San Gabriel Valley · LA County
ADU permits in San Marino
Zip codes:91108
San Marino is a small independent city of about 13,000 people in the San Gabriel Valley (SGV), bordered by Pasadena to the north and South Pasadena to the west. It runs its own building and planning departments. San Marino is overwhelmingly single-family residential with large lots, top-rated schools, and one of the most exclusive housing markets in Los Angeles County.
Independent city — not LADBS
San Marino runs its own building department. Permits go through San Marino Planning + Building Department ↗, not the Los Angeles Department of Building and Safety (LADBS). Our address checker pulls real zoning + overlay data for any Los Angeles County address. The San Marino ordinance breakdown below covers the city-specific permit path.
San Marino by the numbers
Rounded figures from the 2020 US Census, LA County Assessor parcel data, and the city's own published reports. Estimates only — your specific lot can vary widely.
Population
13,000
2020 Census
Single-family homes
~4,500
LA County Assessor
Median lot size
12,000 sqft
Approximate
Median home value
$3.3M
Zillow / Redfin
What makes San Marino different
San Marino's ADU ordinance is in San Marino Municipal Code Title 23. The city was one of the most restrictive ADU jurisdictions in California pre-2020; state preemption forced state-baseline alignment but the city retains heavy design review. Plan check + design review combined typically runs 75-120 days.
San Marino ADU ordinance — the rules that apply
Last verified: 2026-05-12
The current ADU rules in San Marino, sourced from the city's published ordinance and verified against CA Government Code §65852.2 (which preempts local rules stricter than state baselines). When you see "state default," that means the city can't reduce below this number under state law.
| Max detached ADU size | 1,200 sqft (state default) |
| Max ADU height | 16 ft / 18 ft with second-story setbacks |
| Setbacks | 4 ft side / 4 ft rear (state minimum) |
| Design review | Required for all ADUs Citywide. Architectural compatibility with the existing primary residence is the standard. |
| Historic-preservation overlay (most of the city) | Stricter design review for pre-1950 homes Covers a meaningful share of the city's housing stock. |
| Local processing time | 75-120 days with design review |
| Pre-approved standard plans | None city-specific |
Active overlays + extra rules in San Marino
City overlays + state-level designations that hit a meaningful share of San Marino parcels. Each affects what you can build, how long it takes, or how much it costs.
Historic-Preservation Overlay
~45% of parcelsPre-1950 homes face stricter exterior-compatibility design review.
Mature-canopy tree protection
~30% of parcelsSan Marino actively protects mature street + lot trees. ADU foundations within a protected tree's drip line require arborist sign-off.
Watch-outs specific to San Marino
Patterns we see across San MarinoADU permits. None are dealbreakers — they're just the things people get wrong most often.
- 01
Design review here is unusually rigorous
San Marino's design review goes beyond most LA-area cities. Architects experienced with the city's review board are worth the premium. Modern or contrasting-material ADU designs face long pushback cycles.
- 02
Tree-protection rules can constrain ADU placement
Mature trees on or adjacent to your lot have protected drip lines. If you want to build under a protected tree's canopy, you'll need an arborist's sign-off and possibly a tree-protection plan.
- 03
San Marino Unified school fees apply
San Marino Unified School District (SMUSD) charges school facility fees on ADUs over 500 sqft. SMUSD is one of California's highest-ranked public districts.
Need a person, not a wizard?
Routes that fit San Marino
Based on what we know about San Marino, these are the lead types that usually make sense here. Pick whichever fits your situation. All free, no obligation.
Complex permit context
Request a San Marino permit referral
Coastal, hillside, historic, fire-zone, or multi-overlay parcels in San Marino usually mean a permit expediter pays for itself in saved months. We work with vetted Los Angeles permit expediters and expeditors (both spellings) who've handled San Marino projects.
Complex permit context
Request a San Marino permit referral
Coastal, hillside, historic, fire-zone, or multi-overlay parcels in San Marino usually mean a permit expediter pays for itself in saved months. We work with vetted Los Angeles permit expediters and expeditors (both spellings) who've handled San Marino projects.
Talk to our financing broker
Want someone to walk you through your options?
Our in-house broker has 30+ years in LA mortgage and ADU financing. He'll lay out HELOC, construction-to-perm, and ADU-specific products like Renofi against your situation — free, no obligation.
Talk to our financing broker
Want someone to walk you through your options?
Our in-house broker has 30+ years in LA mortgage and ADU financing. He'll lay out HELOC, construction-to-perm, and ADU-specific products like Renofi against your situation — free, no obligation.
Plans that fit San Marino lots
San Marinodoesn't maintain a city-specific pre-approved plan library the way the Los Angeles Department of Building and Safety (LADBS) does. California Department of Housing and Community Development (HCD)-approved prefab (which bypasses local plan check) and custom designer plans are the main paths:
Amenities + civic services in San Marino
Parks, libraries, and the school district that serve the area. Context that matters for renter appeal, family relocation, and long-term resale.
