An Accessory Dwelling Unit (ADU) is a secondary housing unit on a single-family residential lot. ADUs are independent living spaces that come with their own kitchen, bathroom, and sleeping area. They offer a flexible housing solution to increase the supply of affordable housing without altering the character of established neighborhoods. ADUs can serve various purposes, including housing for family members, a rental for additional income, or as a home office.

What Are the Different Types of ADUs?

There are several types of ADUs, each catering to different needs and property layouts. Below are some descriptions of the types of ADU dwellings available and the requirements for construction.

Please note: If you’re converting an existing part of your home, converting an accessory structure, or adding an attached ADU to an existing part of the home or accessory structure, you probably won’t need to install solar panels. For the most part, new detached ADUs need to have solar panels to be in compliance with California Title 24 Building and Energy Efficiency Standards. (See details below under Detached ADU)

Title 24 exemptions to solar requirements:

• Manufactured units subject to Title 25 may not need to meet Title 24 requirements
• Attached ADUs are “additions”  Title 24 doesn’t require solar installation
• Conversion ADUs are “additions”  Title 24 doesn’t require solar installation
• Even detached conversions are “additions”  Title 24 doesn’t require solar installation
• There are conditions where you can be exempt because you don’t have a large enough surface area with unshaded solar access
  • “No solar is required if the effective annual solar access is restricted to less than 80 contiguous square feet by shading from existing permanent natural or man-made barriers external to the dwelling, including but not limited to trees, hills, and adjacent structures. The effective annual solar access shall be 70 percent or greater of the output of an unshaded PV array on an annual basis.“
• You can meet the solar requirements by adding panels to the primary house or elsewhere on the property
• You can meet the solar requirements by adding panels to an existing array

Will an ADU work on my property?

To determine if your property is suitable for an ADU, consider the following steps:

• Zoning Regulations: Check local zoning laws to ensure ADUs are permitted in your area.
• Lot Size: Review local codes for minimum lot size requirements for building an ADU.
• Setbacks and Coverage: Ensure there’s enough space on your property to meet setback requirements and that the ADU won’t exceed allowed lot coverage.
• Utilities and Access: Consider the accessibility of utilities and whether the ADU will have independent or shared access.