AB 956 allows a new two-detached-ADU pathway from January 1, 2027. Compare current rules, JADU limits and SB 1117 fees before planning your site.
Yes, California has signed a new two-detached-ADU law. AB 956 takes effect on January 1, 2027. It expands the qualifying single-family detached ADU pathway from one newly built unit to two. It is not already effective in October 2026, and it does not make every proposed layout permit-ready.
The question âCan I build two ADUs in California?â now needs a date and a description of the units. A garage conversion plus a backyard cottage is different from two newly built cottages. A junior ADU, or JADU, is another category.
This guide separates the current framework from AB 956's upcoming change, explains the related SB 1117 impact-fee rule, and provides a checklist for comparing prefab ADU options against a property's approval path.
1. What AB 956 changes on January 1, 2027
The Governor's September 29, 2026 signing announcement includes AB 956 and SB 1117. AB 956 is Chapter 791, Statutes of 2026. Its central change is to Government Code §66323(a)(2): two detached, newly constructed ADUs can qualify on a lot with an existing or proposed single-family dwelling, replacing the one-unit requirement in that paragraph.
Under this route, each detached unit can be subject to an 800-square-foot livable-space limit, the applicable statutory height limit and side/rear setbacks of up to four feet. Those parameters describe this particular state pathway, not every ADU route or a universal maximum unit size.
Read the chaptered AB 956 text, reproduced by CALege, especially §66323(a)(2) and (b). California YIMBY, the bill's sponsor, also explains the two-detached-unit purpose. The October 22 legal analysis from Best Best & Krieger confirms the January 1, 2027 effective date.
2. Two ADUs does not always mean two new backyard buildings
| Property / timing | Core §66323 combination | What to remember |
|---|---|---|
| Single-family lot, current 2026 framework | One qualifying conversion ADU + one new detached ADU + one JADU. | These are two full ADUs and a separate junior unit, in addition to the primary home. |
| Single-family lot, from January 1, 2027 | The new two-detached-unit pathway can combine with a qualifying conversion ADU. | A JADU is not also a mandatory approval when two new detached ADUs have been constructed under this route. |
| Existing multifamily property | Up to eight detached ADUs, not exceeding the existing dwelling count; eligible non-livable-space conversions are a separate category. | This is the multifamily rule, not AB 956's single-family change. |
| Proposed multifamily property | Up to two detached ADUs under the applicable multifamily route. | Do not apply the existing-multifamily eight-unit allowance to a proposed building. |
This table summarizes selected §66323 routes. It is not an all-parcel entitlement calculation or a universal ceiling across other statutory and local programs.
For the current framework, Placer County's June 2026 guidance illustrates the conversion + detached ADU + JADU combination. HCD's March 2026 ADU Handbook, pages 16â18, explains the categories and combinations.
The JADU tradeoff matters
AB 956 expressly says an agency is not required to approve a JADU on the same lot where two detached, newly constructed ADUs have been constructed under §66323(a)(2). Avoid planning on âtwo new cottages plus a JADUâ as an unconditional state entitlement. If a JADU or ADU already exists, have the agency identify how it counts before designing additional units.
There may be another route beyond this table
HCD's March 2026 Handbook, page 18, also says a local agency must allow at least one §66314 unit in addition to §66323 units, with permitted objective standards applying to that route. This is a reason to request a route-by-route assessment. It should not be simplified into a promise that every parcel can accommodate a fixed total number of homes.
3. What is a JADU, and why is it counted separately?
A JADU is limited to 500 square feet of interior livable space and is contained within a single-family residence, including eligible attached-garage space. It is not simply a smaller detached cottage.
AB 1154's changes took effect January 1, 2026: owner occupancy is required where the JADU shares sanitation facilities with the primary structure, but not where it has separate sanitation facilities. JADU rentals must be longer than 30 days. HCD discusses these distinctions in its Farmersville findings letter and 2026 Handbook.
4. SB 1117 changes the impact-fee calculation
SB 1117, Chapter 809, Statutes of 2026, also takes effect January 1, 2027. Under its amended §66311.5(c), an ADU with 750 square feet or less of interior livable space remains exempt from impact fees. For a lot with up to two ADUs, a larger unit's proportionate impact-fee calculation uses only the area above 750 square feet.
