ADU & Pre-Approved ADU Information

Accessory Dwelling Unit (ADUs) & Junior ADUs

Accessory Dwelling Unit (ADU) - often referred to as granny flats, in-law suites, backyard cottages, or secondary units - are an increasingly popular way to add flexible housing options within existing neighborhoods. As California continues to address housing needs, ADUs have become an important party of the solution by offering additional, independent living spaces on residential properties.

An ADU is a self-contained residential unit that includes its own kitchen, bathroom, and living area, and is located on the same parcel as a primary residence. A Junior Accessory Dwelling Unit (JADU) is a slightly smaller unit, with a maximum size of 500 square-feet, created by converting part of an existing single-family dwelling, such as a spare bedroom or attached garage.

Together, ADUs and JADUs offer several benefits to Walnut residents:

  • Provide a cost-effective way to create new housing opportunities.
  • Offer supplemental income for property owners through rental potential.
  • Allow multigenerational living while preserving privacy and independence.
  • Deliver comfortable, efficient living spaces comparable to many new apartments and condominiums.
  • Enable aging in place, allowing seniors and families to remain close as car needs evolve.

Below you will find the City of Walnut’s current ADU Ordinance (No. 25-04) along with an informational handout outlining the various types of ADUs permitted, applicable development standards, and a submittal checklist to guide you through the application process.

For further details or questions regarding ADU regulations and requirements, please contact the Planning Division at (909) 595-7543.

Pre-Approved ADU Plans

Welcome to the Walnut Pre-Approved Accessory Dwelling Unit Program. Designed to streamline the permit approval process, this program offers homeowners and developers a selection of pre-approved ADU building plans that comply with the City’s Municipal Code, in accordance with Assembly Bill (AB) 1332. By utilizing Over-the-Counter (OTC) plan reviews, the program enhances efficiency and accessibility while supporting Walnut’s residential growth. 

To participate, Applicants must meet eligibility criteria and submit all required documents to the Planning Division. Be sure to review the appropriate checklist for your project to ensure a complete submission package. For detailed information on the OTC review process, submittal checklists, and pre-approved plan diagrams, explore the resources below. For additional questions, visit our FAQ page or contact the City of Walnut’s Community Development Department at (909) 595-7543. 

*NOTE: All Pre-Approved ADU Plans provided by the City have been developed by private contractors, selected through the San Gabriel Valley Council of Governments (SGVCOG). All plans are accessible for a fee, as set by the architect of record, and can be obtained by directly contacting the respective architect(s) listed.

Pre-Approved ADU Plans FAQ's
  1. Are the Pre-Approved ADU Plans Accessible for a fee?
    All Pre-Approved ADU Plans provided by the City of Walnut have been developed by private architects, selected through the San Gabriel Valley Council of Governments (SGVCOG). These plans are accessible for a fee, as set by the architect of record, and can be obtained by directly contacting the respective architect.

  2. Can the Pre-Approved ADU Plans be modified?
    Applicants may request alterations to the Pre-Approved ADU Plans. However, please note that any modified plans will no longer be eligible for pre-approval and will require a full standard plan check review.

  3. Can these plans be utilized to convert an existing structure (i.e., detached garage, pool house, guest house, into an ADU?
    No. The Pre-Approved ADU Plans provided are for the construction of new, detached structures only.

  4. How much does the City's Pre-Approved ADU Plan review cost?
    According to the City of Walnut's Development Services Fee Schedule(PDF, 873KB), the total cost for ADU plan review is $3,374.00. This includes the following:
    • Accessory Dwelling Unit (ADU) Review = $2,943.00
    • Environmental Exemption = $406.00
    • Document Imaging = $25.00
  5. What is the review process for the use of a Pre-Approved ADU Plan?
    There are two (2) review phases for the Pre-Approved ADU Plans: 1) Planning Review, and 2) Building and Safety Review. The Walnut Planning Division offers Over-The-Counter (OTC) Plan Review for those using the Pre-Approved ADU Plans. However, more complex projects may require a transition to a standard plan review.

    Once the Planning Review process is complete and a Project has been determined as approved, the Applicant(s) may submit their architectural and structural plans and a complete Building Permit Application to the Building and Safety Division for further review to ensure compliance with the California Building Code (CBC). Upon approval from both Divisions, all necessary construction permits will be issued.

  6. How does an Applicant indicate the use of a Pre-Approved ADU Plan on a Building Permit?
    When submitting your Building Permit Application, the Applicant(s) must indicate the name of the Pre-Approved ADU Plan within the 'Description of Work' and include 'Pre-Approved ADU Plan'.

  7. Why do 'Pre-Approved ADU Plans' still require Plan Check Review?
    Although the design and construction details of a Pre-Approved ADU Plan has been pre-reviewed by the Building and Safety Division, a Plan Review is still necessary to assess site-specific factors. This ensures that the chosen ADU design is suitable for your Property and meets all Code requirements.

    For instance, the proposed ADU may not be appropriate if it is located on a slope, beneath high-voltage power lines, fails to meet setback requirements, and/or exceeds the maximum lot coverage percentage. Additionally, existing conditions of the primary dwelling may trigger further requirements, such as fire sprinklers or solar panel installation.
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