What Is an ADU? A Guide To Accessory Dwelling Units in Los Angeles [Updated 2023]

(Updated August 2023)

So, you’ve heard about ADUs in Los Angeles, eh? Maybe a friend was talking about her ‘granny flat’ or ‘casita’, you saw your neighbor recently did a garage conversion, or perhaps you overheard your coworkers talking about their latest investment opportunity. Well, thanks to some updated regulations in California, many homeowners can now legally create accessory dwelling units on their property.

Here at GreatBuildz, a free service that connects homeowners in Los Angeles, Orange County, Ventura & San Diego with reliable general contractors, we get inquiries every day about ADU projects – here are some key points you need to know.

The term ADU, otherwise known as an Accessory Dwelling Unit or Additional Dwelling Unit, is defined as a secondary housing unit with independent living facilities, on a residential lot in addition to the main house.

Recently, both in California and in Los Angeles, these ‘dwelling units’ have been getting a lot of attention as both the city and state have drastically relaxed the restrictions and rules around building ADUs. This has created a boom of interest by homeowners around building such ADU units in their backyard or converting their garage into a living space.

ADU - Accessory Dwelling UnitDetached ADU in California | Credit: valleyhomedevelopment.com

What you need to know about Los Angeles ADUs: There’s a New Law In Town

Let’s briefly discuss the guidelines which have recently changed to make accessory dwelling units much more viable for many homeowners. As one method to help assuage the housing crisis, the state, along with many California cities, has eased many previous restrictions to building these structures.

To simplify this article, I’ll be discussing the guidelines specific to Los Angeles ADU ordinance, so please keep in mind that other local cities will likely have their own set of rules. If you’d like to read about ADU regulations in other areas, see my articles on:



  • Parking – Probably the most drastic change has been to the parking requirement. Whereas previously the city required off-street covered parking (garage, carport) for both the existing home and any new living structure proposed, the guideline now allows the main house parking to be uncovered (ie. the driveway) and ZERO parking for the additional ADU unit, as long as it’s near transit.
  • Increase in maximum permitted size – you are allowed to build up to 1,200sf ADU, and the minimum allowed in all cases is 800sf.
  • Greater variety of types of ADUs allowed – this includes garage conversions, stand alone ADUs, attached ADUs, detached ADUs, and in some cases two story ADUs
  • Some impact fees are being waived to encourage homeowners to build – for more information, read this important memo from the LA Department of Building and Safety about ADUs

It’s also important to note: ADUs don’t require any ‘discretionary’ approval, meaning that you don’t need approvals from city planning dept, neighbors, planning boards, etc, as long as you meet the established guidelines. So, getting the right to build an accessory dwelling unit in Los Angeles is just a matter of submitting plans to the building department and going through the plancheck process to obtain an ADU permit.

Make sure to research the City of Los Angeles ADU ordinance for more information on the requirements and regulations of building an ADU. 

Build an ADU for extra income

Build a secondary suite for extra income.

Why build an ADU on your property?

Many homeowners are excited about the simplified restrictions and are now exploring building an accessory dwelling unit on their property, but why? I’d say it comes down to two things: their new ability to add living space to their property in a simplified manner, coupled with the tremendous variety of potential uses for an ADU.

Adding square footage to an existing home in the past meant building an ‘addition’ or second story, which was a headache. Not only was it often very costly, time-consuming, and usually required considerable changes to the existing layout of the home, but it also meant living through the discomfort of construction in your home.

An accessory dwelling unit relieves many of these problems and allows for a ton of flexibility in uses. People are building them to use as extra space (an office or guest house), a music or yoga studio, a mancave or she-shed, or a home for their retired parents or grown children.

Beyond these ‘typical’ uses, it’s also an opportunity for a homeowner to use as a rental unit for additional income. I’ve heard from several soon-to-be retired homeowners planning to build an ADU in Los Angeles so they can move into it (as they don’t need as much space) and rent their primary home as a source of retirement income. That’s pretty ingenious.

What kind of ADUs are there?

The two primary options are either building a new ADU unit in the backyard or converting an existing garage to an ADU. A garage conversion is the most cost-effective option because the basic structure already exists. The downside is the limitation in size – most 2-car garages are only 300-400 square feet.

This is still enough space for a ‘studio’ or small one-bedroom unit, with both a kitchen and a bathroom. Alternatively, you could build an addition to your garage and convert the entire space to an ADU, which is a cost-effective way to create a larger ADU with 600-800sf and 2 bedrooms.

A new ADU, however, can take many forms.

It can be attached to an existing home, attached to a garage in the rear of the lot, or detached completely.

