California ADU setback tracker: side and rear lot lines
Check HCD’s guidance for California ADU side and rear setbacks, existing-structure exceptions, and the dates behind this rule review.
The rule described in the reviewed guidance
HCD’s March 2026 handbook says an attached or detached ADU may be subject to side and rear lot-line setbacks of no more than four feet under Government Code §66314(d)(7). That is a limit on the setback an agency may require, not a universal requirement to build exactly four feet away.
HCD also describes an exception for conversion within existing space or replacement in the same location with the same dimensions. Do not apply that exception automatically to an enlarged or moved structure. Coastal requirements and building/fire rules need separate review.
Rule and source status register
Status applies to this reviewed source edition. A draft, proposal or press announcement is not an effective requirement.
HCD handbook, legislative changes, p. 46 ↗HCD handbook publication page ↗
| Item | Status in this pilot | Date and evidence | Practical implication |
|---|---|---|---|
| Side/rear setback limit and existing-structure exception | Effective rule as described by HCD | March 2026 handbook, p. 37; checked October 15, 2026. Original enactment date not established in this pilot. | Review §66314(d)(7) and the actual project configuration. |
| SB 543 size terminology affecting the 800-square-foot safeguard | Enacted / effective | January 1, 2026, per HCD handbook p. 46; §66321(b)(3) uses interior livable space. | Keep size measurement separate from the four-foot setback limit; this did not establish a new four-foot rule. |
| March 2026 handbook | Published agency guidance | March 2026; retrieved October 15, 2026. | Guidance publication is not a legislative adoption or effective date. |
| Proposed or adopted-but-not-effective changes | No entry verified for this limited register | No comprehensive pending-bill survey performed. | Do not interpret this as proof that no legislation is pending. |
A useful site-review worksheet
For a proposed detached ADU, record whether it is entirely new, a conversion, or a same-location/same-dimensions replacement. Identify the actual side and rear property lines on a surveyed site plan. A fence does not establish the lot line.
Ask the permitting agency which statutory pathway it is reviewing and which building, fire, easement or coastal constraints apply. Front setbacks and distances between buildings are separate questions. This pilot covers side and rear lot-line setbacks; it does not compute a buildable envelope.
- Parcel and permitting authority: ______
- Proposed work and existing structure dimensions: ______
- Side and rear measurements and source plan: ______
- Applicable section and agency response, with date: ______
- Coastal/building/fire/easement questions unresolved: ______
How this helps a supplier
Use a documented rule question to understand the project stage before discussing products. A rule allowing an ADU does not mean a permit was issued, construction started, or a contractor needs bids. Record those as separate evidence questions.
Source limits and next check
This edition relies on the state housing agency’s official handbook. Direct retrieval of the Legislature’s code pages returned HTTP 403 during review; the statutory citations above were verified in HCD’s guidance, not independently against the live code. Confirm current law and local application with the permitting authority before designing or filing.
Review HCD’s handbook and linked statutory text quarterly, next by January 15, 2027, and after a relevant adopted change. Keep proposal, adoption, effective date, and guidance publication separate. If a newer law cannot be verified, preserve the dated guidance and mark the changed requirement unresolved. Change log: initial register, October 15, 2026.
HCD ADU guidance and update notices ↗Official Government Code §66314 (access failed during this check) ↗
Your checklist
0 of 5 reviewed. Progress stays in this tab; download the worksheet to keep notes.
Sources and method
Sources reviewed October 15, 2026 unless a record carries its own observation date.
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