City of Altadena ADU
Regulations
Everything you need to know about building Accessory Dwelling Units (ADUs) in Altadena, CA.
Overview
A recent ordinance in Altadena City, California, allows for the construction of ADUs in all single-family homes. This will allow homeowners within the city limits to build secondary units on their properties without having to go through a lengthy and costly approval process.
Building an ADU is a great way to add extra living space to your home, but the process can be complex and confusing. At Vision ADU, we specialize in helping homeowners in Altadena build beautiful and functional ADUs. We'll work with you to figure out the best design for your needs and budget, pull all the required permits, and manage the construction process from start to finish.
Type of ADUs
The following type of Accessory Dwelling Units (ADUs) are allowed in Altadena, California.
 Attached ADU
An Attacched ADU connects to an existing house, typically through the construction of an addition along the home’s side or rear.
Max 1,000 sq. ft.
Detached ADU
An Attacched ADU connects to an existing house, typically through the construction of an addition along the home’s side or rear.
Max 1,200 sq. ft.
Garage Conversion
An Attacched ADU connects to an existing house, typically through the construction of an addition along the home’s side or rear.
Max 1,200 sq. ft.
Junior ADU
An Attacched ADU connects to an existing house, typically through the construction of an addition along the home’s side or rear.
Max 500 sq. ft.
Altadena Property Requirements
Several rules and regulations must be followed when building an ADU in Altadena. These include:
Number of ADUs Allowed
Single-family lots can build 1 attached ADU or 1 detached ADU with 1 JADU.
Multi-family lots are allowed a maxium of 2 detached ADUs.
ADU Size
850 square feet of floor area for a studio/1 bedroom.
1,000 square feet for 2 bedrooms (no more than two bedrooms are allowed)
Height Limit
The maximum height is 16 feet, measured to the top of the roof ridge, and the unit shall not exceed one story.
Number of Bedrooms Allowed
Altadena allows 2 bedrooms.
Setbacks
4 feet from the property line is the minimum side and rear setbacks required for an attached or detached ADU. There are no minimum setbacks requirements for garage conversions or JADUs unless it is needed to ensure fire safety.
Parking
1 uncovered or covered parking structure is required unless the property has physical limitations. An alternative parking arrangement may be made subject to a parking waiver in such a case.
Owner Occupancy
JADUs are subject to an owner-occupancy requirement, the property owner must live on the property. All other ADUs built in Altadena after January 1, 2020, but before January 1, 2025, are not subject to any owner-occupancy requirement.
Rental Guidelines
You can rent out your ADU on a long-term basis. Short-term rentals such as Airbnb or anything less than 30 days may not be allowed in your neighborhood.
Altadena is a small city located in Los Angeles County, California. The city is situated at the base of the San Gabriel Mountains and has a population of just over 44,000. Altadena is known for its beautiful homes and gardens, as well as its proximity to hiking trails and outdoor recreation. One of the most popular attractions is the Mount Lowe Railway trail.
