be judged under Chapter 10.07 in addition to the R‑1‑20 rules. § 10.07.010; § 10.05.030

R-1-8 (Eight thousand sq. ft. minimum)

Purpose: standard single‑family residential neighborhood district. § 10.05.040
Typical permitted uses: one single‑family dwelling, accessory buildings/structures, horticulture, limited animals, home occupations, ADUs and JADUs; some community uses allowed with a use permit. § 10.05.040
Key dimensional standards: minimum lot area 8,000 sq ft; maximum structural coverage 30% and impervious coverage 40% (subject to formula reductions by lot size and slope); parking minimums tied to on‑street parking availability. See § 10.05.040 for the enumerated coverage/parking rules that apply to R districts. § 10.05.040
Where it applies: R‑1‑8 mapped parcels and cluster/PD exceptions where allowed; nonconforming structures in R‑1‑8 are maintained/terminated per Chapter 10.07. § 10.07.010; § 10.05.040

RM (Multi‑Family Residential District)

Purpose: to allow small‑scale multi‑family forms where designated (RM). § 10.05.043
Typical permitted uses: single‑family, duplex, triplex, accessory buildings, limited animals and home occupations; development standards and coverage/parking rules specific to RM are in the RM subsection. § 10.05.043
Key dimensional standards: RM minimum lot area is stated in § 10.05.010 and coverage/parking limits are listed in the RM regulatory subsection; consult § 10.05.043 for the full list. § 10.05.010; § 10.05.043
Where it applies: parcels zoned RM; nonconforming uses/structures in RM are subject to Chapter 10.07 limits. § 10.07.010

P / P‑RM (Public and Public/Residential Multi‑Family)

Purpose: public uses and mixed public/residential where mapped. § 10.05.010 and P/P‑RM subsections.
Typical permitted uses: public facilities, and residential uses where P/RM allows them; see the district text for permitted uses. § 10.05.010
Key dimensional standards: these districts defer to development standards listed in Chapter 10.05 and any PD permits that overlay them. § 10.05.010
Where it applies: mapped public or mixed parcels; nonconforming conditions follow Chapter 10.07. § 10.07.010

PD (Planned Development)

Purpose: site‑specific alternative development standards adopted by PD permit; PD controls override base district rules where implemented. § 10.05.047
Typical permitted uses: uses and sizing are those specifically authorized in the PD permit (not the default base district once the PD is effectuated). § 10.05.047
Key dimensional standards: the PD permit lists exact heights, floor area, parking, and coverage; if a PD has not been effectuated the base district rules apply. § 10.05.047
Where it applies: parcels where a PD zoning ordinance and permit are in force; nonconformities on PD properties are judged against the PD permit and Chapter 10.07. § 10.05.047; § 10.07.010

Quick reference table — most decision‑relevant standards and code references

Topic / Standard	Value or rule (Monte Sereno)	Code Reference
Definition of nonconforming	Lawful pre‑existing building or use that does not conform to current district rules	§ 10.01.020 AL
Continue a nonconforming use/structure?	Permitted subject to limits; may not be enlarged beyond original nonconforming area	§ 10.07.010
Maintenance—spending cap	Ordinary maintenance allowed; cost of work ≤ 25% of the building's assessed value in any 12‑month period	§ 10.07.030
Vacancy/abandonment termination	Nonconforming use terminates after 12 consecutive months of non‑operation or vacancy	§ 10.07.040(B)(3–4)
Damage/destruction rule	If repair would exceed 75% of assessed value, nonconforming use/structure rights terminate	§ 10.07.040(D)
Long‑stop termination (by enactment)	Main building nonconforming uses may terminate within 40 or 20 years depending on inception/enactment timing (see code)	§ 10.07.040(C)
R‑1‑8 minimum lot area	8,000 sq ft minimum	§ 10.05.010; § 10.05.040
R‑1‑8 structural coverage / impervious	Structural coverage 30%, impervious 40% (with formula reductions by lot size/slope)	§ 10.05.040 (coverage rules)
ADUs and nonconforming conditions	ADUs allowed with development standards; state ADU law interacts with local nonconforming rules — Monte Sereno ADU rules in local chapter	ADU chapter (local ADU provisions)

Practical guidance / synthesis (plain‑English interpretation)

