A project of the Santa Clara County Planning Collaborative

A project of the Santa Clara County Planning Collaborative

2 Learning the Rules

BEFORE YOU BEGIN DESIGNING YOUR ADU you need to know what you’re allowed to build. We will help you navigate the state and local laws that apply to your property.

Looking for your local rules? go here


Here are a few of the most frequently asked questions about ADU rules. See the content below and our ADU Guidebook for more guidance, resources, and tips for all steps of the process. 

Make sure to look at your local ADU rules to understand what applies in your location. 

In almost all cases, yes! ADUs and JADUs are allowed in all single-family and mixed-use zones. If residential buildings are allowed, ADUs are almost always allowed too (with limited exceptions for safety, traffic, and water).

Homeowners can convert legally built structures (garage, barn, art studio, etc.) into an ADU. JADUs can be converted from an attached garage (but not detached). If you demolish your garage or other enclosed structure and build an ADU in its place, the ADU can be in the same footprint if it’s the same size and height of the structure it’s replacing. You may need to provide replacement parking; check Local ADU Rules or more details.

If you plan on replacing a detached garage with an ADU, demolition permits, and public notice cannot be required if you have your ADU permit (unless it is in an architecturally and historically significant district). Check with staff for other garage-related policies.

Note that garage conversion ADUs may require significant moisture barriers and other design elements in order to meet building codes.

ADUs and JADUs are allowed in all residential and mixed-use zones, with limited exceptions for safety, traffic, and water.

According to state law, you can build up to an 800 square foot ADU, as long as it is not over 16 feet tall and rear and side setbacks are 4 feet or more. Otherwise, size limits depend on your property and local rules. No room behind or next to your main home? You can build it in your front yard instead.

According to state law, rules about setbacks, lot coverage, and open space requirements cannot restrict you from building an 800 square foot ADU, as long as the ADU has setbacks of at least 4 feet and is not above 16 feet tall. Front setbacks also cannot restrict you from building an 800 square foot ADU, which means an ADU can be in a front yard – but only if rear or side placement isn’t possible.

JADU owners need to live in the primary unit or the JADU – and this may need to be recorded in a deed restriction for the property. You may also be required to live on the property if it includes an ADU. Check Local ADU Rules and talk with staff early to find out. 

Generally, ADUs and JADUs cannot be rented for fewer than 30 days at a time.

Parking is much less of a concern than it used to be. JADUs do not require a parking spot. Check Local ADU Rules and talk with your staff to see if ADUs require parking. No new parking is required if ADU is:

  1. Within ½ mile walking distance to transit (including a ferry);
  2. Within an architecturally or historically significant district;
  3. On-street parking permits are required and not provided to the occupant of the ADU;
  4. Located within one block of car-share access, or
  5. Built as part of a new home.

Check the Local ADU Rules to see what parking may be required. 

\Homeowners can build both an ADU, and JADU on their property. Some cities allow you to build more. Multifamily properties can have multiple ADUs, depending on the type and other details of the project.Contact staff for more information if interested in building ADUs on a multifamily property.


Learning the Rules


Learn about your property

First, you’ll gather some basic information about your property – what’s your Assessor’s Parcel Number (APN)? How big is your lot size and how is it zoned? Use the County Assessor’s Property Search Tool to find your Assessor’s Parcel Number (APN) and our Exercises to record some basic information on your property. Our Guidebook describes this step in more detail.

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Learn what you can build

Next, you’ll need to understand what’s possible to build on your property. There are local and state laws that control the size, position, height, and other qualities of your ADU, as well as rules about parking, fire safety, and more. See your local ADU Rules for a comprehensive overview of your City’s ADU rules, plus our Guidebook for more detailed information about important ADU laws.

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Meet with city staff

One of the best things you can do is to talk to City staff early in the process about potential issues and other standards that might apply. Most cities have a Planning or Permit Counter where you can ask questions without an appointment, or you can call or email. Depending on the city, you may be able to schedule an appointment. For contact information, see Local ADU Rules and Contacts.

If you decide to move forward, it’s a good idea to return with your final design for input before submitting your planning application. Staff will alert you to anything you should address before you submit.

Use our Exercises to help plan your conversation and take notes on the planner’s responses.This is also a good time to contact your utility service providers (waste, sewer, gas, electricity, etc.) to confirm requirements, timelines, and fees. Contact information is in the Local ADU Rules and Contacts and in the directory at the end of our Guidebook.

Confirm with City staff if your property falls within any special zones that may impact what you can build. These may include Historic Districts, Coastal Zone, Utility Districts (Water, Sewer, Gas & Electric), Fire Hazard or Other Hazard Zone, etc. Ask staff about other local requirements or rules that may affect your project.

If your basic project details (size, number of bedrooms) change based on this meeting, it’s a good idea to adjust your estimated project budget.

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