Los Angeles County

Alhambra ADU rules

Research summary of local ADU rules on file for Alhambra in Los Angeles County. Not a determination for a specific lot.

Last checked October 23, 2026.

City or county ADU page

Alhambra rules on file

Local rules recorded in this project for this jurisdiction. Where a city figure on file is stricter than the state baseline on file, both are shown.

How many units
Single-unit lot: one detached or attached ADU, one conversion ADU and one junior ADU. Multi-unit lot: two detached ADUs with a proposed building or up to eight with existing buildings (not more than existing units), plus conversions of non-livable space up to 25% of units; no junior ADUs.
Source: City of Alhambra, ADU Informational Handout (November 2025), What Type of ADU Can I Build?, accessed 2026-10-23.

ADU size
State-exempt detached ADU: up to 800 sq ft. Under City standards on single-unit lots: detached up to 1,200 sq ft; attached up to 50% of the main home or 850 sq ft (one bedroom or less) or 1,000 sq ft (two or more bedrooms), whichever is greater. Multi-unit lots: 850 or 1,000 sq ft. Conversions within existing structures: no size limit.
Source: City of Alhambra, ADU Informational Handout (November 2025), ADU Size, accessed 2026-10-23.

Floor area and lot coverage
ADUs over 800 sq ft must meet the zone's floor area ratio and lot coverage limits; ADUs of 800 sq ft or less with 4-foot setbacks are exempt from these standards.
Source: City of Alhambra, ADU Informational Handout (November 2025), Floor Area Ratio; Lot Coverage, accessed 2026-10-23.

Setbacks and separation
4-foot side and rear setbacks for new construction; none for conversions within existing structures (with fire and safety clearance). Exterior mechanical equipment at least 3 feet from property lines. 5 feet eave to eave between buildings. ADUs under City standards may cover no more than 40% of the required rear yard.
Source: City of Alhambra, ADU Informational Handout (November 2025), Setbacks; Building Separation; Rear Yard Coverage, accessed 2026-10-23.

Height
Two stories and 25 feet.
Source: City of Alhambra, ADU Informational Handout (November 2025), Height, accessed 2026-10-23.

Design
ADUs under City standards must use the main home's exterior materials, colors, roof covering and architectural details (recommended, not required, for state-exempt ADUs).
Source: City of Alhambra, ADU Informational Handout (November 2025), Design, accessed 2026-10-23.

Access and living space
Every ADU needs exterior access separate from the main home and a living/sleeping area, a kitchen or kitchenette (stove or hotplate, refrigerator and sink) and a bathroom with a shower or tub.
Source: City of Alhambra, Accessory Dwelling Units (ADUs) page (Planning Division), Requirements for All ADUs, accessed 2026-10-23.

Parking
One space per ADU, none within a half mile of public transit (bus stops included), for conversions of existing space, or on designated historic properties. Garage or carport spaces removed for an ADU do not have to be replaced. No parking for junior ADUs.
Source: City of Alhambra, Accessory Dwelling Units (ADUs) page (Planning Division), Lots with Single-Family Structures: Parking, accessed 2026-10-23.

Junior ADU
Up to 500 sq ft within a single-family home, with a living/sleeping area and a kitchen or kitchenette; no bathroom needed if it has direct access to the main home. Any expansion is limited to 150 sq ft for ingress and egress.
Source: City of Alhambra, Accessory Dwelling Units (ADUs) page (Planning Division), Lots with Single-Family Structures: JADU Development Standards, accessed 2026-10-23.

Review time
ADU and junior ADU building permits are reviewed ministerially within 60 days of a complete application.
Source: Alhambra Municipal Code Section 23.22.040, Accessory Dwelling Units, 23.22.040, accessed 2026-10-23.

How to apply
Submit an “ADU Permit” through the online Permit Portal (each detached ADU needs its own permit), then upload Planning-cleared plans to the GoPost plan check portal. Building reviews for Building, Fire and Public Works; Utilities reviews separately. Outside sign-offs: LA County Sanitation, the school district (ADUs over 500 sq ft) and AQMD if there is demolition. Every ADU needs an address assignment. First review takes about 2 to 4 weeks.
Source: City of Alhambra, ADU Guide and Frequently Asked Questions (Building Division), Steps to Plan Checks and Permit Issuance, accessed 2026-10-23.

Typical permit fees
City examples total about $11,677–$14,012 in building permit, plan check and related fees for an 850 to 1,200 sq ft ADU, not counting mechanical, electrical and plumbing permits.
Source: City of Alhambra, ADU Informational Handout (November 2025), Estimated Permitting Costs, accessed 2026-10-23.