You can continue an existing lawful use or structure that no longer meets current zoning, but you generally cannot enlarge it, add floor area or expand its footprint beyond what existed when it became nonconforming. § 10.07.010 and § 10.07.030.
Routine maintenance and repairs are allowed, but Monte Sereno caps the value of repairs in a 12‑month period (the code limits work to 25% of assessed building value) and forbids increasing the nonconforming portion's floor area. § 10.07.030.
If the nonconforming use or part of a building is left vacant or unused for 12 months, the right to continue it ends automatically; likewise, a nonconforming use ends immediately upon abandonment or when it is changed to a conforming use. § 10.07.040(B).
If a nonconforming structure is badly damaged, the Monte Sereno code uses a 75% of assessed value rebuild threshold to determine whether the nonconforming right survives — exceeding that threshold terminates the nonconforming right. § 10.07.040(D).
Some older nonconforming uses face automatic sunset dates by operation of the ordinance (e.g., 20 or 40‑year time limits depending on the type of structure and the date the use began or became nonconforming). Verify applicable dates with the Planning Department for any specific property. § 10.07.040(C).

Checklist — what an applicant must satisfy when dealing with nonconforming uses/structures

Confirm the nonconforming status was lawful at time it became nonconforming (establish historic lawful use). § 10.07.010
If proposing repairs, ensure 12‑month repair cost does not exceed 25% of assessed building value; do not increase floor area of the former nonconforming portion. § 10.07.030
If the structure was damaged, calculate cost to repair relative to assessed value to see whether rights terminate at 75% threshold. § 10.07.040(D)
If vacancy or non‑operation has exceeded 12 months, be prepared that the right to the nonconforming use may be terminated. § 10.07.040(B)(3–4)
Check applicable district development limits (coverage, impervious surface, parking) — nonconforming structure may not be enlarged to exceed district maximums. See your district: R‑1‑8 § 10.05.040, R‑1‑20 § 10.05.030, RM § 10.05.043.
Confirm whether design review or a site development permit is required for any change (design review rules and site development triggers are in Chapter 10.08). § 10.05.046; design review chapter referenced in residential rules.

Note: when you discuss parking requirements with the City, use the Monte Sereno parking rules referenced in your district standards and the City's parking page.

Risks & Ambiguities

Issue	Why it matters	What to verify
Long‑stop termination windows (40/20/10/20 yrs)	Some nonconforming uses may be set to expire by operation of the code timelines in § 10.07.040(C); you could lose rights even without vacancy or damage.	Verify property‑specific history and the inception/enactment dates the City will rely on; confirm the applicable provision in § 10.07.040(C).
Damage threshold accounting (75% of assessed value)	Whether a damaged structure can be rebuilt as nonconforming depends on the damage valuation test in § 10.07.040(D).	Obtain assessor/building valuation and get City confirmation on what counts toward the 75% test. Verify with the jurisdiction.
ADUs vs. nonconforming zoning conditions	State ADU law affects how local nonconforming conditions are applied to ADU approvals; local ADU chapter interacts with nonconforming rules.	Check local ADU rules in the ADU section and confirm whether the nonconforming condition would require correction; see local ADU provisions. § 10.06.150 and ADU chapter.
Which coverage standard applies (district differences)	Structural/impervious coverage percentages vary by district and by lot size/slope formulas — mis‑applying the wrong district rule can cause noncompliance.	Confirm the parcel’s zone mapping and which subsection of 10.05.x contains the coverage/impervious formula that applies to your lot. Verify with the jurisdiction.
Repairs that incrementally expand nonconforming area	Small additions across multiple permits could be considered impermissible enlargements.	Any change that increases floor area of the nonconforming portion is prohibited under § 10.07.030; get planner confirmation before work.

Plain‑English Summary

If your building or use in Monte Sereno lawfully predates current zoning, you may continue it, but you cannot enlarge it, you must limit repair spending to the code cap, and your rights can be lost if the use is abandoned, the structure sits vacant for 12 months, or the building is so damaged that repair exceeds the 75% threshold in the ordinance. § 10.07.010–.040.

Source References

Monte Sereno Municipal Code, Chapter 10.07 — Non‑Conforming Uses and Structures (see § 10.07.010 through § 10.07.080)
Monte Sereno Municipal Code, Zoning District Regulations (Chapter 10.05) — district list and the specific district subsections: § 10.05.010, § 10.05.020, § 10.05.030, § 10.05.040, § 10.05.043, § 10.05.047.
Monte Sereno ADU provisions and amnesty: ADU chapter (local ADU rules and § 10.06.150 accessory unit amnesty).

Related pages (internal links used in this page):

Monte Sereno zoning & planning overview — general guide (first reference to site overview).
Monte Sereno Zoning — for district maps and base zoning rules.
Monte Sereno Development Standards — where coverage, impervious, and size rules live.
Monte Sereno Parking — for off‑street parking rules referenced above.
Monte Sereno Design Review — design review/site development permit triggers that can apply to changes.
Monte Sereno Overlay Districts — overlays (Conservation, Scenic Corridors) that can impose extra constraints.
Monte Sereno ADUs — local accessory dwelling unit rules that interact with nonconforming zoning.
California Building Standards Code — referenced where building and reconstruction interplay with planning (informational link; building code specifics are outside this page's scope).

