ADUs in Santa Clara County: How the Permitting Really Works in 2026

ADU can add value, space, and flexibility!

People usually come to the idea of an accessory dwelling unit standing in their own backyard, looking at a detached garage or a stretch of grass, doing math in their head. The picture is clear: a second small home back there, a place to rent out or to use. The path from that picture to a finished, permitted unit is where most of the confusion lives, and where a lot of people stall for a year before they start. The rules changed again for 2026, mostly in the direction of making this easier, so it's worth understanding the terrain before you talk to a contractor.

If you're weighing whether an ADU makes sense on your property, here's how the permitting works, what shifted this year, and where the real answers for your specific lot live.

What an ADU is, and what changed for 2026

An ADU is a self-contained second dwelling on a lot zoned for a home: its own kitchen, bath, and entrance. A junior ADU, or JADU, is a smaller unit carved out of the existing house. California has spent several years steadily loosening the rules, and a fresh batch took effect this year. As Holland & Knight summarizes in its review of the 2026 housing laws, AB 1154 relaxed owner-occupancy conditions on certain JADUs, AB 462 streamlined ADU approvals in the coastal zone, and SB 9 (2025) pushed local ordinances to line up with state law. The direction of travel is fewer local obstacles, faster approvals.

The state sets the floor, your city writes the details

Here's the structure that trips people up. California's Department of Housing and Community Development sets statewide baselines for ADUs, things like size allowances, reduced setbacks, limits on parking requirements, and a ministerial approval process that removes much of the discretion cities used to have. Your city or county then implements those baselines through its own ordinance and its own counter. So the state law tells you what a city cannot forbid, and the local ordinance tells you the forms, fees, and timeline you'll navigate. Both are true at once, which is why one neighbor's experience two towns over may not match yours.

The permit path for ADUs in Santa Clara county

Stripped down, the sequence looks like this.

1. You confirm what your lot allows under both state law and your local ordinance.

2. You have plans drawn that meet code.

3. You submit for a building permit, and for a compliant ADU the review is meant to be ministerial, approved or denied against clear standards rather than sent to a discretionary hearing. State law sets deadlines on how long that review can take.

4. You build, you pass inspections, you get a certificate of occupancy.

   
   

The friction is rarely the concept. It's utilities, setbacks, fire access, and the specific fee schedule of your jurisdiction, the details that decide whether your plan pencils out.

The specifics for your lot belong to your city and the county

I'm going to be straight with you about the limits of a blog post. ADU rules carry real numbers, size caps, setback distances, fee amounts, parking triggers, and those numbers vary by jurisdiction and get amended almost every year. I won't quote a figure here and have you build a plan on a rule that changed last month. For your parcel, the authoritative sources are HCD's ADU pages for the state baseline and your city or Santa Clara County planning counter for the local ordinance and current fees. When a question touches what's legally allowed on a specific property, I bring it to my brokerage and the right local official rather than guess, and I'd want you to do the same.

How I help you think about it

My role is not the drafting or the permit-pulling. What I do is help you think clearly about whether an ADU fits your goals for the property before you spend money finding out, and point you toward the right specialists: a designer who knows the local counter, a contractor who has finished ADUs in Santa Clara county, the planner who can confirm your setbacks. If you're buying with an ADU in mind, I can help you read a lot for its real potential and its real constraints, so the backyard vision meets the paperwork with your eyes open.

If you're turning an ADU over in your mind and want a clear-eyed sounding board before you commit, let's talk it through.

Book a discovery call.