Since the people of California are struggling with homelessness, the rate of housing production has become below compared to the demand rate. This is why the development of ADUs in California is on a high rise.

In general, ADUs (Accessory dwelling units) are attached or detached dwelling areas that are constructed to provide income opportunities. In addition, some people prefer to build ADUs for their loved ones. However, California prohibits such untraditional houses from exceeding certain size limits.

According to California state laws, an ADU should have a floor area of up to 800 square feet, a 16-foot ceiling height, and a 4-feet setback distance. However, ADUs can be larger in certain places, with certain restrictions.

So, do you want to know – how big an Accessory Dwelling Unit (ADU) can be in California? What are the ADU size limits in Los Angeles city, CA? The following write-up is going to answer this question – doesn’t matter which area you live in California. We also reference some laws in this article of the official HCD (California Department of Housing and Community Development) ADU handbook. Let’s have a look!

The Maximum Size Limits of Different ADU Structures

In the state of California, adu maximum size can be different based on type of ADUs you building. Here are the four main types ADU and their mini and max size allowed to construct in California:

ADU Size Limits in California

  • Detached ADUs Size Limits

It doesn’t matter what area of California you live in, detached ADUs in California can be built up to 800 square feet, as long as they’re less than 16 feet high and respect 4 foot rear and side yard setbacks.

Approximately 391 cities and counties allow detached ADUs up to 1,200 square feet according to California state law. Nevertheless, other cities and counties have stricter requirements.

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And, about 150 cities and counties restrict the size of detached ADUs. You’ll likely be limited to 1,000 square feet if your ADU has two or more bedrooms. There is a possibility that a detached ADU with only one room is limited to 800 square feet because of factors such as the size of the lot and the area covered.

  • Conversion ADUs Size Limit

If you’re planning to convert an existing space or primary dwelling – for example – a garage – there are usually no size restrictions. That’s because the structure already exists. Whenever there are restrictions on size, the maximum size is often determined by the largest accessory structure in the jurisdiction. However, if you plan to convert a structure into a JADU (junior ADU), it must not exceed 500 square feet in size.

  • Attached ADUs Size Limit

If you’re going to build an attached ADU in a primary residence or new ADU, its square footage can’t exceed 50% of the home’s square footage. Additionally, the attached ADU size in Los Angeles city limits also involves that it can’t exceed the house’s height.

  • Internal ADUs Size Limit

Internal ADUs are normally built inside of existing homes, usually within the existing floor plan. Therefore, there aren’t enough general rules for them, just that they have to be within the pre-existing home.

Keep in mind that the above-mentioned rules are general. Every city and county has different regulations that could differ from the ones mentioned above. For this, you can ask our professional general contractors of Lux Construction Group who are well-versed with every rule and regulation related to your county in CA.

How big of an ADU can you build?

As defined in Section 17958.1 of the Health and Safety Code, the minimum size for an ADU must be at least 150 square feet regardless of the ADU type. But there are exceptions. If you want to build a smaller ADU, you can apply for a discretionary permit, but there is a good likelihood that you will not be approved.

Preferred size for ADUs in Los Angeles

Till now, we’ve gone through what would be the maximum and minimum size of ADUs in California. But, there is one thing that everybody should be aware of for building an appropriate and best ADU in California.

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We know that everyone is tempted to go with a bigger ADU. However, we here recommend building your ADU under 750 square feet. There are various reasons for it:

  • Constructing an ADU under 750 square feet is exempt from impact fees.
  • ADUs that are less than 800 square feet don’t have to comply with the bulk and massing development limitations, such as FAR, open space, and lot coverage (i.e., lot coverage, open space, and minimum lot size).
  • In most cases, adding an extra 50 square feet doesn’t justify the additional costs, restrictions, or hassle.

Having these regulations waived can make planning and development processes much easier. Even, most of the top-selling ADU floor plans and prefabricated homes are smaller than 750 square feet. The cost of building an adu in Los Angeles not only impact by size but also other factors like design, type of adu, etc.

ADU Construction Rules In Los Angeles

In California, there are approximately 482 cities and 58 counties. And each of them has different rules and regulations when it comes to ADU size limits.

We’ve brought this section for folks who are in hurry and need only precise information about an ADU size limit in Los Angeles, California. Read this section if you want to build an ADU on your property.

Based on the size you required to build an additional dwelling unit, you need permission from local regulatory. And there is the cost of ADU permit in Los Angeles. Most of the time your contractor will help you in taking all permits and permission for constructing an ADU.

Which Jurisdiction Does Your Property Reside In?

As we’ve mentioned above, there are 539 different jurisdictions (58 counties, and 482 cities) in California. And, each has different size limits, depending on the jurisdiction in which you reside or your property. So, while planning to build an ADU, we recommend figuring out your jurisdiction and then finding out whether it’s on the list of jurisdictions that have approved local ADU laws. If yes, sent them to the HCD.

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What If Your Jurisdiction Has Its Own Limits on The Size of Adults?

If your jurisdiction is on the list, you should look that up and determine your maximum ADU size limit in California. These ADU ordinances may have any of the following effects:

  • Some jurisdictions actually allow detached ADUs that are larger than 1200 square feet.
  • You just have to repeat the state law restriction of 1200 sq ft.
  • The restrictions can be tightened to a certain extent.
    1. Everyone can build an ADU 800 up to square feet.
    2. If there are no lot coverage, FAR, or minimum lot size requirements, homeowners should be able to build an 850 square foot detached ADU.
    3. A 1000 square foot detached ADU should be possible if you have 2+ bedrooms, FAR, and minimum lot size requirements aside.

In the California government code section, local jurisdictions have the right to adopt limits on the size of ADUs up to a certain point.

What If Your Jurisdiction Isn’t on The List, But Has a Size Limit?

A number of jurisdictions are passing ADU size limits without submitting their ordinances to the HDC. How? We explained this in the following section. Take a look!

  • Follow The City/County Size Limits

Working or following the city or county’s size limits will help in achieving your goals. In this, the planning department or city manager will help in building your ADU.

  • Speak to the HCD or An Attorney

You can also contact the HCD or an attorney to find out what options you have. The case may be different. In this scenario, you can contact your local professional ADU contractor or ask HCD specialists.

Write to [email protected] with the details of your situation including the address and any correspondence you think necessary to tell us or the challenges you’re facing with your jurisdiction.

Please note that the above rules aren’t specific as they might change over time. That’s why you need to stay alert and in contact with your local general ADU contractors. And, if any city/county adopts a Los Angeles ADU ordinance, they have 60 days to send those ADU laws to the HCD for approval. So, this rule list can get changed.

Ask ADU Construction Expert

If you’re unable to figure out all the rules and regulations regarding building an ADU, it’s time to talk to ADU professionals. They are well-skilled and proficient, helping with obtaining the necessary building permits and explaining in detail your city/county’s size limit to build affordable housing.

We are Los Angeles based adu construction company, have years of experience in developing well-structured ADUs. Ask us anything! We offer a free consultation and navigate you through appropriate ADU planning aspects and ADU size limits in Los Angeles.

So, reach us today and plan out your entire ADU project with us along with affordable ADU costs!