California AB 956 Explained: Two Detached ADUs, the JADU Trade-Off, and What It Means for Your Home’s Value

Starting January 1, 2027, California homeowners with a single-family house can build two freestanding ADUs in the backyard, and the city must approve them if they meet state standards. The trade-off: choosing two detached units means your city no longer has to approve a junior ADU inside the house. Here is what the law says, what it does to your home’s value, and how to decide which layout fits your lot.

What is California AB 956?

California AB 956 requires cities and counties to approve two detached, new-construction ADUs on a lot with a single-family home, up from one. Governor Newsom signed it on September 29, 2026, as Chapter 791, Statutes of 2026.

The bill was authored by Assemblymember Sharon Quirk-Silva of Fullerton and sponsored by California YIMBY, a pro-housing advocacy group. It passed the Senate 27–6 and cleared its final Assembly vote 60–2 in August 2026, according to the LegiScan bill history.

The law changes three sections of state code. It rewrites Government Code Section 66323, the list of ADUs every city must approve, and amends Civil Code Sections 714.3 and 4751, which limit what deed restrictions and HOAs can do to block ADUs.

“Must approve” has a specific meaning here. The Assembly’s own analysis describes AB 956 as allowing streamlined and ministerial approval of up to two detached ADUs: staff check your plans against objective rules, with no public hearing and no neighbor veto. Under existing state law, the city has 60 days to act on a complete ADU application.

When does AB 956 take effect?

AB 956 takes effect January 1, 2027. It applies to every city and county directly, so you do not have to wait for your local ADU ordinance to be rewritten.

The bill text sets no special start date, so California’s default rule applies: regular-session statutes become effective on January 1 after they are enacted. Until then, the state only guarantees one new detached ADU on a single-family lot, though some cities already allow more.

The obligation sits in state Government Code Section 66323, which overrides conflicting local rules for the units it covers. Expect some cities to lag in updating their handouts and forms during 2027. If a planner quotes the old limit after January 1, ask them to confirm against the amended statute.

A companion bill signed the same day also starts January 1, 2027. SB 1117 (Chapter 809, Statutes of 2026) changes how impact fees are charged on larger ADUs, covered in the cost section below.

What changed from the old California ADU law?

The guaranteed number of new detached ADUs on a single-family lot rises from one to two. The guaranteed total stays at about four homes per lot, because a second detached unit replaces the junior ADU rather than adding to it.

Before AB 956, state law guaranteed a mix of one detached ADU, one conversion ADU, and one junior ADU on a single-family lot. San Diego’s regional planning agency summarized the same rule in its 2025 guidance, which interprets the state ADU handbook: one newly built detached ADU, one ADU converted from existing space, and one junior ADU.

The chaptered text of AB 956 changes the detached count to two and adds one exception: the city does not have to approve a junior ADU on a lot where two new detached ADUs have been built. It also widens HOA protections, explained below.

Rule	Before Jan. 1, 2027	After Jan. 1, 2027 (AB 956)
New detached ADUs guaranteed	1	2
Conversion ADU (garage, existing space)	1	1
Junior ADU (inside the house, max 500 sq ft)	1	1, but not guaranteed if you build 2 detached
Guaranteed homes on the lot, including the house	Up to 4	Up to 4
Size cap cities may set on a detached ADU	No lower than 800 sq ft	No lower than 800 sq ft
Side and rear setbacks cities may require	No more than 4 ft	No more than 4 ft
HOA/CC&R protection applies to	Lots “zoned for” single-family use	Lots “zoned to allow” single-family use
Impact fees on ADUs over 750 sq ft	Proportional to the whole unit	Charged only on area above 750 sq ft (SB 1117)

Sources for the table: AB 956 chaptered text, SB 1117 bill record, and the Assembly Local Government analysis.

How big and how tall can each ADU be under AB 956?

On the guaranteed path, your city may cap each detached ADU at 800 square feet of living space, 16 feet tall in most places, with side and rear setbacks of no more than 4 feet. Many local ordinances allow larger units.

The AB 956 text lists only two conditions a city can place on these detached units: a floor-area limit of no less than 800 square feet and the height limits in Government Code Section 66321. The city cannot add other objective design standards to units that qualify, and cannot make you fix older nonconforming conditions on the property as a condition of approval.

Under Section 66321, a city must allow at least 16 feet for a detached ADU. That rises to 18 feet within a half-mile walk of a major transit stop or high-quality transit corridor, plus 2 more feet when the ADU’s roof pitch matches the main house.

The 800-square-foot figure is a floor on what cities may cap, not a ceiling on what you can build. The same code section bars local size limits below 850 square feet, or 1,000 square feet for an ADU with more than one bedroom, for ADUs approved under a city’s own ordinance. Ask your planning department which path applies to each of your two units before you finalize floor plans.

