California lawmakers just sent AB 956 to the Governor. If signed, a single-family lot could hold two detached ADUs. Here's what San Diego owners should know.
On August 27, the Assembly agreed to the Senate's changes to AB 956 and sent the bill to be enrolled — the last procedural step before it lands on the Governor's desk. It is a short bill with a big idea behind it: on a single-family lot, you could build two detached ADUs instead of one.
It is not law yet. The Governor still has to sign it, and because it carries no urgency clause, it would take effect January 1, 2027 if he does. But if you are sketching out a project this fall, this is worth understanding now, because it changes what "the most I can build here" means for a lot of San Diego County properties.
What AB 956 would actually change
Today, Government Code section 66323 gives homeowners a ministerial path — meaning the city approves it over the counter if it meets the standards, with no discretionary hearing — to build one detached, new-construction ADU on a lot with an existing or proposed single-family home. That unit gets four-foot side and rear setbacks, and the city may cap it at 800 square feet of livable space. Separately, you can add a junior ADU carved out of the existing house.
AB 956, authored by Assemblymember Sharon Quirk-Silva, rewrites that first line. Instead of one detached unit, the ministerial path would cover "two detached, new construction, accessory dwelling units" with the same four-foot side and rear setbacks.
Everything else in the section stays put. The four-foot setback allowance, the height rules, the 800-square-foot floor-area limit a city is allowed to impose — those still apply to each unit on this pathway. This is not a bill that makes ADUs bigger. It makes them more numerous.
The trade-off written into the bill
There is one important catch, and it is right in the text: a local agency is not required to ministerially approve a junior ADU on a lot where two detached ADUs have already been built.
So the choice becomes real. Two detached cottages in the yard, or one detached cottage plus a junior unit converted out of the existing house. Those are very different projects with very different costs, different construction sequences, and different rental profiles. A JADU shares walls and often utilities with the main house and is usually the cheapest square footage you will ever add. A second detached unit is a second foundation, a second roof, a second set of utility connections — and a second standalone rent.
That is exactly the kind of fork we walk through on a site visit before anyone draws anything. Our process starts with feasibility for this reason: the answer depends on your lot, not on the statute.
HOAs lose more room to say no
The second half of AB 956 is quieter but matters a great deal in North County. The bill amends Civil Code sections 714.3 and 4751 — the provisions that stop homeowners associations from banning ADUs outright — and broadens them in two ways.
The protection would apply to any lot "zoned to allow single-family residential use," rather than the narrower "zoned for" phrasing, and it would extend to all common interest developments rather than only planned developments. In plain terms: fewer HOAs would be able to argue they fall outside the rule.
Associations would still get to enforce reasonable architectural standards — siding, roof material, paint, screening. What they would have a harder time doing is imposing conditions that effectively prohibit a legal ADU. If you are in an HOA in Carlsbad, Encinitas, or anywhere in the county where CC&Rs have been the stated obstacle, this is the change to watch.
What it means for a real San Diego lot
A statute saying you may build two detached units is not the same as your parcel being able to hold two. Before the second unit is a plan, it is a set of physical questions:
- Room to place them. Two structures at four-foot setbacks still need separation from each other, from the main house, and from anything the fire code cares about. Long narrow lots often work better than wide shallow ones.
- Utilities. A second detached unit means a second set of connections. Sewer lateral capacity, main panel amperage, and water service sizing are the three things that most often quietly decide the budget.
- Grading and access. Getting equipment to the back half of a lot — and getting a second unit's drainage to work without re-engineering the yard — is real cost, not a footnote.
- Which pathway you use. The ministerial route in 66323 comes with the 800-square-foot ceiling a city may apply. Larger units go through a city's own ADU ordinance, with its own standards. Those are different applications with different timelines.
None of that changes on January 1. It just becomes worth asking on more properties than it was before.
What to do between now and January
If the second unit interests you, the useful moves right now are the boring ones. Get a current survey or a reliable site plan. Find out what your sewer lateral and electrical panel can actually carry. If you are in an HOA, read your CC&Rs so you know what architectural standards you would be designing to.
It is also worth looking at whether a pre-approved plan fits one or both units — a plan that has already cleared review is the shortest distance between a decision and a permit, and it makes the two-unit math much easier to pencil. On the money side, financing a two-unit project is a different conversation than financing one, and it is better to have it early. Our notes on ADU financing options are a reasonable starting point.
For the law itself, the California HCD ADU Handbook remains the best plain-language reference, and HCD updates it as new legislation takes effect.
If you want to know whether your lot could hold two detached units — or whether one unit plus a junior ADU is the smarter build — book a free site walk. We will look at the setbacks, the utilities, and the access with you, and tell you honestly what the property supports. As a construction management agency, our job is to give you that answer straight, before anyone spends money on drawings.
AB 956 is not signed yet. But it is close, and it is the kind of change that quietly doubles what a lot of ordinary San Diego backyards are allowed to become. Worth knowing where yours stands.