Accessory Dwelling Units - ADUs

Accessory Dwelling Units:

What is an ADU?

An Accessory Dwelling Unit (ADU) is a self-contained living unit that is usually smaller than the main home on the same property. It contains a kitchen, bathroom, and a place to sleep. They can be attached to the main home or a separate detached building. They can also take the form of a Junior Accessory Dwelling Unit (JADU), which is a unit up to 500 square feet and are converted from any existing floor space (bottom illustration).

Example: Attached ADU

Attached ADU Diagram

Example: Detached ADU

Detached ADU Diagram

Example: Junior ADU

Junior ADU Diagram

ADUs have been an effective way of incorporating smaller living units into the fabric of the community that are affordable to a wider range of income levels, including elderly family members.   

Changes in State Law  

Due to the housing shortage in California, the State Legislature has passed significant housing-related laws in the past three years. In 2019, the legislature passed over 20 bills intended to fast-track housing production – including accessory dwelling units (ADUs). 

Updates to State Law expands areas and conditions under which ADUs can be built. The ADU Ordinance and ADU Handout both reflect the regulations permitted by new state law, effective January 1, 2023. Be advised that this information is subject to change, as state guidelines and interpretations are typically issued after the enactment of the new law. We have created an interactive map to help determine ADU parking requirements.

Obtaining a Permit

For ADU plans designed by a licensed professional or designer, please see Building’s Submittal Requirements for more information on what items need to be provided to obtain a permit.

Please Note:  The plans provided below do not reflect the current 2022 California Building Code. If you wish to use these plans, please contact the architect and engineer of record so they can revise the plans to reflect current building codes.  Any changes made will be at the applicant’s expense.

Free Permit-Ready ADU Plans:

Garden Cottage Program

On Monday, August 31, 2020, the Town of Danville launched its Permit-Ready Garden Cottage Program to incentivize the construction of quality ADUs that meet Danville's design and neighborhood compatibility standards. Danville Garden Cottage Flyer (PDF) 

The program offers a selection of pre-approved, permit-ready ADU building plans that can be downloaded free-of-charge (detached units only).  Because these ADU plans have been pre-plan checked, they are eligible for expedited processing and lower building permit fees.  

Applicants will need to consult with appropriate design professionals to prepare a plot/site plan and any necessary grading plans. Each project is unique and may require additional approvals and fees from other agencies. Table below is a simplified summary of what the Garden Cottage Program Covers. All other items will still need to be provided by the homeowner.

Garden Cottage Program
Steps to build an ADU with the Garden Cottage Program:Provided by the Garden Cottage Program Responsibility of the Homeowner

Finding and hiring a Designer/Architect to provide: 

  • plot plan
  • grading plan 
  • location of the ADU

Obtain Architectural Plans
Downloadable pre-designed plans
Choose and print/download appropriate plans
Obtain Structural Plans
Obtain Title 24 Energy Forms
Finding and hiring a Contractor to build the ADU & purchasing of materials
Submitting all required documents to apply for a permit Expedited Review over the Counter*
Payment of Permit FeesReduced Fees*
Payment of Plan Check FeesReduced Fees*
Obtaining Approval from Outside Agencies
Payment of Outside Agencies Fee(s)
Payment for and submitting Deferred Submittal for:
  • Solar Panels (PV System)
  • Utilities
  • Fire Sprinklers (if required)
Scheduling and Coordinating Inspections with outside agenciesNo

* If plans are modified application are subject to additional plan review and fees. If there are site specific conditions on your property, please consult a design professional to see if the Town's pre-designed plans can meet the parameters of your site conditions.

For more information, contact Civil Engineering Associate Guillermo Santolaya at (925) 314-3352 or