Accessory Dwelling Units (ADUs) are an important way to expand housing options within the community. This page provides helpful information and resources from the City’s Community Development Department — including the Planning and Building & Safety Divisions — as well as the Fire Department. Here, property owners, design professionals, and developers can learn about ADU development standards, permitting requirements, and safety regulations to create a compliant and safe ADU.

Development Standards

The City’s Municipal Code outlines specific development standards for ADUs to ensure they are designed and constructed in a manner consistent with local zoning requirements. Downey Municipal Code Section 9414 provides these standards, offering guidance on the regulations that apply when planning and designing an ADU. 

The City's Planning Division has prepared fact sheets to assist in further understanding ADU development standards for varying property types. Click on the property type below to understand what development standards will apply:

• Single-Family Residential 
• Multiple-Family Residential

Pre-Approved Standard Plans for Detached ADUs Program

To help streamline the design and permitting process, the city offers pre-approved standard plans for detached ADUs. These plans provide residents with cost-effective, code-compliant design options that can help reduce review times and simplify construction.

Learn more about the City's Pre-Approved ADU Plans Program here.

If you are a design professional that is interested in submitting your plans for consideration into the program, you may review the minimum submittal requirements here.

Submitting Plans for Review

ADU plans can be submitted via the City's online Accela Citizen Access (ACA) portal; all plans are required to be submitted electronically using the ACA portal. 

To use the ACA portal, you first register for a Citizen Access account, then prepare your digital plan-check package in the required format (including orientation, scale, and upload instructions). Once the files are ready, you must create an application within the ACA portal, upload your plans and supporting documents, and finalize the submission — you will be able to track your review status online. Building & Safety has created several helpful hand-outs and tutorial videos to further assist with the electronic plan submittal process; these resources can be found here.

When preparing to submit, please see the Building & Safety Division's Hand-outs/Forms webpage for submittal requirement checklists.  

Fire Plan Guide

Additionally, the City's Fire Department has prepared a comprehensive ADU Fire Plan Guide to assist in understanding the fire- and life-safety requirements associated with constructing an ADU. The guide covers critical topics such as fire department access, fire sprinkler and hydrant requirements, egress and emergency escape, smoke alarms and detection systems, and other key elements necessary to comply with both local and state fire safety standards.

ADU Updates Newsletter

The Community Development Department has created an ADU Newsletter that summarizes the latest changes in state and local ADU regulations, along with current trends. The City remains committed to keeping the community informed, and supporting property owners, design professionals, and developers through the ADU development process.