Two ADUs on one lot? What Sacramento decides before August 31

An owner in Sunnyvale asked me a couple weeks ago whether she should start drawings on a second backyard unit. Six thousand square foot lot, one detached ADU already built in 2023, plenty of room left. I told her to give it three weeks.

That's not the kind of advice anyone wants, so let me explain what I was waiting on.

The two bills in play

Every bill in the California Legislature has to clear both houses by midnight on August 31. Two of them would change what you're allowed to put in your backyard and what it costs you.

Neither one is a rewrite of ADU law. Compared to the batch that took effect this January, these are narrow, technical fixes, the kind that don't make the news and then quietly change your project budget by five figures.

AB 956: two detached ADUs, and HOAs lose a veto

Start with the count, because that's the part people care about. Today, state law generally gets you one ADU plus a junior ADU carved out of the existing house. Two freestanding structures in the backyard isn't on the menu. Sharon Quirk-Silva's bill puts it there by raising the detached limit from one to two.

It also bars homeowners associations from blocking an ADU that complies with state law. If you've followed the HOA litigation on this, you know courts have been sorting it out case by case. A statute settles that faster than a published opinion does.

Buried further down is a zoning wrinkle that trips up more Bay Area owners than you'd think. Plenty of single-family houses sit on land zoned for multi-family. The existing statute talks about lots "zoned for single family use," and some cities have read that narrowly to deny ADUs on those parcels. AB 956 says the rights apply anyway. If that sounds like an edge case, it isn't in older parts of San Jose and Santa Clara, where the zoning maps and the houses stopped agreeing decades ago.

Where it stands: the Senate read it a second time on August 13 and ordered it to third reading, after amending it on the 12th. It also skipped Appropriations, which is generally a sign a bill isn't in trouble.

SB 1117: impact fees on the part above 750 square feet

This one is drier and probably worth more money to you.

ADUs of 750 square feet or less are already exempt from impact fees. Go above 750 and cities can charge you, proportioned against the primary dwelling. Cervantes' bill changes the math so the charge applies only to the area in excess of 750 square feet.

Run that on a real project. Build a 1,000 square foot two-bedroom and your fee base drops from 1,000 square feet to 250. Same unit, same permit, roughly a quarter of the fee exposure. On a 1,200 square foot unit it's better still.

I've watched owners shave a perfectly good floor plan down to 749 square feet purely to duck a fee cliff, and end up with a unit that rents for less every month for the next thirty years. That's a bad trade made for a rational reason. SB 1117 mostly removes the reason.

It passed the Senate 37-0 back in May, went through the Assembly, and as of August 20 it's sitting in the Senate waiting on concurrence in the Assembly's amendments. Nobody voted against it.

Passing isn't the same as being law

This is where people get ahead of themselves.

August 31 is the passage deadline, not the finish line. The governor then has until September 30 to sign or veto. Bills enacted on or before October 2 take effect January 1, 2027.

So even if both bills sail through and get signed, nothing changes for a permit you pull this fall. The earliest either one helps you is a January application, which is worth knowing before you tell your contractor to sit tight for something that was always four months out.

Should you wait?

Depends which bill you're waiting on, and I'd answer these differently.

If it's SB 1117, waiting has an actual dollar figure attached, and the bill's had a clean run. But check your own city's fee schedule before you decide anything. Impact fees vary enormously across the Bay Area, and in a few jurisdictions the number is small enough that the whole question is academic. Some cities also waive or defer ADU fees on their own. Pull the schedule, find your number, then decide whether it's worth three months.

If it's AB 956, I'd design for it rather than wait on it. Tell your architect you want a site plan that works with one detached unit and can take a second later. That costs you very little now and saves a redesign if the bill lands. If it dies, you build the one unit you were always going to build. Permit timelines being what they are, the review queue itself will eat more of your calendar than this bill will.

And if you're not building at all, if you already own an ADU and you're wondering whether this changes your rental income, the near-term answer is no. Longer term, more legal backyard units across Santa Clara and San Mateo counties means more competition, though we're talking 2028 and beyond before it's visible in what you can charge. I wouldn't reprice anything over it.

What I'd do in the next ten days

Pull your city's ADU impact fee schedule and find the actual number for the size you want. Most Bay Area cities post it. If you can't find it, the planning counter will tell you over the phone.

If you're in an HOA, read the CC&Rs now and note anything about accessory structures, setbacks, or architectural review. If AB 956 passes, a lot of that language stops being enforceable against a compliant ADU, and you'll want to know exactly which clauses you're about to stop worrying about.

If your house sits on a multi-family-zoned parcel and a city planner has ever told you that's a problem, write down who said it and when. That's precisely the situation AB 956 addresses.

Then watch the last week of August. Bills die quietly at that deadline all the time, and the ones that pass usually pass in the final few days.

None of this changes how you'd run the unit once it's built. What it changes is how big it can be and what the city gets to charge you on the way in. On a quarter-acre lot in Sunnyvale, those two numbers are most of whether the project pencils.

Thinking about a second unit, or want to know what your existing ADU should be renting for? Get a free ADU rental analysis and I'll go through the numbers for your specific property. Or call me at (408) 813-8001.

Sources

• AB 956 bill status, California Legislative Information — California State Legislature
• AB 956: Double Detached ADUs — California YIMBY
• SB 1117: Accessory dwelling units and junior accessory dwelling units — CalMatters Digital Democracy
• SB 1117 bill text — California State Legislature
• 2026 Tentative Legislative Calendar — California State Senate
• 2026 Legislation tracker — California YIMBY