ADU setback requirements in California are generally 4 feet from the side and rear property lines, with no additional front setback required beyond what your zoning already allows. Converting an existing garage or structure can often be done with no new setback at all. Here’s how ADU setbacks work and what they mean for where you can build.
ADU laws and regulations in California can sometimes be confusing, and one of the most important guidelines pertains to ADU setbacks. To know where you can build your ADU and what size of ADU you can build, you first need to know the setbacks you need to maintain from your property lines. Understanding the side, rear, and front yard setbacks in your area is an important first step.
Here at GreatBuildz, a free service that connects homeowners in the Bay Area, San Diego, Los Angeles, Orange, and Ventura Counties with reliable ADU contractors, we speak to homeowners every day about specific ADU requirements like setbacks – read on to learn more.
What are the Minimum ADU Setback Requirements in California?
The setback requirements for building an ADU in California are generally 4 feet from the side and rear property lines.
This applies to most locations, but some cities like San Diego have even reduced this requirement to 0 feet in certain cases. Front yard setbacks are not established by the state and are set by each city. Keep in mind, per state laws, all these setbacks cannot prevent an ADU from being built (up to 800 square feet in size).
Are there Different ADU Setback Rules for Attached vs. Detached ADUs?
Yes, there are different setback rules for attached and detached ADUs in California. For detached ADUs, the setback requirements are 4ft from both the side and rear property lines. And the front yard property line is established by each city’s zoning code.
For attached ADUs, the same setbacks are the same as above in most cases, but there are exceptions because they are attached to the existing home. If the existing home has setbacks smaller than 4ft, the ADU can also follow these setbacks. And the same goes for the front setbacks; the ADU setback can follow those of the existing home even if they are less than what is generally required.
Can I Build an ADU within my Property’s Front Yard Setback?
In most cases, you cannot build an ADU within the front yard setback, but there are several exceptions. You may be able to convert an existing garage that’s located in the front yard, even if it’s within the front setback area.
Also, if you’re building an attached ADU, California law states that the setback requirements cannot preclude you from building an ADU up to 800sf, so you may be able to get a variance to reduce the front setbacks.
How do ADU Setback Rules Apply if I’m Converting an Existing Garage into an ADU?
If you’re converting an existing garage into an ADU, state law indicates that no additional setbacks are required. So, if you have a legally permitted garage, you can convert it into an ADU without being concerned about setbacks as long as the conversion stays within the existing footprint of the garage.
However, if you’re expanding or adding to the garage (adding first or second-story space), the newly built part of the structure would need to meet the 4-foot rear and side yard setback rule.
Do ADU Setback Requirements Change Based on the Size or Height of the ADU?
For single story ADUs that are no more than 16ft in height, the setbacks are the standard ones set by California law…4ft to the rear and 4ft to the side property lines. For two-story ADU or those taller than 16ft, some cities have more stringent setback requirements.
For ADUs up to 800sf, the state law requires cities to abide by the standard setbacks of 4ft to the rear and side property lines. For ADUs larger than 800sf, some cities may have setback requirements that are more strict than the standard state laws.
What are the Rear and Side Setback Rules for ADUs on Small or Irregular Lots?
The rear and side setbacks for small or irregular lots are 4ft to the side property line and 4ft to the rear property line. However, these setbacks are not allowed to preclude each property from building an ADU of up to 800sf. So, these setback requirements might be waived for small or irregular lots that would otherwise be impossible to build on.
Can Local Cities Require Larger ADU Setbacks than the State’s 4-foot Minimum?
No, local cities cannot require setbacks larger than 4 feet from the rear and side for any ADU planned up to 800sf. Cities are, however, able to dictate their front setbacks based on their zoning code. For ADUs that exceed 800sf, some cities could require more strict setback requirements.
Are there Exceptions to ADU Setback Requirements for Small or Urban Properties?
There may be exceptions to setback requirements for small or urban properties, as the state laws require cities to allow an ADU up to 800sf on every property. Therefore, cities have to maintain some level of flexibility with regard to setbacks for small or urban properties. Some cities, like San Diego, permit zero foot side and rear setbacks in some cases.
How do Setback Rules Apply when Adding a Second Story to an Existing Structure or Garage for an ADU?
When adding a second story to an existing structure or garage to build an ADU, the setback rules in California require a minimum of 4-foot side and rear setbacks. However, if you’re building an ADU larger than 800sf, the local city has some flexibility to require larger setbacks, especially for a two-story ADU that is up to 25ft tall. Some cities will allow the second-story ADU to meet the same setbacks as the existing structure, be it a garage or the main house (assuming they are already a minimum of 4ft).
Can I Request a Variance if my Lot Can’t Accommodate the Standard ADU Setback Requirements?
Yes, you can request a variance if your lot cannot accommodate the standard ADU setback requirements. but keep in mind this approval is not guaranteed because it’s at the discretion of the planning department or building department in your city. Based on California state law, every property should have the right to build an ADU up to 800sf and the city should not preclude this right. So in theory, a city should be willing to grant a setback variance if it otherwise makes construction of an ADU impossible on your property.
The bottom line is this: the state of California has set out a terrific framework that clarifies the allowable setbacks each city should adhere to when permitting new ADUs. And, many cities follow this guideline exactly. But some cities choose to be either more restrictive or more permissive with their ADU setback standards. So, the best way to determine the setback requirements that pertain to your property is to inquire with your local building department or speak with an experienced local architect.
If you want to be connected with a knowledgeable architect in your area, reach out the the friendly staff at GreatBuildz for a referral.
California ADU Laws that Include ADU Setback Requirements:
- SB 13 – established that local agencies must allow a minimum 4-foot side and rear yard setback for all ADUs. allows ADUs to be constructed within existing structures (such as garages) without requiring setbacks.
- AB 68 – specifies that local agencies cannot require a setback greater than 4 feet from the side and rear property lines for new construction of ADUs. Allows ADUs built within existing structures, such as garages, to maintain the same setbacks as the existing structure without requiring additional setbacks.
- AB 881 – reiterates the 4-foot side and rear setback rule and ensures that jurisdictions cannot impose setbacks for ADUs created by converting or replacing a legally existing structure (e.g., a garage).
- SB 897 – continues to enforce the 4-foot side and rear setbacks for ADUs but also allows local governments to require additional setbacks for ADUs larger than 800 square feet or over 16 feet in height.
- AB 670 – focuses more on HOA restrictions, it references that ADUs must adhere to the minimum state-mandated setbacks (e.g., 4 feet from side and rear property lines).
Frequently Asked Questions
What are the setback requirements for an ADU in California?
State law generally requires a 4-foot setback from the side and rear property lines for a new detached ADU. No additional front setback is required beyond your zoning. Converting an existing garage or building in its current footprint usually requires no new setback.
Can I build an ADU on my property line?
Not for new construction, which generally needs a 4-foot side and rear setback. However, if you convert an existing structure like a garage that already sits near or on the setback line, you can typically keep its existing footprint under state ADU law.
Do ADU setbacks vary by city?
The 4-foot side and rear setback is set by state law and cities cannot require more for a standard ADU. Other rules, like height and lot coverage, can vary, so check with your local planning department for the specifics of your property.
Choosing the right contractors is essential to a smooth, successful ADU building process that doesn’t go over budget. To be matched with a trusted, pre-vetted ADU contractors, contact GreatBuildz today at (818.317.3567) or visit our website for more information.
