San Gabriel Zoning and ADU Guide for Homeowners

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

San Gabriel regulates accessory dwelling units under Municipal Code Section 153.047, which caps detached ADUs at 850 square feet for a studio or one bedroom and 1,000 square feet for two bedrooms. This guide summarizes the city’s ADU section of the zoning code as published by American Legal Publishing, including sizes, height, setbacks, parking, owner occupancy and review time.

The city has amended its ADU rules more than once, so confirm the current text with the Planning Division before you design or buy.

San Gabriel ADUs at a glance

Detached ADU size	850 sq ft for a studio or one-bedroom; 1,000 sq ft for two bedrooms
Attached ADU size	No more than 50% of the main dwelling, or the detached limit, whichever is less
Junior ADU	Up to 500 sq ft; owner occupancy required unless the owner is a government agency, land trust or housing organization
Height	16 feet; 18 feet near major transit or on multifamily lots; 25 feet, not over two stories, if attached
Setbacks	4 feet from side and rear lot lines; front setback applies to detached units unless it blocks an 800 sq ft ADU
Parking	1 space per bedroom or unit, whichever is less, with exceptions
Rentals	Rented for terms longer than 30 days
Review time	Complete-application notice within 15 business days; approval or denial within 60 days

Size limits

Section 153.047(D) allows a maximum of 850 square feet for a studio or one-bedroom detached ADU and 1,000 square feet for a two-bedroom detached ADU. When an ADU is attached to the primary home, section 153.047(E) limits it to 50% of the main dwelling size or the detached limits, whichever is less.

A junior ADU is limited to 500 square feet. If you own an older unit, measure it against these numbers, because an oversized unit is one of the reasons legalization can be hard.

Height and setbacks

The code sets a height limit of 16 feet from the lowest adjoining grade to the highest point.

Exceptions allow 18 feet, plus two feet for roof pitch, on a lot within a half mile walking distance of a major transit stop or high-quality transit corridor, 18 feet on a lot with an existing or proposed multifamily, multi-story dwelling, and up to 25 feet, not over two stories, for an attached ADU.

Units must be set back at least four feet from side and rear lot lines. Detached units must meet the front setback for the zone unless the applicant shows it prevents an 800 square foot ADU, and no setback is required when a legally permitted garage or accessory structure is converted.

Parking

The code requires one space per bedroom or unit, whichever is less, and it can be covered, uncovered, a mechanical lift or a tandem space on the driveway.

Parking is not required when the ADU is within a half mile walking distance of public transit, inside an architecturally and historically significant historic district, where on-street permits are required but not offered to the ADU occupant, within a block of a car share vehicle, or when the ADU is permitted with a new home.

Converting a garage or carport does not require replacement parking, and a junior ADU cannot be required to add parking.

Historic districts and rentals

Section 153.047(O)(2) allows ADUs in designated historical districts, but they must not be visible from the public right-of-way. ADUs must be rented for terms longer than 30 days, and a junior ADU may not be rented for less than 30 days. Owner occupancy applies to junior ADUs in the single-family residence, and the owner may live in either the main home or the junior unit.

Review time, fees and utilities

The city must tell you whether your application is complete within 15 business days and must approve or deny a complete application within 60 days when there is an existing home on the lot.

The code says impact fees are not charged for an ADU under 750 square feet, and larger units are charged in proportion to the main home. An ADU may be separately metered, and a junior ADU is not treated as a new dwelling for water, sewer or power connection purposes.

Legalizing an older unit before a sale

If you own a garage conversion or backyard unit with no permit, you have two paths. You can apply to legalize it, which means plans, plan check, inspections and corrections to meet current life-safety rules. Or you can disclose the unit and sell as-is. The city pages we read do not describe a separate amnesty program, so ask Planning and Building and Safety what applies to your property.

State ADU law and San Gabriel

California’s ADU statute, Government Code section 66314 and following, sets a floor that every city must follow, and local ordinances fill in the details.

The state requires ministerial review within 60 days of a complete application, bars a city from requiring more than a limited set of standards, and generally allows an ADU or conversion inside existing space without added setbacks.

The California Department of Housing and Community Development (HCD) publishes a handbook and keeps a list of the state requirements. Because state law changes often, treat the city’s current ordinance and handout as the final word on size, height, parking and fees for your lot.

