The building of ADUs across California has risen sharply in recent years owing to a range of benefits these units can provide, such as increased housing and added valuation to existing properties. Given this surge in ADU construction, lawmakers across the state have continued to lay out the legal specifics of what homeowners can and cannot do when building an accessory dwelling unit. Size limits are a fundamental concern for those looking to build this kind of unit, so how big can an ADU be in California? Here, we take a look at what your limitations are across the state and cover the maximum ADU size limits in ADU hotspots such as Los Angeles.
ADU Minimum Square Footage California Requirements
California state law requires all accessory dwelling units to occupy a minimum size of 150 square feet. Once we get into maximum size limits, we’ll go into the varying types of ADUs, but this is only relevant here as the 150-square-foot rule applies to some types of accessory dwelling units.
If you plan to add an accessory dwelling unit to your property, you should always check local laws for your area, as some can differ. For example, in Los Angeles, an ADU must occupy a minimum size of 150 square feet, but you can apply for a discretionary permit to construct an accessory dwelling unit smaller than this.
However, ADU size laws are pretty hard and fast, so getting accepted for such a permit will prove to be a challenge in Los Angeles. Most requests are denied.
Max ADU Size California
As we have just mentioned, we need to drill down into various types of accessory dwelling units to give you the most accurate information about maximum ADU size limits.
Detached ADU Size Limitations
Regardless of which area of California you live in, you’ll find that a detached unit can be built on as much as 800 square feet of land. If you plan on building an 800-square-foot detached ADU, the requirement is that it must be less than 16 feet high and have 4 feet of clearance at the rear and sides.
Not all Californian homeowners are bound by the maximum lot size of 800 square feet. In fact, of the 482 cities in California, 391 of them will allow for a detached ADU that occupies 1,200 square feet of space. Additionally, around 150 counties and cities will allow you to construct a detached ADU up to 1,000 square feet in size.
You must check your local ADU ordinance so that you have a full understanding of what your limits are and what requirements you must complete to stay within the law. For example, you can construct a detached accessory dwelling unit up to 1,200 square feet in Los Angeles.
However, the ADU size can be at most 50% of the primary dwelling unit. Check with local authorities for their rules around a detached ADU before you kickstart the project.
Attached ADU Size Limitations
The attached ADU size limits are similar to those of detached ADUs, with minor differences. ADUs connected to the existing primary residence must have a minimum of 150 square feet of floor space up to a maximum of 800 square feet.
The minimum dimension of any room within the attached ADU is 7 feet in any horizontal direction. The key difference between an attached and detached ADU is that the maximum size of an ADU mustn’t surpass 30% of the living area of the primary dwelling.
Junior ADU Size Limitations
Unlike regular ADUs, which can be constructed on a multi or single-family dwelling or even agricultural areas, a junior accessory dwelling unit is built solely on the existing space on the property of a single-family residence.
JADUs are allowed in any area of California that allows a single-family dwelling. Regarding their maximum size, this kind of ADU must occupy at most 500 square feet.
Depending on local ordinances, junior accessory dwelling units are subject to minor rule changes. In Los Angeles, a JADU must be contained within a single-family residence. These units must be no bigger than 500 square feet and can be attached to the existing structure or detached.
What Is The Best Size for an ADU?
What is the ideal ADU size for your property? That depends on numerous factors you must consider during the planning stage. Here are some considerations you must make if you wish to build an ADU in California.
Eventual Use of The Accessory Dwelling Unit
The first decision to make is what type of ADU you are looking to construct and what will be its primary purpose. This will help you to decide whether it will be attached to an existing structure, whether it will be a JADU, or if you prefer detached ADUs.
You can use ADUs to offer complete independent living facilities for one or more persons and create a two-bedroom ADU to generate rental income or house elderly family members. Alternatively, you could make a JADU for single-person occupancy.
Budget Considerations
As a general rule, the larger the construction size, the more expensive the project will be. This, again, will dictate just how many square feet, within the rules, of course, you want the ADU to be.
Additional considerations that can affect the square footage include the need for a separate septic tank and separate utility connections if the ADU isn’t connected to the existing structure. These cost extra money and affect your ability to scale up.
The Space Available
When mapping out how large the ADU will be, you have to consider all legal requirements, not just the minimum and maximum size. For example, the required yard setbacks from the property lines could restrict how large your ADU is.
ADU Rules and Regulations
Finally, as we have discussed here, the ADU rules and regulations will always dictate the maximum size limits for your project. Pay attention to the size percentage of your existing property, any ADU laws around utilities, parking rules, and, of course, maximum unit size.
How Many ADUs Can You Have in California?
Under the new ADU laws, the limit for how many ADUs a single-family residence can have is up to 2 ADUs on the property. This includes one JADU, one attached ADU, or one detached ADU and one JADU.
The yard setbacks remain the same, and the general rule across the state is that 800 square feet is the maximum size. Since owner-occupancy laws don’t kick in until 2025, these can remain empty once the building is completed.
What Build Method Can Do For You
Constructing an ADU in California is now easier than ever. However, finding the right construction team for your project is crucial, whether you’re building a junior accessory dwelling unit, detached, or attached ADU.
Here at Build Method Construction, we have a great team of experienced and dedicated contractors who work tirelessly to guide our clients in selecting the perfect ADU for their property based on their individual needs and budgets.
We offer support with design, acquiring permits, making structural upgrades, and easing the burden of complying with California’s local laws and building regulations. If you’d like to plan your own ADU project, please call us today for a free quote to get the ball rolling.
FAQ
What is the new ADU law in California in 2023?
The new ADU laws introduced in California have increased the maximum size of an ADU to 800 square feet. The state has also given local authorities more flexibility, allowing areas like Los Angeles to offer up to 1,200 square footage for new ADUs. In addition, attached ADUs may be constructed as high as 25 feet if connected to the primary dwelling under new laws.
Can you build a two-story ADU in California?
In some areas of California, like San Diego and Los Angeles, you can build a 2-story ADU if it doesn’t exceed the maximum height of 16 feet.
What is the minimum lot size for an ADU in California?
The minimum lot size for an ADU across California is 150 feet. Permission may be granted for a smaller ADU, although these requests are often rejected.
Do you need a permit to build an ADU in California?
You will require a permit before planning and constructing any type of ADU across California. You will also need on-street parking permits and cover utility fee requirements. Failing to do so will see you face fines and problems with insurance and run the risk of lawsuits from any tenants.