Parks + sports
Lacy Park
Virginia Road, central San Marino
30-acre park — San Marino's only public park. Tennis, walking paths, mature trees. Paid weekend admission for non-residents.
Paid weekend admission for non-residents (residents free)
- Tennis
- Playground
- Trails
- Picnic
Stoneman Park
South Pasadena Avenue + Stoneman Lane
Small neighborhood park on the south side of the city.
- Playground
- Picnic
Libraries
Crowell Public Library
Other
West Huntington Drive, civic center
Independent San Marino Public Library system (technically Crowell Public Library), not part of LA County Library.
Public schools
School assignments vary by exact address. The district + notable schools below cover most of the area.
District
San Marino Unified School District (SMUSD)
Notable schools in the area
- San Marino High School
- Huntington Middle School
- Carver Elementary
SMUSD is consistently one of the highest-ranked public school districts in California. Primary driver of San Marino home premiums (home values track the district's enrollment boundaries).
Getting around San Marino
Car-dependent throughout. No rail or significant bus service.
Transit + walkability
Bus lines
- Pasadena Transit (limited)
- Metro 79 (San Marino-adjacent)
Nearest rail
Metro A Line — Memorial Park Station (in Pasadena, about 2 miles north)
Walkability
Mostly car-dependent. Mission Street commercial strip is the only walkable pocket.
Nearby airports
Distance + type for each major Los Angeles-area airport reachable from San Marino. Useful for travel, commute, and any flight-path noise concerns on specific parcels.
Hollywood Burbank Airport (BUR)
~12 miRegional / domestic
Los Angeles International (LAX)
~22 miInternational
Community + landmarks in San Marino
Annual events, landmarks, and the places that anchor the area's identity. Context for renter appeal and long-term resale.
Annual events
What makes San Marino San Marino
Museum + gardens
The Huntington Library, Art Museum, and Botanical Gardens
One of the most-visited cultural institutions in Los Angeles. 120 acres of gardens + Gutenberg Bible + Blue Boy. Internationally renowned.
Public park
Lacy Park
30-acre park that doubles as the city's signature gathering space.
Nearby areas to San Marino
Other Los Angeles-area pages worth a look. Each one runs different Accessory Dwelling Unit (ADU) rules depending on jurisdiction — we show you what changes when you cross a city or county line.
Independent city
Pasadena →
Large bungalow-belt lots support strong Accessory Dwelling Unit (ADU) economics, but Pasadena's Landmark Districts cover a meaningful share of the city and add design-review time to any exterior-visible ADU.
Independent city
South Pasadena →
Strong walkability, the Metro A Line (Gold Line), Mission Street historic district, and Pasadena Unified-adjacent home values give South Pasadena unusually strong Accessory Dwelling Unit (ADU) economics for a small SGV city.
LA County unincorporated
Altadena →
Altadena's large historic lots and Los Angeles County jurisdiction (LADBS rules don't apply here) make Accessory Dwelling Unit (ADU) economics attractive, but the active rebuild context, Very High Fire Hazard Severity Zone (VHFHSZ) rules, and county-not-city permitting all add complexity worth understanding upfront.
Frequently asked questions about San Marino ADUs
›Can I build an ADU in San Marino?
Yes. San Marino allows ADUs under its local ordinance, aligned with California Government Code §65852.2 (the state baseline that preempts overly-strict local rules). Most single-family lots can host one ADU plus one JADU. Permits go through San Marino Planning + Building Department, not LADBS — see the ordinance table above for the specific rules.
›How does San Marino differ from LA City for ADU permits?
Three main differences: the permit agency (San Marino Planning + Building Department vs. LADBS), the local ordinance details (each city has some flexibility above the state baseline), and the timeline (some cities are faster, some slower than LA's 60-day plan check). See the ordinance breakdown above for the specifics on each.
›How much does it cost to build an ADU in San Marino?
Median home value in San Marino is around $3.3M, which usually means lot economics support a quality ADU build of $200K–$400K all-in. Hillside, coastal, or VHFHSZ lots add 7–25% on top. HCD-prefab units (Connect Homes, Cover, Plant Prefab) bypass local plan check entirely and typically run $190K–$350K turnkey.
›Does San Marino have pre-approved standard plans like LA's YOU-ADU?
No. Unlike LADBS, San Marino does not maintain a city-specific pre-approved plan library. The two faster paths are an HCD-approved prefab (factory-certified, skips local plan check) or a custom designer drawing for your lot. The slower path is a fully custom architect-led design.
›Will the PermitPathLA wizard work for my San Marino address?
Yes. The wizard pulls real zoning, overlay, and parcel data for any Los Angeles County address, including San Marino. What you'll see today: feasibility for your specific lot, the overlays that apply, and a routing summary pointing at San Marino Planning + Building Department for the permit submittal. Deeper San Marino-specific permit walkthroughs are next on the roadmap as we expand from LADBS into the independent-city ordinances.
Ready to see what your San Marino lot can do?
Our free address checker pulls real zoning, overlay, and parcel data for any Los Angeles County address — including San Marino. Start there and we'll surface what applies to your specific lot.
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