ADUs, garage conversions and selling a San Gabriel house

Many older homes have a converted garage or a backyard unit built without permits. Buyers and lenders ask about them, and California sellers generally disclose known unpermitted work. Our guide to selling as-is with unpermitted work explains the rules, and our Prop 13 guide explains how new construction can affect property tax. Before you list:

• Check city records for permits on any ADU, conversion or addition.
• Ask Planning whether the structure could qualify under current rules.
• Estimate plans, fees and corrections needed to legalize it.
• Compare that with selling as-is and letting a cash buyer take on the legalization.

Questions to ask Planning before you design

• Does my lot and zone allow an ADU, a junior ADU, or both?
• Is a pre-approved or pre-reviewed ADU plan available?
• What are the current impact, utility and school fees for the size I am considering?
• Can my existing garage or accessory structure be converted without changing its footprint?
• Are there fire, slope, easement or utility constraints on my lot?

Junior ADUs and garage conversions in more detail

State law treats a junior ADU as a unit of up to 500 square feet created inside the walls of an existing or proposed single-family home, with an efficiency kitchen and a recorded restriction that keeps it from being sold apart from the house.

A garage conversion is a different path: the unit replaces the garage, and state law generally does not require the city to demand replacement parking. Both are common sources of unpermitted space in older San Gabriel neighborhoods, which is why buyers’ agents and appraisers ask for the permit record.

If a conversion was done without a permit, the usual fix is to submit as-built drawings, pay the fees and pass inspection, which can take months and cost real money.

Fees, utilities and property tax

State law limits the impact fees a city can charge on smaller ADUs and on conversions of existing space, and it limits when a separate utility connection can be required.

Larger new units can still carry impact fees, school fees and water or sewer connection charges, so ask for an itemized estimate before you commit to plans. New construction is generally reassessed for property tax under Prop 13, which means an ADU can raise the bill for the whole property. Our Prop 13 guide explains how reassessment works.

Why ADUs matter for resale

A permitted ADU can add rental income and appeal for some buyers, but an unpermitted one can complicate financing and appraisal. Lenders typically want permitted living area, and an appraiser may not count unpermitted space.

Because an ADU generally cannot be sold separately from the main home, its value comes through the sale of the whole property.

If you inherited a house with an old backyard unit, or bought one with a converted garage, check what the city has on file before you decide how to sell. Our probate home sale guide covers inherited property.

How to sell a house in San Gabriel

1. Pull the permit record for your address from the Building and Safety Division.
2. Gather permits, final inspection sign-offs and any city notices.
3. Request a no-obligation cash offer for the house as it stands.
4. Choose your closing date.
5. Close with no repairs, permit cleanup or showings required.

See also our San Gabriel page, the sell as-is page, the sell fast page, the cash offer process, the inherited house page and the Los Angeles County hub.

Frequently asked questions

How big can an ADU be in San Gabriel?

Section 153.047 allows up to 850 square feet for a studio or one-bedroom detached ADU and up to 1,000 square feet for two bedrooms, with attached ADUs limited to 50% of the main dwelling.

Are junior ADUs allowed?

Yes, up to 500 square feet within a single-family home, with owner occupancy required unless the owner is a government agency, land trust or housing organization.

How long does the city take to review an ADU?

The code requires a completeness notice within 15 business days and approval or denial within 60 days of a complete application.

Do I need parking for an ADU?

One space per bedroom or unit, whichever is less, with exceptions such as transit within a half mile or a historic district.

Can I rent my ADU short term?

No. The code says ADUs must be rented for terms longer than 30 days.

Can I sell a house with an unpermitted ADU?

Yes. You can disclose it and sell as-is, including to a cash buyer.

More guides

• We Buy Houses in San Gabriel
• We Buy Houses in Los Angeles County
• Los Angeles County Property Tax Guide
• San Gabriel Building Permits Guide
• San Gabriel Code Enforcement Guide
• Alhambra Building Permits Guide
• Monterey Park Building Permits Guide
• All California Guides

Sources

• San Gabriel Municipal Code Section 153.047: Accessory Dwelling Units and Junior ADUs
• City of San Gabriel: Accessory Dwelling Units (ADU) Ordinance
• City of San Gabriel: Building and Safety Division

This guide is general information from public sources, not legal advice. Confirm current rules, fees and hours with the city.