Sources

Retrieved passages

Monte Sereno Zoning Code (Chapter shall) High relevance
Monte Sereno Zoning Code (Chapter or) High relevance
Monte Sereno Zoning Code (Chapter 10.07) High relevance
Monte Sereno Zoning Code (§ 1) High relevance
Monte Sereno Zoning Code (Section 10.01.020) Medium relevance
Monte Sereno Zoning Code Medium relevance
Monte Sereno Zoning Code (§1) Medium relevance
Monte Sereno Zoning Code (§ 66314) Medium relevance
Monte Sereno Zoning Code (§ 19300.5) Medium relevance
Monte Sereno Zoning Code (section is) Medium relevance
Monte Sereno Zoning Code (Chapter 3.01) Medium relevance
Monte Sereno Zoning Code (§ 4) Medium relevance
Monte Sereno Zoning Code (Chapter including) Medium relevance
Monte Sereno Zoning Code (§ 2) Medium relevance
Monte Sereno Zoning Code (Section the) Medium relevance
Monte Sereno Zoning Code (§ 2) Medium relevance
Monte Sereno Zoning Code (Section the) Medium relevance
CBC § 10.05.050 (Section 10.05.050) Medium relevance

Cited sections

Official Monte Sereno code library

Frequently asked questions

What is a nonconforming use in Monte Sereno?

A nonconforming use is a building or use that lawfully existed before the current zoning rules but does not meet those rules now; Monte Sereno defines this in the code and allows continuation subject to Chapter 10.07 limitations (no enlargement, maintenance limits, and termination rules). § 10.07.010

Can I expand a nonconforming structure in Monte Sereno?

No. The ordinance forbids increasing the size or floor area of a nonconforming structure beyond what existed when it became nonconforming; conversion to a conforming structure is allowed but cannot be re‑established as nonconforming. § 10.07.010; § 10.07.060(A)

What maintenance or repair am I allowed for a nonconforming building?

Ordinary maintenance and repairs are permitted, but the cost of such work in any 12‑month period may not exceed 25% of the building's assessed value, and the nonconforming floor area cannot be increased. § 10.07.030

If my nonconforming business stops operating, when do I lose the right to operate it again?

Monte Sereno terminates the right to a nonconforming use if the use or part of the structure is not operated for 12 consecutive months; abandonment or change to a conforming use also terminates the right immediately. § 10.07.040(B)

What happens if a nonconforming building is damaged by a storm or fire?

If repairing the damage would cost more than 75% of the structure’s assessed value, the right to maintain the nonconforming use/structure terminates; limited reconstruction is allowed if started timely and does not increase pre‑damage nonconforming features. § 10.07.040(D); § 10.07.070–.080

Do ADUs (Accessory Dwelling Units) change the nonconforming rules?

Monte Sereno allows ADUs under its ADU chapter; state ADU law also restricts when a local agency may require correction of nonconforming zoning conditions. The local ADU provisions and amnesty rules should be consulted together with Chapter 10.07 for specifics. See the local ADU rules (local ADU chapter) and § 10.06.150 for amnesty terms.

How do district development standards (coverage, impervious, parking) affect nonconforming lots?

Nonconforming structures may continue, but you cannot expand them to violate district development standards (structural coverage, impervious area, parking). Check your parcel’s zoning (R‑1‑8, R‑1‑20, RM etc.) for the exact coverage and parking numbers in the district subsection. § 10.05.030–.040 (coverage/parking rules)

If I repair a nonconforming structure, do I need design review or a site development permit?

Some changes (new main houses, second stories, large additions) trigger site development or design review per Chapter 10.08 and the district rules; always confirm whether your proposed work triggers design review before proceeding. § 10.05.046; site development permit triggers in § 10.08.040.

Are there time limits after which a nonconforming use automatically ends?

Yes — the code includes operation‑of‑law termination timelines (for example, main building nonconforming uses and other permanent structures may have 20 or 40‑year limits depending on inception and enactment dates); consult § 10.07.040(C) for the precise rule applied to your case. § 10.07.040(C)

Who should I contact to verify whether my property is nonconforming and what applies?

Contact the City Planning Department for a determination; verify your parcel zoning, the date the nonconforming condition arose, assessor values used for repair thresholds, and whether any PD or overlay modifies base district rules. Chapter 10.07 lays out the legal tests; the Planning Department applies them to parcels. § 10.07.010–.080 ---

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