Direct Answer: Yes. Starting January 1, 2027, AB 956 requires California cities and counties to ministerially approve two detached ADUs on a single-family lot. Building both can cost you your guaranteed junior ADU.
Most of the ADU questions I field start the same way. A homeowner wants one backyard unit for a parent, a renter, or an adult kid, and they want to know whether the city will actually let them build it.
Starting January 1, 2027, the answer gets bigger. AB 956, signed September 29, 2026, requires cities and counties to approve two detached ADUs on a lot with an existing or proposed single-family home, up from one.
Here is my take after watching how these projects actually go on Peninsula lots: the new law is real and useful, but it comes with a quiet trade-off. If you build both detached units, your local agency is no longer required to also approve a JADU on that lot. That decision needs to happen before anyone draws a single plan sheet.
What AB 956 actually changes on January 1, 2027
AB 956 was signed by Governor Newsom on September 29, 2026, as Chapter 791 of the Statutes of 2026. It takes effect January 1, 2027.
State law already required local agencies to ministerially approve one detached ADU on a lot with a proposed or existing single-family dwelling. The new law raises that to two.
What “ministerial” means in practice:
- No discretionary hearing and no design review board judgment call on whether your project fits the neighborhood
- The agency checks your plans against objective standards and issues the permit
- AB 956 also reduces the ability of local agencies to apply development standards to qualifying two-detached-ADU projects
Two other pieces matter. AB 956 widened HOA protections: HOAs and their CC&Rs can no longer prohibit or unreasonably restrict ADUs on any parcel zoned to allow single-family residential use. And a companion bill, SB 1117, signed the same day, limits impact fees.
One detail people miss: the two-unit rule covers detached, new construction. A garage conversion is a different permitting path under existing streamlined rules. You can read the state’s current ADU guidance through the California Department of Housing and Community Development.
The trade-off most homeowners do not see coming
Here is the part buried in the bill. If both detached ADUs are built on your lot, the local agency is no longer required to also approve a JADU there.
A JADU is a junior accessory dwelling unit, typically up to 500 square feet carved out of the existing house with its own entrance. On the Peninsula it is usually the least expensive unit you can create, because the walls, roof, and foundation already exist.
So the real question is not “can I build two.” It is which combination your lot can actually carry:
- Two detached units. Works on lots with genuine usable rear yard space. Think larger parcels in Carmel Valley, Prunedale, parts of Salinas, and some Pebble Beach lots.
- One detached unit plus a JADU. Often the better fit on tight lots in Pacific Grove, Carmel-by-the-Sea, and older Monterey neighborhoods where a second structure would eat the entire yard, parking, and side setbacks.
- One detached unit plus a garage conversion. Reasonable when the garage already has the footprint for a bedroom, bath, and kitchen.
I would rather have this conversation at the site visit than after plans are in review. Changing direction later means redrawing, re-engineering, and resubmitting. If you are still weighing the structure type itself, our breakdown on attached ADU or detached ADU walks through how lot shape drives that call.
Three paths for a single-family lot after January 1, 2027
This is how I frame the options when a homeowner asks what their lot can realistically support.
| Path | Best fit | Main trade-off |
|---|---|---|
| Two detached ADUs | Lots with real usable rear yard and room for separate utility runs | The agency is no longer required to also approve a JADU on that lot |
| One detached ADU plus a JADU | Tight Peninsula lots where a second structure would consume the yard | The JADU is small, usually capped around 500 sq ft, and shares the main house |
| One detached ADU plus a garage conversion | Properties with a garage large enough for a full unit | You lose covered parking and storage, which matters on narrow streets |
The order these decisions should happen in
Sequence matters more than speed on a two-unit project. This is the order I recommend.
What state law does not override on the Monterey Peninsula
Ministerial approval means the city cannot say no on taste. It does not mean every other requirement disappears.
The constraints I see slow Peninsula ADU projects down most often:
- Water. Plumbing-related work on the Peninsula runs through the Monterey Peninsula Water Management District, and new fixtures need water capacity. A permit from the city does not create water for your lot.
- Coastal zone review. Lots inside the coastal zone have their own layer. We covered the recent streamlining in building an ADU on coastal property.
- Septic and wells. In Carmel Valley and Prunedale, two additional units can push an existing septic system past its design capacity.
- Electrical service. Older Monterey and Pacific Grove homes often sit on panels that cannot carry two more kitchens, two more water heaters, and EV charging.
- Tree and forest rules. Pebble Beach lots carry Del Monte Forest requirements on top of everything else. See what Del Monte Forest rules add.
Requirements vary by jurisdiction, and Carmel-by-the-Sea, Pacific Grove, and unincorporated Monterey County each handle this differently. Verify with the building department that covers your address before you commit to a layout.
What two units cost compared to one
I get asked for a number early, and I understand why. One homeowner who reached out recently just wanted to know the most workable way to get a detached two-bedroom, two-bath unit built.
I will not throw a figure at you without seeing the site. Costs in Monterey County vary widely, and the things that move the number most are:
- Distance from the main house to each unit, which drives trenching for water, sewer, gas, and electrical
- Site conditions, including slope, soil, and whether equipment can even reach the back of the lot
- Whether your existing electrical service and sewer or septic can absorb the load, or need upgrading first
- Finish level, foundation type, and whether you use county pre-approved plans or custom drawings
One thing I can say with confidence: building both detached units in a single project almost always costs less per unit than building one now and another in four years. You pay for mobilization, excavation, inspections, and utility work once instead of twice.
We use realistic allowances in our proposals with every line item explained from day one, not a low number that grows later. If taxes are part of your math, read how an ADU changes your property tax bill.
Frequently Asked Questions About Building Two ADUs in California
Can I build two ADUs on my property in California in 2027?
Yes, if your lot has an existing or proposed single-family home. Starting January 1, 2027, AB 956 requires local agencies to ministerially approve two detached, new-construction ADUs on that lot. Whether your specific parcel can physically fit both is a separate question from whether the law allows it.
Do I lose my junior ADU if I build both detached units?
Under AB 956, if both detached ADUs are built, the local agency is no longer required to also approve a JADU on that lot. That is why I push homeowners to settle the layout before plans get drawn.
Can my HOA block an ADU?
AB 956 widened the protections. HOAs and their CC&Rs can no longer prohibit or unreasonably restrict ADUs on any parcel zoned to allow single-family residential use. The earlier version of state law used narrower wording, so homeowners who were told no in the past may want to recheck.
Should I wait until January to submit my plans?
If you want two detached units, yes, the expanded approval requirement starts January 1, 2027. But do not sit idle until then. Site evaluation, water capacity checks, and permit-ready drawings routinely take weeks to a few months, so that work can happen now.
Does a garage conversion count as one of the two?
The two-unit requirement in AB 956 applies to detached, new construction. Garage conversions run through the separate streamlined path California already created for converting existing structures. Confirm how your local building department treats the combination before you plan around it.
Thinking through what your lot can hold before 2027?
The homeowners who get the best outcome from this law change are the ones who settle the two detached versus one plus JADU question early, with real site measurements in hand. Our team handles well-planned, professionally managed projects across Monterey, Pacific Grove, Carmel, Pebble Beach, Salinas, and the rest of Monterey County, including the pre-construction planning that gets ADU plans permit-ready. If you want to talk through your property, we are reachable at (831) 220-3334 or at palaciosconstructionca.com.