A few other rules carry over. The chaptered statute requires rentals longer than 30 days, bars a fire-sprinkler requirement when the main house does not need sprinklers, and lets septic-served lots be asked for a recent percolation test.

Can I still add a JADU if I build two detached ADUs?

Not as a guaranteed right. Once two new detached ADUs are built on the lot, your city is not required to approve a junior ADU, though it may still choose to.

This exception was added late in the bill’s life and is missing from much of the coverage written in 2025. The chaptered text says a local agency is not required to approve a JADU on the same lot where two detached, new-construction ADUs have been constructed. A junior ADU is a unit of no more than 500 square feet contained entirely within the single-family home.

Read together, the statute’s list of guaranteed units gives you two combinations you can count on:

1. The house, one conversion ADU, one JADU, and one detached ADU. This was the pre-2027 maximum and remains available.
2. The house, one conversion ADU, and two detached ADUs. This is the new option AB 956 creates.

Both reach four homes on one lot. Some cities allow more under their own ordinances, so confirm with your planning department before you design around either combination.

Is two detached ADUs or one ADU plus a JADU better for my home’s value?

Two detached units usually suit owners with a deep, flat yard who want two independent rentals. One detached ADU plus a JADU or garage conversion usually suits owners with an underused garage or spare rooms, because converting existing space avoids a second foundation and roof.

The value research below measures ADU presence, not specific layouts, so no study yet shows which combination appraises higher. A Los Angeles study of assessed values and sale prices found ADU presence raised value by 7% to 9%; how much a second detached unit adds on top of the first has not been measured.

These questions usually decide it:

• Space: Can two 800-square-foot buildings fit with 4-foot side and rear setbacks, a walkway to each, and room for utility runs?
• Existing structure: Do you have a garage or attached space a conversion ADU or JADU could use?
• Use: Do you want two fully separate rentals, or a unit for family plus one rental?
• Utilities: Can your water, sewer, and electrical service carry three or four households, and what will your providers charge for new connections?
• Privacy: A JADU shares walls with your house; a detached unit does not.

Can my HOA stop me from building two ADUs?

No, if the units meet state ADU law. AB 956 voids CC&Rs that prohibit or unreasonably restrict ADUs on any lot zoned to allow single-family use; HOAs can still set reasonable rules.

California already barred deed restrictions and HOA governing documents from blocking ADUs, but only on lots “zoned for” single-family residential use. According to the bill’s sponsor, that wording left out owners whose single-family homes sit on land zoned for multifamily housing. AB 956 rewrites Civil Code Sections 714.3 and 4751 to cover any lot “zoned to allow” single-family use.

The statute still lets an HOA impose reasonable restrictions, and it defines that term narrowly. Under the amended Civil Code text, a reasonable restriction cannot unreasonably raise the cost of building an ADU, effectively prohibit it, or wipe out your ability to build one that complies with state law. Section 714.3 adds that fees and other financial requirements do not count as reasonable restrictions.

In practice, an HOA can usually still weigh in on matters like exterior colors or materials, as long as its rules do not make a code-compliant ADU impossible or unreasonably expensive. If your association denies an application outright, get the denial in writing and compare its reasons against these Civil Code sections before you revise your plans.

How much value does an ADU add to a California home?

The best peer-reviewed estimate is 7% to 9%: in Los Angeles, ADU presence raised assessed value and sale price by that much. The widely quoted “50%” figure comes from an earlier, unpublished working paper.

UC Irvine economists Jan Brueckner and Sarah Thomaz studied Los Angeles parcel data and found that ADU presence raises a parcel’s assessed value and selling price by 7% to 9%. The study was published in Real Estate Economics in 2024.

The larger number traces to Thomaz’s earlier job-market paper, which used a different statistical method and estimated that an ADU raises property value by about 50% on average. That was a working paper; the later peer-reviewed study reports the much smaller 7% to 9% effect. If you see “ADUs add 50%” in marketing, this is usually the source.

Federal appraisal data points the same direction. The Federal Housing Finance Agency reported that California’s median appraised value for homes with ADUs grew 9.34% a year from 2013 to 2023, versus 7.65% for homes without them. FHFA cautions that the difference needs further analysis and may reflect larger, higher-quality ADUs built after 2018.

How will an appraiser value a home with two ADUs?

Appraisers price a home against recent comparable sales, and California sales with even one ADU are still a small slice of the market. Two-ADU comparables will be scarcer still in 2027, which can make appraisals less predictable for buyers, sellers, and refinancing owners.

In FHFA’s appraisal data, only 2.9% of Fannie Mae- and Freddie Mac-backed purchase appraisals in California involved a property with an ADU in 2023. FHFA also notes that ADU data may contain appraiser entry errors, with some ADUs missed and some reported that do not exist.

