Accessory Dwelling Unit

Building Division Counter Hours: 8:00 am to 5:00 pm, Plan Check counter hours: 8:00 am to 12:00 pm (Effective October 31, 2019, our new business hours will be 7:00 am to 5:30 pm, Monday - Thursday, Closed on Fridays. New Plan Checker counter hours will be 7:00 am to 12:00 pm, Monday - Thursday)

What is an ADU?

In 2016, the State Legislature approved two amendments to State Law which required local agencies to ministerially consider accessory dwelling unit (or ADU) applications in residential zones. The legislation consists of Assembly Bill 2299 and Senate Bill 1069, which together amended California Government Code Section 65852.2. This legislation is the result of a statewide housing crisis, rising housing costs, and a shortage of affordable housing options.

On December 11, 2017, the City Council adopted Ordinance No. O2M17-4724 amending Title 23 (Zoning) of the Alhambra Municipal Code, Chapter 23.57 regarding permitting of accessory dwelling units in all residential zones to comply with state’s requirements.

An ADU is an attached or detached residential dwelling unit which provides complete independent living facilities for one or more persons, and includes permanent provisions for living, sleeping, eating, cooking (i.e., stove, refrigerator, and sink), and sanitation (i.e., bathroom, with shower or bathtub) on the same parcel where an existing single-family dwelling is situated.


What kind of ADUs are there?

There are three (3) kinds of ADUs, a conversion of an existing accessory structure or portion of a dwelling unit, a detached ADU, and an attached ADU. ADUs can be attached or detached (free standing) to an existing single family home. New ADUs have to adhere to all development and design standards of that zoning designation. When a portion of the existing home or an existing accessory structure is converted into an ADU, it is exempt from meeting certain development and design standards.


ADU Development Standards

ADUs are permitted on all residentially zoned properties (R-1, R-2, & R-3). However, an ADU can only be placed on residential lots containing not more than one (1) single-family residence.

All new ADUs shall be constructed on properties that are not smaller than 50’ 0” X 130’ 0” (6,500 SF) and shall not exceed the floor area ratio (FAR) associated with the property’s zoning designation. Independent access to the ADU, separate from the main residence entrance, is required. All ADUs shall have a living/sleeping area, a full operational kitchen (i.e., stove, refrigerator, and sink), and a bathroom includes a shower or bathtub.


ADUs shall adhere to all applicable zoning designation’s setbacks outlined in the Alhambra Municipal Code Section 23.42.020 [Property Development Standards] (click here). Existing accessory structures and single family homes that are converted into ADUs are exempt from meeting the required setbacks as pursuant to Government Code Section 65852.2.



All new ADUs will be required to provide one (1) additional parking space, cover or uncovered. However, accessory structures or a portion of the existing residence is converted into an ADU no additional parking is required if the property is within 1/2 mile of a public transit system. If a garage is converted into an ADU the parking spaces within the garage shall be replaced with the required number of parking spaces pursuant to AMC Section 23.52.040 [Number of Parking Spaces Required] which can be covered or uncovered.



The property owner shall occupy either the existing single-family residence or the ADU in order to be eligible to have an ADU on the property. The property owner will be subject to sign Deed Restriction, filed and recorded by the County, affirming the property owner will live on the property as part of the approval process. The unit not occupied by the property owner shall not be rented for a period less than 30 days and shall not be sold separately from the main dwelling unit.


Application Process

An ADU requires Design Review Board (DRB) approval. Upon approval from DRB, applicants will proceed by submitting for Plan Check with the Building Division. The Building Division will then route plans to each of the applicable Divisions for review.  Upon receiving departmental approvals, the applicant will then be issued a Building Permit.



Prior to submitting an application to the Planning Division, a review shall be conducted by staff to ensure that your proposed project will meet all ADU Standards with the City of Alhambra and the State of California. If you have any questions or concerns regarding the ADU Development Standards or the ADU application process, please contact the Planning Division at (626) 570-5034 or

Accessory Dwelling Unit Guidelines

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