Accessory Dwelling Units

ADU Website Header

This Accessory Dwelling Unit (ADU) webpage is a one-stop-shop for information and resources to assist homeowners with building an ADU on their property. Two key features of this webpage include an ADU Manual and ADU prototype plans. The ADU Manual is essentially a how-to guide for ADUs. The City also prepared eight different permit-ready ADU prototype plans. Links to the ADU Manual and prototype plans, as well as additional information and resources, are provided below.

What is an ADU and JADU?

An Accessory Dwelling Unit, also known as an ADU, is a residential unit that is up to 1,200 square feet in size that provides independent living facilities that include a kitchen, sleeping, and bathroom facilities. An ADU may be incorporated into, attached to, or detached from a single-family, two-family, or multifamily residence and is subordinate to the principal residence. 

A Junior Accessory Dwelling Unit, also known as a JADU, is a residential unit that is no more than 500 square feet in size that is contained entirely within the walls of a single-family residence, including an attached garage, and that has a separate entrance. At a minimum, a JADU Unit includes an efficiency kitchen with a food preparation counter, cooking facility with appliances and storage cabinets, and may include a separate bathroom or may share a bathroom within the existing single-family residence. 

ADU Manual 

The City has prepared an ADU Manual, that is a how-to guide for ADUs. The Manual is designed for homeowners who are not familiar with the development process. Contents of the ADU Manual include: where to start, design considerations, ADU concepts and prototypes, implementation, glossary, and resources.

Prototype Plans 

RRM Design Group, an architectural consulting firm, prepared the City's ADU prototype plans. There are eight different plans, including five ADUs designed to be either attached or detached ADUs and three plans for converting a garage to an ADU. The prototype plans include studios, one-bedroom, and two-bedroom ADUs that range in size from 224 to 909 square feet. The ADUs are available in three different architectural styles: Spanish, Traditional, and Modern; however, the exterior colors, materials, and architectural style of attached ADUs will be required to match the primary residence.

ADU Prototype Renderings

With the prototype plans, the City will provide, free of charge, floor plans, elevations, electrical and plumbing plans, structural calculations, and preliminary energy calculations that have been reviewed for compliance with all required building codes to homeowners that are interested in building an ADU. The homeowner is responsible for completing the submittal requirements as outlined in the ADU Prototype Plans Checklist, including preparing a site plan and geotechnical report. The ADU prototype plans are designed with some ability for customization, such as selecting a window or door in a particular location. The prototype plans will save homeowners approximately $15,000 in architectural/design services, structural engineering services, and energy document preparation, as well as time.

To view the ADU prototype floor plans, elevations, and renderings, click on the links in the table below:

If you wish to apply for a building permit using one of the prototype plans, contact the Planning Division at and provide the property address and the ADU prototype plan number.  Staff will then email you the prototype plans for your use. 

In addition to the City’s prototype plans, homeowners can work with a design professional to design their own ADU, based on their needs. Many designers/builders offer standardized construction plans that can lower the costs of an ADU.

Building Permits

For information on applying for a building permit, please visit the City’s Building Permit webpage or contact the Building and Safety Division at (925) 833-6620.


Impact Fee Waivers

Per State law, effective January 1, 2020, through January 1, 2025, ADUs less than 750 square feet are not subject to impact fees and ADUs 750 square feet or larger are subject to impact fees proportional to the primary dwelling unit. For a complete list of City impact fees, please click here.

Permit Fee Waivers

To further incentivize ADUs, the City has waived permitting fees for building permits for ADUs applied for between January 1, 2022, and December 31, 2026. Permit fees are waived for ADUs less than 750 square feet and ADUs 750 square feet or larger that are deed restricted as lower-income units for a period of 55 years. This results in a savings of approximately $2,500 to $6,000 depending on the valuation of the ADU. When applying for a building permit, submit a completed ADU Permit / Plan Check Fee Waiver Form, if the ADU is eligible for a fee waiver.


AARP: The ABC’s of ADUsAccessory Dwelling Unit Regulations Brochure  
Alameda County ADU Resource Center
Backdoor Revolution: The Definitive Guide to ADU Development
California Department of Housing and Community Development: Second Unit Resources
California Department of Housing and Community Development: ADU Handbook
Dublin Accessory Dwelling Unit Manual
Dublin Municipal Code Chapter 8.80 (Accessory Dwelling Unit Regulations)
Step-by-Step Guide to ADU Design and Permitting
Video: 21 Elements: Bringing the Lessons Home (19:38)
Video: The Definitive Guide to ADU Development (22:20)
Video: The Definitive Guide to ADU Development Q&A (9:41)
Video: Policy Framework for Building Second Units (21:17)