Accessory Dwelling Unit (ADU)

An Accessory Dwelling Unit (ADU) is a building which provides independent living facilities for one or more persons on the same parcel on which one or more dwelling units are located. An accessory dwelling unit (ADU) shall include independent living, sleeping, eating, cooking, and bathing facilities and may be detached from, within, or attached to a dwelling unit. Developing an ADU may involve new construction (pre-fab or stick built) or the conversion of existing building space.

A Junior Accessory Dwelling Unit (JADU) is an accessory dwelling (ADU) that is no more than five hundred square feet in size and contained entirely within an existing dwelling unit, which includes cooking facilities that provides equal to or greater accommodations as an efficiency kitchen and may include independent bathroom and bathing facilities, or may share bathroom facilities with a dwelling unit.

To sign up to receive updates on ADU information in unincorporated Stanislaus County please email with subject line “ADU Subscribe”.

  • ADUs are an affordable type of home to construct in California because they do not require paying for land, major new infrastructure, structured parking, or elevators.
  • ADUs can provide a source of income for homeowners.
  • ADUs allow extended families to be near one another while maintaining privacy.
  • ADUs can provide as much living space as many newly-built apartments and condominiums, and they’re suited well for couples, small families, friends, young people, and seniors.
  • ADUs give homeowners the flexibility to share independent living areas with family members and others, allowing seniors to age in place as they require more care.

Stanislaus County allows ADUs in the following zoning districts throughout unincorporated Stanislaus County:

  • Residential zoning districts
    • R-1 (low density residential)
    • R-2 (medium-density residential)
    • R-3 (high-density residential)
    • R-A (rural residential)
    • Planned development (P-D) zoning districts permitting residential uses
  • A-2 (general agriculture) zoning districts.

The County Planning and Community Development Department's Interactive Permit Guide can be used to determine whether a parcel located in the unincorporated County area can develop an ADU. By entering your address or Assessor's Parcel Number, the permit guide will provide information on whether an ADU is permitted and the steps that will need to be taken in order to obtain a permit for the ADU.

Interactive Permit Guide

Check Your Zoning

Chapter 21.74 Accessory Dwelling Units (

Stanislaus County in partnership with the cities of Ceres, Modesto, Oakdale, Riverbank, Turlock, and Waterford have developed seven (7) different ADU plans for detached new construction, each with multiple options for exterior finishes, available free to property owners.

ADU Plans are available free of charge to property owners within unincorporated Stanislaus County, Ceres, Modesto, Oakdale, Riverbank, Turlock, and Waterford. See available ADU floor plans and elevations below. All plan sets have been plan checked and approved by the Stanislaus County Building Division.

For more information on the pre-plan checked ADU Plans please email

In order to build an ADU you must first obtain a building permit. Only a property owner or licensed contractor (not a tenant or lessee) may be issued a building permit. Building Permit Applications can either be submitted online or over the counter at 1010 10th Street Suite 3400. Services are offered by phone, email, online, and in person. Appointments for all in person assistance are strongly encouraged. For office hours and information on scheduling an appointment please contact us.

For the Online Building Permit Application access: Accela Citizen Access

For a fillable Building Permit Application to be submitted in the office, you can download here.

You will need to submit the following documents with your Building Permit Application:

  • Plot Plan Drawn to Scale - Show Complete Parcel with all Dimensions; Location of Proposed Work; Driveway Location and Width; Easements; The Direction North; Well Location; Existing and proposed Septic System; All Setbacks from: Property Lines, Existing Structures, Pools, Septic System, Water Supply (existing and proposed), Etc. (3 Sets)
  • Fire Sprinkler Plans - If the main dwelling is fire sprinklered (can be submitted as a deferred submittal)
  • Floor Plan (not required with pre-plan checked ADU Plans) - show existing and Proposed area, label use of all rooms (3 Sets)
  • Foundation Plan and Related Details (not required with pre-plan checked ADU Plans) (2 sets)
  • Floor Framing Plan with Details (not required with pre-plan checked ADU Plans) (2 sets)
  • Roof Framing and Related Details (not required with pre-plan checked ADU Plans) (2 sets)
  • Engineered truss calculations and layout (if applicable) (2 sets)
  • Construction Details (not required with pre-plan checked ADU Plans) (2 sets)
  • Elevations - Front, Both Sides and Back (not required with pre-plan checked ADU Plans) (3 sets)
  • Engineering Calculations (not required with pre-plan checked ADU Plans) - Stamped and Wet Signed (2 sets)
  • Electrical Plan with Legend (not required with pre-plan checked ADU Plans) (2 sets)
    • Photovoltaic system plans (if applicable) - Required for all new construction detached ADUs.
  • Plumbing Plan with Legend (not required with pre-plan checked ADU Plans) (2 sets)
  • Heating and Air Conditioning Plan and Title 24 Energy Calculations (not required with pre-plan checked ADU Plans) (2 sets)
  • Grant Deed - Recorded copy that shows the property legal description
  • Assessor Records - Complete copies. These may be obtained from Stanislaus County Assessor’s Office 525-6461
  • Other documents as determined to be required based on project type and location

San Joaquin Valley Regional Planning Agencies Policy Council:

The San Joaquin Valley REAP program has developed a template ADU program for cities across the San Joaquin valley to use, for free. The website provides an Informational ADU Handout for the General Public, an ADU Implementation Guide for Local Planners, a Slide Deck Template local planners can use at their planning commission and city council meetings, an overview of existing ADU ordinances and Programs, a sample HCD approved Ordinance you can use in your jurisdiction, and free ADU Housing Plans…a complete suite for implementing an ADU Program in your community!

California Housing and Community Development Department (HCD):

The California Department of Housing and Community Development (HCD) conducts research and analysis of California's housing markets, identifies California's housing challenges, and develops policies that support housing and community development. This website provides an overview of ADU funding programs, current laws, HCD’s ADU Handbook and other ADU resources and information.

CalHFA ADU Grant Program:

CalHFA offers an ADU Grant to homeowners which provides up to $40,000 towards pre-development and non-reoccurring closing costs associated with the construction of the ADU. Predevelopment costs include site prep, architectural designs, permits, soil tests, impact fees, property survey, and energy reports.

Stanislaus Equity Partners (STEP):

STEP offers homeowners a variety of tools ranging from information to financing, design, permitting, and construction services to build new Accessory Dwelling Unit (ADUs) in approved areas of Stanislaus County.