Updated October 2026. We keep this page current as new ADU laws take effect, so you don’t have to piece the rules together from a separate article for each year.
Two more ADU laws take effect on January 1, 2027. AB 956 lets you build two detached ADUs on a single-family lot instead of one, and SB 1117 means a larger ADU only pays impact fees on the space above 750 square feet. Both are covered below, along with other rules on the way in California and the Los Angeles area.
California’s ADU laws also changed on January 1, 2026. In short: size limits now count interior livable space, small ADUs skip more fees, a junior ADU with its own bathroom no longer requires you to live on the property, and cities face tighter deadlines. The 2024 and 2025 changes still apply too, including the right to legalize an older unpermitted ADU and, where your city allows it, to sell an ADU separately.
California ADU Laws at a Glance
| Law | In effect | What it means for homeowners |
|---|---|---|
| AB 956 | January 1, 2027 | Cities must approve up to two detached, new construction ADUs on a lot with a single-family home, each up to 800 sq ft with 4-foot side and rear setbacks. A city does not also have to approve a junior ADU on a lot that has two detached ADUs. |
| SB 1117 | January 1, 2027 | For the first two ADUs on a lot, impact fees on an ADU over 750 sq ft can only be charged on the square footage above 750. ADUs of 750 sq ft or less still pay no impact fees. |
| SB 543 | January 1, 2026 | ADU size limits are measured in interior livable space. ADUs of 750 sq ft or less and JADUs of 500 sq ft or less pay no impact fees, and units of 500 sq ft or less pay no school fees. Cities must tell you within 15 days whether your application is complete. |
| AB 1154 | January 1, 2026 | A junior ADU only requires the owner to live on the property if it shares a bathroom with the main home. ADUs and JADUs can’t be rented for 30 days or less. |
| SB 9 (2025) | January 1, 2026 | A city’s ADU ordinance is void if the city doesn’t send it to the state housing department (HCD) within 60 days of adopting it. This is a different bill from the 2021 SB 9 lot-split law. |
| AB 462 | October 10, 2025 | Coastal cities and the Coastal Commission must decide an ADU’s coastal development permit within 60 days, and a city’s decision can’t be appealed to the Commission. Where a state of emergency was declared on or after February 1, 2025, an ADU can be occupied before a destroyed home is rebuilt. |
| AB 2533 | January 1, 2025 | An unpermitted ADU or JADU built before January 1, 2020 can usually be legalized by meeting health and safety standards, with no penalties or impact fees. |
| SB 1211 | January 1, 2025 | Multifamily properties can add up to eight detached ADUs, as long as that doesn’t exceed the number of existing units. Cities can’t require replacement parking when uncovered spaces are removed for an ADU. |
| AB 1332 | January 1, 2025 | Cities must offer a preapproved ADU plan program, and an application that uses a preapproved plan gets a faster decision. |
| SB 1077 | January 1, 2025 | The Coastal Commission and HCD published guidance for ADU permitting in the coastal zone on July 1, 2026. |
| AB 976 | January 1, 2024 | Cities can never require you to live on the property to build or rent an ADU. |
| AB 1033 | January 1, 2024 | Cities may let homeowners sell an ADU separately as a condominium. It only applies where your city has opted in. |
What Changes in 2027
AB 956: two detached ADUs on a single-family lot
Starting January 1, 2027, your city has to approve two new detached ADUs on a lot with a single-family home, up from one. Each can be up to 800 square feet of livable space with 4-foot side and rear setbacks, and each gets the same ministerial (no hearing) approval the single detached ADU gets today. There is one trade-off: once you build two detached ADUs, the city does not also have to approve a junior ADU on that lot.
Lot size and layout still decide whether two units fit, so read our guides on how to position an ADU on your property and ADU setback requirements before you plan for two. Your city has to follow AB 956 from January 1, even if it has not rewritten its own ADU ordinance yet. AB 956 also extends the state ban on HOA rules that block ADUs to single-family homes on lots zoned for multifamily use. Read the full text of AB 956.