Garage Conversion ADUGarage Conversion ADU  | Credit: accessorydwelling.com

It can typically be one or two stories, with a maximum height of either 16′ or 25’ (depending on location).

Second story ADUSecond story ADU  | Credit: buildinganadu.com

It must be in the backyard or side yard area and not in front of the existing home. A new detached accessory unit is limited to 1,200 sf, while an addition attached to an existing home is limited to the lesser of either 1,200 sf or 50% of the size of the existing home.

A 400-600sf ADU is ideal for a one-bedroom floor plan and a 600-1,200 sf structure is enough to be one or two stories, with up to three bedrooms and multiple baths!

Note: An existing garage that is in front of the home may also be converted to an ADU. Or an existing attached garage can be converted to a Junior ADU.

Detached accessory dwelling unitDetached ADU in backyard  | Credit: buildinganadu.com

Who can build an ADU?

The city of Los Angeles ADU ordinance has allowed ADUs on most residentially zoned lots regardless of their size as long as the structure meets the basic restrictions and there is an existing home already on the property (with only minor exceptions), meaning most LA homeowners have an opportunity to add an ADU on their property. With regard to parking, an ADU is exempt from any parking requirements as long as the property is within one-half mile of a public transit (bus stop, etc).

Los Angeles ADU’s are also allowed on multifamily properties such as duplex, triplex, four-plex, and apartment buildings. These properties generally have different guidelines for the construction of ADUs, but they also have the potential to build several ADU’s on a single property.

If converting an existing garage into an ADU, two spots need to be maintained for the existing residence but can be uncovered spots on a driveway, which can be side-by-side or even tandem. A new accessory dwelling unit must be at least 10’ away from the existing house and garage or it must be attached to either. Also, a new unit must be at least 4’ from both the rear and side property lines. A garage conversion into a living space, however, does NOT need to meet these setback requirements.

ADU entertainment room

ADU’s are perfect for movies & sports.

How much does an ADU in Los Angeles cost?

An accessory dwelling unit cost will vary greatly in cost based on the options and size you choose. As discussed, the most cost-effective option is to convert an existing garage into a ADU garage conversion.

Since the major components already exist, the construction entails items such as constructing the fourth wall (where the garage door is currently), adding the interior components such as interior walls, a kitchen, bathroom, flooring, etc; adding windows and doors, plumbing, electrical, HVAC, insulation, and a new sewer line that will probably connect to the sewer lateral at the front of the main home.

The cost for an ADU garage conversion can usually range from $95,000-$120,000 depending on the homeowner’s requirements. Costs to construct a new accessory dwelling unit in Los Angeles can also vary considerably based on size, the number of stories, location, access, etc, but will generally range from $150,000-$400,000.

A safe rule of thumb is to assume $250-$400 per square foot – the bigger the space, the lower cost per square foot. If you’re considering ‘building up’ for a 2-story ADU, costs will go up considerably as well. Keep in mind that ADU cost also can vary greatly depending on the quality and style of materials you plan to use. ADU cost will be affected by both interior materials (flooring, kitchen cabinets, tile, lighting, etc) as well as exterior materials such as roofing, stucco/siding, hardscape & landscape. Finally, ADU costs are affected by things like ADU permit cost, city requirements or fees, and the proximity to utilities on your property. For ADU cost-saving ideas check out this blog (link). 

How much does a pre-fab ADU cost?

Pre-fab or modular ADUs are getting a lot of attention recently. These homes are mostly constructed in a factory, shipped to your location, and assembled on-site. Quite a few new companies have popped up that manufacture these pre-fab ADUs, which often come in several floorplans and design options. Some are ultra-high-end and expensive while others are meant to be entry-level.

Pre-fab ADUs have some advantages and some disadvantages to traditional ADUs built onsite by general contractors. In terms of cost, they can initially seem cheaper than traditionally built ADUs, but it’s really important for consumers to include ALL the costs (not just the unit) such as taxes, shipping, craning, assembly, installation, permitting, utility connections, & foundations.

ADU Office

Use an ADU as a quiet, comfortable office.

How do I pay for an ADU?

Homeowners have multiple ways to finance their accessory dwelling unit project. Obviously, they can pay for it from their own savings. Or they can finance this construction by taking out a home equity line of credit, securing a construction loan, or using a home renovation loan which is often a very quick process, but comes with a higher interest rate, from a company like Lightstream or SoFi. There is also an interesting renovation loan program from a company called RenoFi, who will base your loan amount on the ‘post-construction’ value of your property, allowing you to borrow more than traditionally available.

There are quite a few financing options for ADUs now, so it just depends on your needs. This ADU financing blog provides the details on many top options for ADU financing.

Process and Timing

How long does it take to build an ADU?