Utilities
A separate utility meter or service panel is not required (it may be requested). The ADU may connect to the existing house sewer or have its own line.
Source: City of Alhambra, ADU Guide and Frequently Asked Questions (Building Division), Questions 6 and 7, accessed 2026-10-23.

Who to contact
Planning Division, (626) 570-5034, planning@alhambraca.gov.
Source: City of Alhambra, ADU Informational Handout (November 2025), ADU Informational Handout, accessed 2026-10-23.

California state rules on file

The statewide baseline recorded from state law and the HCD ADU Handbook.

Detached size cap described in state law
1,200 sq ft. Recorded in this rules file from Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Side and rear setback cap for a new ADU
4 ft. Recorded in this rules file from Government Code section 66314, which describes a cap on side and rear setbacks for a new ADU.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Setback for a conversion of an existing structure
No additional setback, as recorded in this rules file from Government Code section 66314 for a conversion of an existing structure.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Minimum lot size
A city may not impose a minimum lot size for an ADU, as recorded in this rules file from Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Minimum unit the handbook says cities must allow
At least an 800 sq ft ADU with 4 ft side and rear setbacks. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(3).
Source: HCD ADU Handbook, 66321(b)(3); handbook updated March 2026, accessed 2026-10-16.

Detached height described in the handbook
16 ft, or 18 ft or 20 ft in some cases. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(4).
Source: HCD ADU Handbook, 66321(b)(4); handbook updated March 2026, accessed 2026-10-16.

Permit decision deadline
60 days. Recorded in this rules file from Government Code section 66317(a)(3): the permitting agency must decide on (approve or deny) a completed ADU application within 60 days when an existing single-family or multifamily dwelling is on the lot. Section 66317(a)(1) says the application is considered ministerially, without discretionary review or a hearing.
Source: California Government Code section 66317, 66317(a)(1), (a)(3), accessed 2026-10-17.

Owner-occupancy requirement
None. Recorded in this rules file from Government Code section 66315: a local agency may not impose an owner-occupancy requirement on an ADU. It may require that the property be used for rentals of terms 30 days or longer. The HCD ADU Handbook (updated March 2026) describes the same rule.
Source: California Government Code section 66315, 66315; HCD ADU Handbook updated March 2026, accessed 2026-10-17.

Parking near public transit
No parking standards within one-half mile walking distance of public transit. Recorded in this rules file from Government Code section 66322(a)(1). Section 66322(a) lists several other cases where parking standards may not be imposed.
Source: California Government Code section 66322, 66322(a), accessed 2026-10-17.

Ministerial categories
The HCD ADU Handbook (updated March 2026) states that Government Code section 66323 sets four ministerial categories. This rules file does not restate those four categories.
Source: HCD ADU Handbook, 66323; handbook updated March 2026, accessed 2026-10-16.

Fire Hazard Severity Zones
If your lot is in a Fire Hazard Severity Zone, the CAL FIRE Office of the State Fire Marshal says in Information Bulletin 25-004 (issued March 3, 2025): “Fire Hazard Severity Zones (FHSZs) should not restrict the development of Accessory Dwelling Units (ADUs). However, additional building standards may be necessary, including but not limited to California Fire Code Chapter 49 and California Building Code Chapter 7A.” State ADU law does not itself bar an ADU there. A city or county may still apply its building code, including wildfire-resistant construction (Gov. Code 66314(d)(8)); require side and rear setbacks “sufficient for fire and safety” for a unit converted under 66323(a)(1); and decline parking in setbacks on specific fire and life safety findings (66314(d)(10)(B)). It may also consider public safety when it designates where ADUs may be permitted (66314(a)). Sprinklers can't be required in an ADU or JADU if the primary residence doesn't need them (66314(d)(12), 66323(d)). Some cities and counties still apply their own fire-zone limits. Where this summary has one, it is listed with the local rules. This summary does not look up your lot. Check the CAL FIRE Fire Hazard Severity Zone map viewer linked from the State Fire Marshal's Fire Hazard Severity Zones page: https://experience.arcgis.com/experience/5065c998b4b0462f9ec3c6c226c610a9
Source: CAL FIRE Office of the State Fire Marshal Information Bulletin 25-004, page 4, issued March 3, 2025; Gov. Code 66314, 66323, accessed 2026-10-20.

State baseline on the directory → · State ADU rules on the homepage →

Can I build an ADU in Alhambra?

State law sets a baseline for ADUs in Alhambra, and the local standards on file are listed on this page. Whether a specific lot can add an ADU depends on zoning, utilities, and other site facts this page does not measure. Confirm with the City of Alhambra Community Development Department (Planning Division), or run a free address summary.

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