Area example, not a price quote: for a 1,000-square-foot ADU on a qualifying lot, the area used by the new excess-area rule is 1,000 â 750 = 250 square feet. The actual charge still depends on the applicable fee schedule and statutory proportional calculation.
On a property with more than two ADUs, the statute retains proportional calculation using the larger ADU's full area. That distinction matters if you are comparing a two-ADU plan with a three-ADU configuration.
Impact fees are not the entire permit or construction budget. The statute expressly excludes utility connection fees and capacity charges from its impact-fee definition. Do not interpret âimpact-fee exemptâ as âno fees.â Review the chaptered SB 1117 text reproduced by CALege and request an itemized written estimate.
5. Existing multifamily homes follow different rules
SB 1211's expansion took effect in 2025, rather than being a new 2027 benefit. HCD's Pasadena findings letter describes the distinction: existing multifamily lots may qualify for up to eight detached ADUs, capped by the existing dwelling count; proposed multifamily lots have a different two-unit allowance.
For example, an existing four-unit multifamily property does not receive eight detached ADUs under that clause: the existing-unit cap matters. Conversions of qualifying non-livable space inside an existing multifamily structure have their own allowance of at least one unit and up to 25% of existing units. Confirm the property's classification and the proposed combination.
6. A permit pathway is not a construction timetable
SB 543 introduced a 15-business-day application completeness determination, summarized in HCD's April 2026 housing-law fact sheets. A completeness check does not mean an ADU will be approved, built or connected to utilities within 15 business days.
Likewise, ministerial review removes discretionary judgment; it does not remove building-code review. Ask the team to distinguish the application, approval, utility, construction and occupancy milestones in its schedule.
AB 956 also broadens protections against private restrictions on lots zoned to allow single-family residential use. Reasonable restrictions remain possible. Do not assume all HOA documents are irrelevant or that an HOA review substitutes for a building permit.
7. What to check before choosing a prefab ADU
- Inventory the parcel. Record the primary dwelling, existing ADUs/JADUs and permitted accessory structures.
- Name each approval route. Ask the planner to identify the subsection for each proposed unit and the effective law at review.
- Compare two site concepts. Test a conversion-plus-cottage layout against a two-new-cottage layout, including privacy and access.
- Review buildability. Coordinate easements, foundations, drainage, utility routes, fire/life-safety requirements and delivery access.
- Price the complete scope. Separate building package, local site work, permits, connections and impact fees.
- Obtain the counting decision in writing. Address existing units, any JADU and any additional §66314 route before ordering.
Prefab describes off-site production, not a land-use entitlement. Panelized, volumetric modular and manufactured systems have different definitions and workflows. XHOME Signature Homes and ADUs use a panelized approach. Our panelized vs. modular guide explains the construction distinction; our California ADU electrical planning guide covers related utility questions.
SB 9 lot splits are another framework. Do not add their unit counts to this table without a separate analysis of the lot-split rules.
Frequently asked questions
Can I build two detached ADUs right now?
AB 956's expanded §66323 route starts January 1, 2027. Before then, assess existing state pathways and any more permissive local rules. Signing a bill and reaching its effective date are different events.
Can each of the two detached ADUs be 1,200 square feet?
Do not assume so. The AB 956 §66323(a)(2) pathway allows an 800-square-foot livable-space limitation on each unit. Larger designs require analysis of another applicable route.
Does two ADUs mean two more units if I already have one?
No automatic âtwo extraâ entitlement follows from that phrase. Inventory the existing unit and have the agency confirm how it is classified and counted.
Does AB 956 guarantee approval of a particular XHOME model?
No. The model, design documents, site and proposed unit combination still need to satisfy the applicable requirements. Confirm product dimensions and scope for the selected project.
Planning a California ADU project for 2027?
Discuss your site with XHOME. Share the city or county, existing structures and intended unit mix so the first conversation can focus on a feasible panelized home plan and clearly assigned local work.
Research date: October 28, 2026. General planning information; confirm parcel-specific application with the permitting agency and qualified project advisers. Direct California Legislative Information pages were unavailable during this review; chaptered text was cross-checked through a public reproduction, the Governor's signing release, the bill sponsor and municipal-law analysis. The March 2026 HCD Handbook predates AB 956's September signing.
Cover: AI-generated conceptual residential-site illustration. It is not a survey, compliant site plan, permit approval or actual XHOME project.
