California ADU laws 2027: AB 956 and SB 1117

California ADU laws 2027 at a glance

Governor Newsom signed a package of housing bills on September 29, 2026. Two of them change ADU law. Like most California statutes, they take effect on January 1 of the following year, so until then the 2026 rules in our guide to California ADU laws still apply.

The sections below take each bill in turn. Bill text is on the state's legislative site for AB 956 and SB 1117.

AB 956: two detached ADUs

Today, every city must approve a short list of ADUs on a single-family lot without discretion: one ADU converted from existing space, one new detached ADU of up to 800 square feet with 4-foot side and rear setbacks, and one junior ADU. AB 956 amends that section to raise the number of new-construction detached ADUs from one to two. The bill's record shows it was signed and chaptered in 2026.

The JADU trade-off

The added unit comes with a condition. Under the bill, a city isn't required to ministerially approve a junior ADU on the same lot where two detached, new-construction ADUs have been built. That's a permission for the city, not a ban on JADUs: a city may still allow one. Check your local ordinance once it's updated.

Size, height and setback guarantees for the detached units come from the same section of law. Today's guarantee is 800 square feet with 4-foot side and rear setbacks. Read the chaptered text, or wait for the state housing department's next handbook, before you design two units around exact square footage. See our guides to ADU setbacks and the ADU height limit in California for the current numbers.

AB 956 and HOAs

AB 956 also amends the Civil Code sections that void HOA rules and deed restrictions that effectively prohibit or unreasonably restrict ADUs. The protection now covers a lot zoned to allow single-family residential use, not only a lot zoned for single-family use. That matters for homes in zones that permit houses alongside other uses. Our guide to ADU HOA rules in California explains what an association can and can't still regulate.

SB 1117: impact fees above 750 sq ft

Impact fees pay for parks, roads and other public facilities. Current law bars them for an ADU of 750 square feet or less. Above that line, fees must be proportional to the size of the main house, and they apply to the whole unit. A 751-square-foot ADU pays on all 751 feet.

SB 1117 changes that. For an ADU over 750 square feet of interior livable space, impact fees apply only to the area above 750 square feet. According to the bill text, that method covers up to two ADUs on a lot; beyond two, the existing proportional method still applies. The Assembly's committee analysis notes the bill leaves the existing exemptions in place: none for an ADU of 750 square feet or less, or a JADU of 500 or less.

The bill doesn't set a dollar amount; the local fee is applied to a smaller base. The effect is to soften the jump at 751 square feet, where today the whole unit becomes chargeable. Utility connection fees and school fees follow their own rules; see what an ADU costs in San Diego for those. The bill's legislative record shows its votes and versions.

What doesn't change

Neither bill rewrites the rest of ADU law. The rules that took effect on January 1, 2026 stay in force:

• Permit clock. Fifteen business days to rule on completeness, then 60 days to approve or deny, or the permit is deemed approved.
• Owner occupancy. None for an ADU. For a JADU, only if it shares a bathroom with the house.
• Size measurement. Interior livable space, the measure SB 1117 uses for its 750-foot line.
• Parking. No parking near transit or for conversions, and no replacement parking for a converted garage. See ADU parking requirements.
• Multifamily lots. AB 956 is about single-family lots. Rules for apartment properties are in our multifamily ADU guide.

Building now or waiting

If you're planning an ADU this fall, the new laws can change your design:

• Want two backyard units? Plan for a permit decision under the 2027 rules. Until January 1, a second detached unit depends on your city's own ordinance.
• Designing between 750 and 1,200 square feet? SB 1117 shrinks the fee base on anything over 750. Ask your city when it will apply the new method and whether your permit date matters.
• Counting on a JADU and two detached units? Don't assume the city must approve all three. Ask first.
• Already in review? Talk to the city before you redesign mid-review to take advantage of either bill.

We don't yet know how each city will handle applications submitted in late 2026 but decided in 2027. That's a question for your permit office. An experienced builder will have asked it already; compare verified ADU builders in San Diego, and see how to hire an ADU contractor before you sign.

What it means in San Diego

In the City of San Diego, SB 1117 changes less than it does elsewhere. The city already exempts the first two ADUs on a property from development impact fees, whatever their size. That exemption covers development impact fees only, so other charges still apply.

AB 956 matters more. San Diego's ADU code allows ADUs from 150 to 1,200 square feet and caps total units on a single-family lot under its ADU Home Density Bonus at 4 to 6, depending on lot size, after the 2025 cutback. The city will need to reconcile its code with the new state floor. Until it does, ask Development Services how it will review a second detached ADU. Cities elsewhere in San Diego County will be amending their own ordinances on their own timelines.

Common questions