Accessory Dwelling Units and Guest Houses

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Rendering of a Studio Option with Mid Mod Architecture

What is an Accessory Dwelling Unit?

An Accessory Dwelling Unit (ADU) is another home on your property. It can take many forms - a separate small home, an apartment over a garage, or in a basement. It can be created by remodeling your existing home and garage or making additions to it. An ADU will always contain everything someone needs to live, including a kitchen, bathroom, and place to sleep.

Utility cost may change due the installation of an ADU. For more information, please see: Cost of an ADU

Since the last update to the City’s ADU requirements in 2021, certain City zoning regulations in Chapter 40 may be different due to State updates to ADU laws. Please refer to Government Code Section 6585.2 for the most updated information. The City will update the code on a rolling basis for consistency and clarity.

What is a Guest House?

A Guest House is living quarters or conditioned space within an accessory building for the use of persons living or employed on the premises, or for temporary use by guests of the occupants of the premises. Such quarters may have bathroom facilities (toilet, sink, tub/shower) and shall have no kitchen facilities. Such quarters shall not be rented or otherwise be used as a separate dwelling. A pool house, workshop, home office or studio is also considered a guest house.

Outside Pre-Designed ADU Options?

Are you an ADU designer? Now your designs can be plan-checked by the City (at your cost) and once accepted by the City as a “master plan,” can be posted on the City’s ADU webpage as a resource for property owners exploring building an ADU. The available plans would be for reference only and incomplete—not construction level drawings that can be submitted for a building permit. Property owners shopping for plans will only have access to view the elevations and floor plans. The review time will be reduced for you and your client since the plans will have already been plan checked and reviewed by the City prior to issuance of a building permit. Site plan review by Planning for individual projects will also still be required prior to submitting for a building permit.

AB 1332, a new State law provides greater access to less expensive design options for building an ADU went into effect January 1, 2025. Once the City has plans accepted as a “master plan” they will be made available on the website. If you are thinking about an ADU and exploring how to keep costs as low as possible, check back from time to time to see if any plans have become available.

Types of ADUs

Type 1 (Building Permit Only)

If a project is able to meet the requirements of those specified on page 2 of the Accessory Dwelling Units and Guest Houses Guidelines, it does not require a permit from the Planning Division. Zoning tools such as lot coverage, open space requirements and floor area ratios are not applied to Type 1 ADUs.

Type 2 (Junior Accessory Dwelling Unit)

Type 2 ADUs have the same approval process as Type 1 ADUs. A Junior Accessory Dwelling Unit (JADU) must be within the walls of the habitable portion of the single family residence, not including the garage or carport. Standards are found on page 3 of the Guidelines.

Type 3 (Ministerial Permit)

ADUs are eligible for a Ministerial Permit if they do not meet the requirements for a Building Permit Only but meet the requirements listed on pages 4-5 of the Guidelines. Lot coverage, floor area ratio, and open space requirements apply to a Ministerial ADU.

Type 4 (Non-Ministerial)

Type 4 ADUs do not meet the requirements for a Ministerial ADU or Building Permit Only. Non-Ministerial ADUs are subject to the regulations on pages 6-7 of the Guidelines and require the approval of an administrative use permit that is administered by the Planning Department.

Pre-Designed ADU Plans

The City of Davis offers free sets of pre-designed plans. The size options include a 300 SF studio, a 565 SF one-bedroom, and a 740 SF two-bedroom design. In order for a building permit to be issued, the pre-designed plans shall be submitted for the Community Development Department and are subject to the typical review process. However, the pre-designed plans have already been reviewed for compliance so the process is shortened and cheaper.

More information on the Pre-Designed ADUs visit the Pre-Designed ADU Webpage.

Additional Information and Links

Accessory Dwelling Unit and Guest House Guidelines and Application Package
Accessory Dwelling Unit and Guest House Application Form
(for Ministerial Type 3 ADUs, Non-Ministerial Type 4 ADUs, and Guest Houses)

On May 18, 2021, the Davis City Council adopted Ordinance 2602, which amended the Davis Municipal Code pertaining to Accessory Dwelling Units. The primary purpose of the update was to bring the City's ordinance into compliance with the regulations of the State of California. Now, there are several different ways anyone can receive approval for an ADU on their property. Staff has prepared the information packet explaining the requirements for each type of ADU. Just click on the links below to view a copy of the information and application form.

City of Davis Ordinance 2606