SB 1117: lower impact fees on larger ADUs
Starting January 1, 2027, a city can only charge impact fees on the part of an ADU above 750 square feet, for the first two ADUs on a lot. Impact fees are one-time charges cities put on new units to help pay for parks, roads, and other services. Today, many cities charge a larger ADU these fees on its entire floor area, so a 1,000 square foot ADU pays on all 1,000 square feet. Under SB 1117, that same ADU pays on 250. The fee is still scaled to the size of your main home, and ADUs of 750 square feet or less still pay nothing.
SB 1117 also applies to charter cities like Los Angeles, which can otherwise set some of their own rules. It covers impact fees only. Utility connection fees and school fees follow their own rules, so ask for a full fee estimate early. Read the full text of SB 1117.
Other 2026 laws that affect home projects
AB 1621 limits cities to two rounds of plan check (the city’s review of your construction drawings) on a building permit for a housing project. After two rounds, the city can deny a noncompliant application, and you can resubmit. Ask your designer whether your city applies it to ADU permits.
SB 908 requires cities to approve window replacement permits without a hearing, and voids HOA rules that effectively block window replacement. Buildings on historic registers are exempt.
SB 222 targets heat pump upgrades in existing homes. Starting July 1, 2027, cities must offer inspections for heat pump water heaters and heat pump HVAC that do not require the contractor and inspector to be on site at the same time. Plug-in window units will not need a permit, and HOA bans on heat pumps become void.
What Could Change Next
Some of these are still in draft, and others are already law but will not take full effect for a while. All of them are worth watching if you are planning an ADU in Southern California.
- An updated state ADU Handbook. HCD last updated its ADU Handbook in March 2026 for the 2026 laws. We expect a revision that covers AB 956 and SB 1117.
- Unincorporated LA County. The County is drafting a 2026 ADU ordinance amendment after the state housing department found its current ordinance out of line with state law. No hearings are scheduled yet. If you are in an unincorporated area, including Altadena, check the draft before you finalize plans.
- Altadena rebuilds. SB 1090, in effect now, pauses the no-hearing, streamlined approval path for certain larger housing projects and lot subdivisions in Altadena through January 1, 2030. If you are rebuilding after the Eaton Fire and want an ADU, confirm how it applies to your lot with LA County. Our Eaton Fire recovery guide covers the rest of the rebuild process.
- Remote inspections and prefab. AB 1738 will require cities to offer remote inspections for specified work on one- and two-family homes, starting in 2028. AB 2058 will let owners of factory-built homes choose a third-party inspector once HCD writes the rules, which are due by January 1, 2029.
What Changed in 2026
SB 543: size, fees, and faster answers
SB 543 cleans up how ADU rules are applied. Size limits are now measured in interior livable space. The impact fee exemption is spelled out: no impact fees on an ADU of 750 square feet or less or a JADU of 500 square feet or less, and no school fees on units of 500 square feet or less. Cities also have to tell you within 15 days whether your application is complete, and they need a written appeal process if they deny it.
AB 1154: junior ADUs and owner-occupancy
A junior ADU is a unit of up to 500 square feet built inside your home. Until 2026, you had to live on the property to have one. Now the owner-occupancy rule only applies when the JADU shares a bathroom with the main home. Give it its own bathroom and you can rent both the house and the JADU. AB 1154 also confirms that ADUs and JADUs can’t be used as short-term rentals of 30 days or less.
AB 462: coastal permits and fire rebuilds
AB 462 took effect immediately in October 2025. Cities in the coastal zone have to approve or deny an ADU’s coastal development permit within 60 days, and a city’s decision can no longer be appealed to the Coastal Commission. When the Commission itself is the permitting agency, it has the same 60 days, and an application it doesn’t act on is deemed approved. In counties where the Governor declared a state of emergency on or after February 1, 2025, an ADU can get its certificate of occupancy before a substantially damaged or destroyed home is rebuilt, which lets families move back onto their lot sooner. AB 462 does not exempt ADUs from needing a coastal permit; it puts a clock on the decision. In the Palisades burn area, the City of Los Angeles also lets a detached ADU be built with or before the rebuilt home, and our Palisades Fire recovery guide explains the rest.
SB 9 of 2025: cities have to file their rules
This is not the 2021 SB 9 that allows lot splits. The 2025 bill says a city’s ADU ordinance is void if the city doesn’t send it to HCD within 60 days of adopting it. If your city’s rules are void, state ADU law applies directly.
