California ADU policy: 2026 rules and preparation for 2027

Effective rules versus newly signed legislation

Sources checked October 3, 2026. Relevant SB 543 and AB 1154 provisions took effect January 1, 2026. AB 956 and SB 1117, signed September 29, 2026, are non-urgency measures taking effect January 1, 2027 under the ordinary effective-date rule. Do not apply these future provisions to a current submission without checking timing and the authority’s implementation.

Review milestones are not a move-in schedule

Government Code §66317 provides 15 business days for a written completeness determination, with missing items identified. A complete ADU application on a lot with an existing home has a 60-day approval-or-denial period, subject to statutory exceptions such as concurrent new-home applications or applicant-requested delays. Design preparation, corrections, utilities and construction are separate. Retain receipts, completeness notices and a response log.

Impact fees: distinguish the fee category and floor-area measure

SB 543 exempts ADUs with 750 square feet or less of interior livable space and JADUs with 500 square feet or less from impact fees. Larger ADUs use proportional impact fees relative to the primary dwelling. Connection and capacity charges are excluded from that definition; permit, review and construction costs are not universally waived. School fees have separate provisions, including the less-than-500-square-foot assessable-space rule. Obtain itemized assessments before comparing layouts.

JADU bathrooms and occupancy

HCD explains that AB 1154 retains owner occupancy for a JADU sharing sanitation facilities with the primary home, but removes it where facilities are not shared. Rentals must exceed 30 days. A separate bathroom may offer flexibility while adding plumbing and layout work; compare the actual scope, not assumed returns.

Coming in 2027: AB 956

AB 956, Chapter 791, expands qualifying detached new-construction ADUs from one to two on a lot with a proposed or existing single-family home and revises certain covenant and HOA provisions. This is a future conditional pathway, not current permission for every lot. Study access, setbacks, utilities and outdoor space before budgeting two units.

Coming in 2027: SB 1117

SB 1117, Chapter 809, limits the applicable proportional impact-fee calculation to interior livable area above 750 square feet for properties with up to two ADUs. Properties with more than two have a different proportional rule. For an eligible 900-square-foot unit, the excess area is 150 square feet; this illustrates area only, not a fee or savings quote. Check local rates, unit count and assessment timing when effective.

Local application: San Francisco and San José

San Francisco’s State ADU process differs from ordinary home additions. San José preapproved plans still require site-specific documents and the current code cycle; modifications can trigger standard review. Preapproval is not a permit, and ZZA is not represented here as an approved city vendor. Consult each authority’s checklist and current fees; San José’s fee page lists a schedule effective August 11, 2026.

Turn the rules into a project checklist

Start with ZIP Code, use and existing dwelling type, then verify the jurisdiction with parcel information. Compare ADU, JADU and addition layouts. Separate design, permits, impact fees, school and utility charges, construction and finishes. Assign document responsibilities and retain written review milestones. Use this checklist in a ZZA consultation; agree deliverables and professional coordination before engagement.

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