Two things improve your odds. Keep complete permit and final-inspection records for every unit, because the appraiser needs to confirm each one is a legal dwelling. And give the appraiser your signed leases or market rent estimates, so the income the units can produce is documented.

Is it harder to sell a house with an ADU?

It depends on the market and the buyer. In high-cost areas, an ADU widens the pool to multigenerational households and buyers who want rental income; where few comparable sales exist, pricing it correctly is harder.

Listing data has shown wide swings. A 2021 Trulia analysis reported by RealTrends found homes with ADUs priced about 35% higher on average in large cities, while in Berkeley the average listing with an ADU was 41% below the city’s average listing price. Those are list-price averages, not controlled comparisons, so treat them as a sign that local conditions dominate.

Adding ADUs also affects carrying costs. Under Proposition 13, only the new construction is assessed at market value and added to your existing base; the house and land are not reassessed. A buyer will see a higher tax bill than the original home alone, so factor it into rent and resale math.

How much does an ADU cost in California, and are grants available in 2026?

Build costs vary too much by site, size, and builder for one reliable statewide number, so get at least two site-specific bids. Two state rules cut the fee portion, and the CalHFA grant of up to $40,000 has been fully allocated since December 2023.

Impact fees are the part state law controls. ADUs of 750 square feet or less pay no impact fees, and larger ADUs have been charged in proportion to the main house. Starting January 1, 2027, SB 1117 limits that charge to the area above 750 square feet, so an 800-square-foot ADU is assessed on 50 square feet rather than all 800.

The sponsor’s summary says this marginal rule applies to the first two ADUs on a property, with additional ADUs assessed on their full size. Supporters estimated impact fees of $10 to $30 per square foot in some communities, which is why the change matters on a two-unit project. Water and sewer connection fees are a separate line item, so ask your providers early.

The state’s best-known subsidy is not currently available. CalHFA’s ADU Grant Program reimbursed up to $40,000 in pre-development and closing costs, but the agency posted on December 28, 2023, that the latest round was fully allocated. The same page warns that anyone offering to get you an ADU grant is running a scam.

AB 956 vs. SB 9: which law fits my property?

Use AB 956 if you want rental or family units on one lot you keep. Use SB 9 if you want to split the land into separately sellable parcels and can commit to living there for three years.

SB 9, signed in 2021, lets owners subdivide a single-family parcel into two lots and build a two-unit project. AB 956 never divides the land: the house and the ADUs stay on one parcel with one deed.

Question	AB 956 (two detached ADUs)	SB 9 urban lot split
What you get	Up to 4 homes on one lot	2 lots, with up to 2 units each
Sell units separately?	No, except where a city has opted into ADU condo sales	Yes, each new lot can be sold
Owner-occupancy rule	None for ADUs	3-year owner-occupancy affidavit
Where it applies	Lots with a single-family home in residential or mixed-use zones	Single-family zones in urbanized areas, with exclusions
Approval	Building permit	Parcel map, then building permits
Minimum new lot size	Not applicable	1,200 sq ft, unless the city allows smaller

The SB 9 terms come from Government Code Section 66411.7, which requires a lot-split applicant to sign an affidavit of intent to live in one unit for at least three years and caps each resulting parcel at two units, ADUs included. The same section bars lot splits that would demolish or alter housing occupied by a tenant in the last three years. State ADU law, by contrast, prohibits cities from requiring owner occupancy for an ADU.

For most owners who want income or room for family, AB 956 is the simpler path. SB 9 is the tool when your goal is to create land you can sell or finance on its own.

What should homeowners do before January 1, 2027?

Plan for two units even if you build one now: place the first ADU so a second can fit, size utilities for both, and ask your planning department how it will process AB 956 applications.

1. Map the lot. Sketch two 800-square-foot footprints with 4-foot side and rear setbacks, a path to each door, and the sewer and water routes. If they do not fit, the one-ADU-plus-JADU layout is your realistic option.
2. Talk to your planning department. Ask whether its ordinance allows units larger than the state’s 800-square-foot guaranteed size, and how it will handle applications that rely on AB 956 after January 1, 2027.
3. Call your utility providers. Connection fees for detached units are separate from impact fees, and a two-unit project can need a larger water meter, sewer lateral, or electrical panel.
4. Check your HOA documents. Compare any ADU rules against the amended Civil Code Sections 714.3 and 4751 before you submit plans to the association.
5. Run the value math. Compare build cost against realistic rent and the 7% to 9% value effect measured in Los Angeles, not marketing figures.
6. Read the state handbook. HCD’s ADU Handbook and its 2026 addendum cover the rest of state ADU law, and HCD says it will update the handbook’s FAQs.