ADU regulations have drastically changed for the better in 2025. If this news doesn’t inspire you to start your ADU project, I don’t know what will because it is now easier than every to add a brand new housing unit to your property.
Even better, the California Department of Housing and Community Development (HCD) has finally released a new and improved ADU Handbook, already updated with the new bills that were just passed in California.
But, before you start combing through this hefty 54 page document, I’ve already taken the main key points and prepared this easy-to-digest summary to get you started. Let’s get into it.
What is the HCD ADU Handbook?
The HCD ADU Handbook is a comprehensive guide created by the California Department of Housing and Community Development (HCD) to help homeowners, designers, and contractors navigate the state’s Accessory Dwelling Unit (ADU) regulations. Serving as an authoritative resource, the handbook breaks down state laws governing ADU construction, providing clarity on zoning, permits, size requirements, and more. It also outlines how state regulations interact with local ordinances, helping ensure compliance across jurisdictions.
Prior to this update, the Handbook, while incredibly helpful, had not been updated since 2022. If you’ve kept up with ADUs over the last few years or even months, you’ll know that ADU regulations change quickly and often. As such, the Handbook was long overdue for an update.
California ADU Regulations in 2025
California has established a set of state ADU regulations that all cities within the state are obligated to adopt. Cities can establish their own ordinances, but they cannot enforce regulations stricter than those set by the state. For instance, some cities have increased the maximum allowable size for ADUs, but they cannot reduce it below the state-defined limit.
To give you a good foundation before I get into the finer details, below are the basic ADU regulations.
State-Exempt ADU: All homeowners can build at least an 800 sq. ft., 16 ft.-tall ADU regardless of lot size, lot coverage, front setbacks, or neighborhood design standards. These are referred to as "66323 units" based on the Government Code. Parking is not required for state-exempt ADUs.
Owner-Occupancy: Not required, except for JADUs (Junior ADUs).
Height Limits:
16 ft. for all ADUs.
18 ft. for ADUs on multi-family properties or within half a mile walking distance of public transit.
25 ft. or the height limit of the primary dwelling for attached ADUs.
Setbacks: Side and rear setbacks must be at least 4 ft.
Maximum Size:
Detached ADUs: Up to 1,200 sq. ft.
State law also mandates a minimum allowance of 850 sq. ft. (or 1,000 sq. ft. for ADUs with more than one bedroom).
Attached ADUs: Up to 50% of the existing structure's size, with a minimum of 800 sq. ft. allowed if 50% is less.
Parking Requirements: No parking is required if:
The ADU is within half a mile of public transit.
The ADU is in an architecturally or historically significant district.
The ADU is attached to the primary dwelling or another existing structure.
On-street parking permits are required but not offered to the ADU occupant.
A ride-share vehicle is located within one block of the ADU.
Additionally, garage conversions do not require replacement parking, making them an appealing option for many homeowners.
These statewide standards provide a solid foundation for adding an ADU to your property while ensuring consistency across California.
New ADU Bills in California
The following ADU bills have gone into effect in 2024 and 2025 in California.
AB 2533: Amnesty program with a new and easier approval process for unpermitted ADUs.
SB 1211: Increases allowed quantity of detached ADUs for multi-family properties.
SB 1077: Initiated a new program to simplify the permitting process for ADUs in Coastal Zones
AB 3057: California Environmental Quality Act (CEQA) exemption is extended to junior accessory dwelling units (JADUs)
AB 2553: Transit stop has been redefined to include bus stops with 20 minutes or less of headway
SB 450: Cleanup Bill for SB 9
AB 976: Owner occupancy requirement is permanently eliminated
Let’s get into the details of these new bills and how they apply to your ADU project.
AB 2533 Unpermitted ADU Amnesty
California is already fairly lenient when it comes to unpermitted ADUs, but AB 2533 makes it even easier to legalize an ADU.
Prior to this bill, unpermitted ADUs needed to be brought up to current safety and building codes. AB 2533 changes that by removing the requirement to comply with non-safety-related building codes, as long as the ADU meets basic safety standards for habitable spaces. For instance, while current codes require new roofs to support solar panels, this is not a safety issue and can no longer be enforced as a condition for approval.
Additionally, AB 2533 mandates that cities provide a clear checklist of safety requirements that will be evaluated during the legalization process.
Finally, your city is prohibited from requiring you to pay impact, connection, or capacity fees if there are no infrastructure changes to the ADU.
SB 1211 ADUs on Multi-Family Properties
This is a BIG bill for housing density. SB 1211 increases the maximum allowed quantity of detached ADUs on a multi-family property.
Previously, all multi-family properties were limited to a maximum of two detached ADUs, regardless of the property size or the number of existing units.
With the new regulations, you can now build one detached ADU for each existing unit on the property, up to a maximum of eight.
These detached ADUs are allowed in addition to ADUs that are converted from existing spaces within the main dwelling.
To clarify, your property does not have to be zoned for multi-family use. As long as there is more than one living unit on your property, like a duplex, you can take advantage of this new regulation.
SB 1077 ADUs Simplified in Coastal Zones
Anyone that has property in a coastal zone and has tried to build an ADU may have been met with some hefty obstacles. SB 1077 requires the California Coastal Commission (CCC) and the Department of Housing and Community Development (HCD) to collaborate in providing local governments with a comprehensive set of guidelines to streamline ADU approvals in coastal zones. This must be completed by July 1st, 2026.
We’re still a ways off from seeing anything concrete, but gears are already turning towards a positive change in the current process.
AB 3057 JADUs Exemption from CEQA
The California Environment Quality Act (CEQA) applies to any project that causes a direct physical change in the environment, like a new construction project. The individuals or parties behind these projects are required to disclose those potential impacts to the public.
Originally, only ADUs were exempt from CEQA, but AB 3057 clarifies that junior accessory dwelling units (JADUs) are also exempt. AB 3057 is essentially a “clarification” bill.
AB 2553 Major Transits Redefined
AB 2553 doesn’t pertain to ADUs directly, but it still has a big impact on them.
AB 2553 expands the definition of "major transit stops" to include any bus stop with a service frequency of 20 minutes or less. Previously, the threshold was 15 minutes, which excluded many properties from qualifying for the benefits associated with being near a major transit stop.
What benefits? There are two main ones for ADUs located within half a mile walking distance from a major transit stop:
Parking is not required.
ADU can be up to 18 ft in height.
It’s interesting to see how much a five minute difference can make.
SB 450 Cleanup for SB 9
SB 450 will enhance the effectiveness of SB 9 in California by simplifying and accelerating the approval process for housing projects. Key changes include the removal of the 25% demolition limit for fast-tracked approvals, which means developers can demolish more of an existing structure without losing ministerial approval status. This is particularly beneficial for SB 9 projects, which often involve significant alterations to existing homes.
A 60-day approval deadline for cities will also help speed up SB 9 projects, providing a more predictable timeline for developers. Moreover, the bill clarifies rules for urban lot splits, directly supporting SB 9’s aim to divide single-family lots for multi-unit development.
Starting Your ADU in 2025
With over 85 ADUs built and thousands more supported through my educational YouTube Channel, I know how to streamline your project from start to finish. Sign up today for a free consultation and get the expert advice you need to make your ADU project a reality. Let’s get to work.
Commentaires