In most of California, yes, you can build an ADU on a single-family or multifamily property, since state law requires cities to allow them on eligible lots. Setbacks, size limits, and local rules apply, but most single-family lots qualify. Here’s how to find out if you can build an ADU on your property.
Are you considering adding an ADU (Accessory Dwelling Unit) on your property but are unsure if it is even possible? In this full guide, we will cover all the aspects of building an ADU on your property. From understanding what exactly an ADU is, to knowing whether your property is suitable for it, and the zoning regulations for ADUs in Southern California, we have got you covered. Read on to learn everything you need to know about building an ADU on your property.
Here at GreatBuildz, a free service that connects homeowners in Los Angeles, Ventura, and Orange Counties with reliable ADU contractors, we speak to homeowners every day about planning for an ADU construction project – here are some considerations to get you started.
Understanding ADUs: What Are They?
ADUs (Accessory Dwelling Units) are self-contained living spaces that offer additional accommodation on residential properties. With their own kitchen, bathroom, and living areas, ADUs can be attached or detached from the primary residence and offer flexibility in design, as well as potential financial incentives.
They can be used to accommodate family members or generate extra income by being rented out. Local governments regulate ADUs and have specific requirements that need to be met for their construction and use. The popularity of ADUs has been growing in recent years due to the increased demand for affordable housing options, especially in urban areas where space is limited.
Is Your Property Suitable for an ADU?
Determining if your property is suitable for an ADU involves considering factors like lot size, zoning, and setbacks. Evaluate the space available on your property to see if an ADU can comfortably fit. Ensure there is access to utilities and consult with professionals for feasibility.
Related: https://www.greatbuildz.com/blog/los-angeles-50-most-common-adu-questions/
Zoning and Building Regulations
The state of California has implemented laws to promote ADU development and simplify the permit process. ADUs are permitted in most residential zones, including single-family and multifamily zones. However, local jurisdictions may have specific regulations regarding setbacks, lot size, and owner occupancy. It is important for homeowners to consult with their local department of building and safety before initiating an ADU project. By adhering to these zoning regulations, homeowners in Southern California can successfully handle the process of building an ADU on their property.
Setback Rules
Setbacks play a important role in ADU construction, determining the distance between the ADU and the property line or other structures. These setback rules are in place to ensure privacy, safety, and adequate space between buildings. ADUs may have different setback requirements compared to the primary dwelling.
The specific setback requirements can vary depending on the location and zoning regulations, but typically there is a minimum of 4 feet. Understanding and adhering to these setback rules is essential when building an ADU to comply with state laws and local ordinances.

How Big Can My ADU Be?
The maximum size of an ADU can be influenced by factors such as setbacks, height restrictions, and lot coverage. Localities may have minimum and maximum requirements for ADU size, with detached units typically allowed up to 1200 square feet.
The allowable size of an attached ADU can vary based on the square footage of the primary home – smaller homes may be allowed an attached ADU up to 800sf, and homes exceeding 2400sf may be allowed an attached ADU up to 1200sf. Homeowners should consult with local agencies to determine the specific square footage allowances for their ADU.
Height Restrictions for Building an ADU
When building an ADU, it’s important to be aware of the height restrictions that dictate the maximum height of the structure. The height limits can vary based on the zone and type of ADU, whether it’s attached or detached. Typically, the maximum allowable height for an ADU is 25 feet. To ensure compliance with these height restrictions, it’s advisable to hire a professional designer or architect who can help handle the regulations and create a plan that adheres to the guidelines.
Utility Installation for ADUs
Utility installation for ADUs involves connecting water, electricity, and sewer lines. Local building codes and utility providers have specific requirements for ADU utility installation. This may include the need for separate utility meters or shared meters with the main house. Proper utility installation is important for the safety and functionality of an ADU. To ensure compliance with utility installation requirements, homeowners should hire licensed professionals who are familiar with the local regulations and guidelines.
Title 24 Requirements for ADUs
Title 24 is a set of energy efficiency standards that covers various aspects of construction, including insulation, lighting, and HVAC systems. Title 24 also includes provisions for renewable energy sources and water conservation. By complying with these requirements, homeowners can reduce energy costs and minimize their environmental impact.
To ensure adherence to Title 24, it is advisable to consult with architects or contractors who are familiar with these standards. Their expertise will help guide the design process and ensure that the ADU meets all the necessary criteria.
Building ADUs on Multi-family Properties
Building ADUs on multi-family properties is a viable option for homeowners looking to maximize their property’s potential. These additional dwelling units can offer increased housing options and boost property value. However, Specific regulations must be followed when constructing ADUs on multi-family properties. Factors such as lot size and zoning can influence the number and size of ADUs allowed.
For example, multi-family properties can have up to two detached ADUs, each with a maximum size of 1200 square feet. Attached ADUs are also permitted, up to 25% of the total units of the main property (eg. an 8-unit apartment building may be allowed 2 attached ADUs). To navigate these regulations effectively, homeowners should consult with local agencies and professionals well-versed in ADU allowances for multi-family properties.

Interested in Building an ADU on Your Property?
Building an ADU on your property can be a great way to maximize space and increase your property value and real estate investment. However, it’s important to understand the zoning regulations and building restrictions in your area before proceeding with construction. Make sure to adhere to setback rules and height restrictions to ensure compliance with local regulations.
Familiarize yourself with the requirements for utility installation, as well as adhering to Title 24 standards. If you own a multi-family property, there may be additional regulations and allowances to consider when building ADUs. By ensuring you follow these appropriate guidelines, you can successfully build an ADU that meets your needs and enhances your property’s value.
Frequently Asked Questions
Can I build an ADU on my property in California?
In most cases, yes. California law requires cities to allow at least one ADU on eligible single-family and many multifamily lots, with streamlined approval. Setbacks, height, and size limits apply, and some overlays or lot conditions matter. Check with your city planning department to confirm what your specific lot allows.
What are the requirements to build an ADU?
Requirements include meeting size limits (up to 1,200 square feet for detached), setbacks (typically 4 feet from side and rear), height limits, and building code, plus a permit. California caps many local restrictions and requires 60-day approval. Your lot size, existing structures, and utilities also factor in.
How big of an ADU can I build?
California allows detached ADUs up to 1,200 square feet, and a junior ADU up to 500 square feet within the existing home. Local rules, lot size, and setbacks can affect the practical maximum. Attached ADUs may be limited to a percentage of the main home’s size. Check your city’s standards.
When it comes to planning and coordinating an ADU construction project, you shouldn’t have to go it alone – GreatBuildz is a free service that connects homeowners in Los Angeles, Ventura, and Orange Counties with reliable, thoroughly screened ADU contractors and provides project support from start to finish.