ADU Setback Requirements

What Are ADU Setback Requirements?

Setback requirements tell you how close to a property line you can build an accessory building (like an ADU). These requirements ensure separate structures don’t encroach on an adjacent property, and maintain the neighborhood’s “curb appeal.”

In California, setback requirements cannot exceed 4 feet from the rear property line (boundary at the back of a property) and the side property lines (boundaries on either side of the property).

This is true no matter how many square feet your ADU is, and there is no minimum unit size. These development standards were streamlined to prevent a city’s zoning codes from becoming too restrictive, which could hinder the development of ADUs.

When it comes to the front property line, cities are able to determine their own setback requirements. These usually follow the same setback requirements as for a single-family home.

In the case of corner lots, where two sides of the property open up onto a street: The primary street-facing side (usually where the front door is located) must meet the city’s front setback requirements. The secondary street-facing side has its own setback requirement, which is determined by the city and may exceed 4 feet.

Proper setback planning avoids costly delays—always verify local zoning rules before breaking ground.

What are the Setback Rules for an ADU in California?

Rear and Side Setback Requirements for ADUs

Side and rear yard setback standards for ADUs are easy to figure out: California’s AB 2221 says cities can’t mandate an ADU sit more than 4 feet from the side or rear property lines. This means that if you’re building an ADU on your property, it’ll likely have a setback requirement of 4 feet – with some exceptions.

As we mentioned, corner lots are one: AB 2221 leaves these to the city to decide. Another is the conversion of an existing structure or “non-habitable space” into an ADU. For example: If you have a detached garage that’s less than 4 feet from the side or rear property line, and you want to convert it to a detached accessory dwelling unit, you can. The city will honor the existing setbacks. This is even the case if you knock down an existing structure and rebuild an ADU in its place.

Front Setbacks for ADUs

To determine the front setbacks for your ADU, you’ll likely need to contact your local building department or work with an ADU builder familiar with the zoning requirements throughout the San Diego area.

Cities are allowed to set their own front yard setbacks, and these often mirror the requirements for primary units. This means that the front yard setback is usually the same for your main house as it is for your ADU.

If your primary residence sits back on your property, leaving little yard space, this can be a challenge. By working with an experienced ADU builder, though, you may discover workarounds you hadn’t thought about, like building an attached ADU as opposed to a detached structure or even converting unused space in your home into a junior accessory dwelling unit or JADU.

How Far Does an ADU Have to Be From a House in California?

California law also doesn’t explicitly outline how far an ADU needs to be from your primary residence. This is left up to the local building departments. Typically, it’s around 5 feet. This is to account for fire safety and to prevent fire from spreading too quickly from your existing single-family home to your ADU, or vice versa.

If you’re worried about meeting this requirement, you may want to pursue an attached ADU. They can not only help you navigate this setback but also come with some cost savings compared to a detached building.

California’s 4-foot side and rear setback rule simplifies placement—leverage this flexibility for smarter layouts.

Local Variations in ADU Setback Requirements

Municipalities in San Diego not only have differing setback requirements when it comes to the front property line and distance from the single-family residence, but they can also have different requirements for easements.

There are many types of easements. An access easement gives someone the right to pass over or through another person’s property to access their own. This is common when it comes to driveways and parking spaces (especially tandem spaces). A utility easement allows utility companies to install or maintain utility infrastructure. A drainage easement allows water to flow through a property to prevent flooding, and a conservation easement preserves yard space for environmental or historical purposes. Conservation easements are common in historic districts.

Many times, if your property has some sort of easement, you can’t build an additional unit over it even if it meets the general setback requirements. If you aren’t sure if your property contains an easement, contact your local building department. They can tell you if you have an easement and if it involves permanent provisions (also sometimes known as appurtenant provisions) or if the restrictions are temporary.

Setback rules vary by city—partner with a builder who understands hyper-local zoning nuances.

Greater San Diego Setback Requirements

Below you’ll find the side, front, and rear setbacks for cities in the San Diego area, as well as a link to each city’s zoning department to verify this information (since requirements can change over time).

Remember, these requirements are minimum setbacks. This means that your accessory building must be at least this far back from a property line, but it can also be further.

Factors That Influence ADU Setback Requirements

The standard setback requirements (4 feet from the side and rear property lines and 5 feet from an existing house) are done to preserve “curb appeal” in a neighborhood and maintain fire safety.

There are other factors that influence these setback requirements and can even cause exceptions. We mentioned how corner lots and easements can create additional setbacks for property owners, both literally and figuratively. Other exceptions include the slope and topography of your lot and if you live in a flood zone or wildfire zone. If your yard is sloped or you live in an area prone to flooding or wildfires, larger setbacks may be put in place for safety.

The shape of your lot also comes into play. While there’s currently no minimum lot size for ADU builds, the shape of your lot and the placement of your existing single-family residence may make it hard for you to meet setback limits. In these cases, property owners may be able to apply for a variance.

A variance is an exception to a city rule. Variances allow homeowners to modify setback requirements to build an ADU of reasonable size. While lot shape is the most common reason for a variance, they can also be given on the basis of hardship. For example, if you’re building an ADU to use as a granny flat or in-law suite for aging parents with mobility issues, exceptions may be made to ensure that any independent living facility is accessible.

Lot slope, easements, and fire zones can change the rules—evaluate your site holistically before designing.

How to Maximize Space While Meeting Setback Requirements

If you don’t have grounds for a variance or your variance doesn’t get approved by the city after a public hearing, there are other options available to help you maximize space while still meeting setback requirements. Attached ADUs, JADUs, and conversion ADUs like garage conversions are options that can not only get you around setback requirements but also save you money on your build.

Another option is to obtain a building permit for a 2 story structure. 2 story structures can expand the total square footage of your ADU while minimizing the footprint on your yard. For example, your 2 story detached unit can be 1200 square feet in size (which is the maximum size for an ADU in California) while only taking up 600 square feet of yard space.

Some cities don’t allow 2 story ADUs, and others only allow them if the existing single-family dwelling unit is also 2 stories. For those that do allow them, there are height limits to consider. Generally, the maximum height for 2 story ADUs is between 20 and 25 feet.

If a 2 story ADU isn’t allowed in your city or is outside your budget, the best thing you can do to maximize your space is good architectural design. With an efficient layout and smart interior design choices, even efficiency units as small as 400 or 500 square feet can provide all the provisions for living as a larger residential dwelling unit.

Strategic floorplans and vertical builds can help you stay within setbacks without sacrificing livable space.

Why Working With Professionals Is Crucial

If you’re looking to transform your residential property with an ADU development project, it’s essential to work with a professional like Better Place Design & Build. We can get you the livable space you need without any of the costly setbacks that come from not meeting the minimum setback requirements and development regulations for your city.

We make it our goal to ensure a stress-free build process, from the initial consultation to the design process to the final finishing stage. Take a look at some of our ADU construction plans to see what’s possible for your build, then reach out for a free consultation.

A knowledgeable ADU builder helps you meet all regulations and makes the most of your square footage.