The 2025 Changes That Still Matter
AB 2533 is the one most homeowners ask us about. If an ADU or garage conversion was built without permits before January 1, 2020, you can usually legalize it by meeting health and safety standards rather than bringing everything up to current code, and the city can’t charge penalties or impact fees. Our guide to legalizing an unpermitted ADU under AB 2533 walks through the process.
SB 1211 opened up multifamily properties: up to eight detached ADUs, capped at the number of existing units, and no replacement parking when uncovered spaces are removed. AB 1332 requires every city to offer preapproved ADU plans, which shortens review. SB 1077 required state guidance for ADUs in the coastal zone, which the Coastal Commission published on July 1, 2026.
The 2024 Changes: Owner-Occupancy and Selling an ADU
AB 976 made the ban on ADU owner-occupancy requirements permanent, so you can rent both your home and your ADU. AB 1033 lets cities allow an ADU to be sold separately as a condominium. It only works where a city opts in. The City of San Diego is one of them, which is covered on our San Diego ADU page.
The Core ADU Rules Every California Homeowner Gets
- A detached ADU can be up to 1,200 square feet, and every city must allow at least 800 square feet.
- Starting in 2027, a single-family lot can have two detached ADUs of up to 800 square feet each.
- A junior ADU can be up to 500 square feet inside the main home.
- Cities must approve or deny a complete ADU application within 60 days, or it is deemed approved.
- Side and rear setbacks can’t be more than 4 feet.
- ADUs of 750 square feet or less pay no impact fees. Starting in 2027, larger ADUs only pay on the space above 750 square feet.
- You don’t have to live on the property, unless it is a junior ADU that shares a bathroom with the main home.
- ADUs can’t be rented for 30 days or less.
Your city can add its own rules on top, such as design standards or height limits, as long as they don’t conflict with state law. That is why the same ADU can be simple in one city and slow in the next.
Planning an ADU Under the New Rules?
The laws keep making ADUs easier to permit, but they don’t make the build any simpler. A contractor who has permitted ADUs in your city will know which of these rules your city actually applies and where plan check tends to stall. GreatBuildz matches you with three vetted ADU contractors for free, including specialists in garage conversions, and stays involved until final inspection. For budgeting, start with our ADU cost guide.
Frequently Asked Questions
What are the new ADU laws in California for 2027?
Two take effect on January 1, 2027. AB 956 requires cities to approve up to two detached, new construction ADUs on a lot with a single-family home, up from one. SB 1117 limits impact fees on an ADU over 750 sq ft to the square footage above 750, for the first two ADUs on a lot.
Can I build two ADUs on my property in California?
Starting January 1, 2027, yes, if your lot has room. AB 956 requires cities to approve two detached ADUs of up to 800 sq ft each, with 4-foot side and rear setbacks, on a lot with a single-family home. If you build two detached ADUs, the city does not also have to approve a junior ADU.
What are the new ADU laws in California for 2026?
Three took effect on January 1, 2026. SB 543 measures ADU size by interior livable space, confirms that ADUs of 750 sq ft or less pay no impact fees, and requires cities to confirm a complete application within 15 days. AB 1154 limits the JADU owner-occupancy rule to JADUs that share a bathroom with the main home. SB 9 of 2025 voids any city ADU ordinance not sent to the state within 60 days of adoption.
How big can an ADU be in California?
A detached ADU can be up to 1,200 square feet of interior livable space, and every city must allow at least 800 square feet. A junior ADU, built inside the main home, can be up to 500 square feet.
Do I have to live on the property to build an ADU in California?
No. Since AB 976 took effect in 2024, cities can’t require owner-occupancy for an ADU. The only exception left is a junior ADU that shares a bathroom with the main home, under AB 1154.
Can I legalize an unpermitted ADU in California?
Usually, yes. Under AB 2533, an ADU or JADU built without permits before January 1, 2020 can be legalized by meeting health and safety standards rather than every current code, and the city can’t charge penalties or impact fees to do it.
Can you sell an ADU separately in California?
Only where your city has opted in. AB 1033 lets cities allow an ADU to be sold as a separate condominium. The City of San Diego adopted it in 2025 and unincorporated San Diego County in 2026, but most cities have not.