As you can imagine, the timing is different for an ADU garage conversion versus a new construction project. For an ADU garage conversion, you can expect the entire process to take 5-6 months, which includes the time to design the architectural plans, wait for the city to conduct plancheck, and finally, the construction process – which will take about 2-3 months.

A new accessory dwelling unit will take longer for city plancheck and require a longer construction process, so you can expect the entire process to take 6-9 months, with the construction phase lasting 3-6 months.

ADU for aging parents

Build a granny flat as a safe environment for aging parents.

If you already have an ‘unpermitted’ ADU or garage conversion, it’s currently a good time to get the appropriate ADU permits and construction completed to get this structure up to code and legalized. Once you complete this work, the city will issue you a Certificate of Occupancy for your ADU, which will make the space legal to rent and add value to your property upon sale.

The process will be similar to that above, but you’ll probably need to perform a lot less construction to legalize your ADU or garage conversion, so the timing will be shorter. Check out our full blog about legalizing a garage conversion or ADU.

What is the process of building an ADU?

The process usually begins with the homeowner meeting one or more experienced contractors, who come to the home to discuss the project and provide some insights about the location constraints, size, design, estimated costs, etc. Once the owner and contractor are on the same page about the desired parameters, either one can bring in an architect or plan designer to prepare the plans.

Once the plans are finished and approved by the owner, the contractor(s) will do a detailed estimate and bid. Next, the owner will select their desired contractor and sign an agreement for the work. Either the architect or contractor will submit the plans to the building department for plan check and manage the process until a building permit is issued. Finally, construction can commence. Don’t forget to obtain homeowners insurance to cover your new ADU or garage conversion.

If you live in a community with a Home Owners Association (HOA), you should inquire about their requirements and standards to build an ADU. They cannot preclude you from building an accessory dwelling unit (per new CA law AB 670), but they can require you to meet the various design guidelines enshrined in the HOA Bylaws and CC&Rs. Knowing these standards up-front will help your architect design the plans for the ADU correctly, and allow for an easier approval process with your HOA board or design committee.

Finding The Right Team – How do I hire a good Los Angeles ADU contractor?

When looking to build an accessory dwelling unit or even starting to explore the idea, it’s best to search for only local, licensed General Contractors. No other contractors are qualified or equipped to do this sort of construction, and using an unlicensed contractor or handyman would be a mistake.

Any contractors you contact, always confirm they have experience with these types of projects. It is best to hire a contractor who’s built additions and garage conversions in the past and knows the potential issues/pitfalls. There are several other important criteria you should use in selecting a contractor, not including their cost estimate.


How about your own ADU gym?

Other things to look for in a contractor include:

  • Check for a valid contractor’s license

It’s extremely important to check their license on the Contractors State License Board website to confirm it is active, there are no disciplinary actions, and it has Workers Compensation insurance associated with it (assuming the GC has employees).

  • Make sure they’re insured

Always ask the contractor for a copy of his insurance certificate and make sure that it hasn’t expired. It might be a good idea to call the insurer directly, just to be sure. There have been cases reported where uninsured contractors have ‘Photoshopped’ their insurance papers to trick homeowners, so you can never be too careful.

  • Check their references

Ask your contractor for at least three references you can call. It’s important to ask them about their experience and satisfaction with the quality of the contractor’s work. If you can get any pictures of the work, even better.

  • Read their reviews online

It’s also a good idea to do a Google & Social Media search of the contractor to ensure there are no major red flags. Read any reviews you can find about their business, and don’t be afraid to address what you found with the contractor if there is anything concerning.

Building an ADU is not dissimilar to building a small home. Therefore, it’s super important to interview multiple ADU contractors in Los Angeles. The planning, permitting, and construction of an ADU is a long process, so the ADU contractor you select and hire will be “in your life” for a long time. You can be certain there will be cost overruns and delays, so ensuring that you’ve hired an honest and trustworthy ADU contractor will make a big difference during the process. The right contractor will be upfront and communicative with you.

At GreatBuildz, we screen all contractors upfront using our ten-point vetting process. We suggest everyone else take these steps as well before hiring an ADU contractor. I’ve written a longer article on the topic of hiring an ADU contractor. If you’re currently in the process, take a look at the rest here: https://www.greatbuildz.com/blog/find-an-adu-contractor-10-tips/

New ADU Laws for 2023:

AB 2221 aims to clarify and explain past legislation. One of the significant laws introduced in 2020 was the requirement that cities must approve or refuse permit applications within 60 days. Some planning offices have started to reject applications after the time has expired.  To rectify the problem, AB 2221 mandates that localities must provide all the reasons for refusing applications, and cities are required to consider applications more thoroughly. The height limit for ADUs is defined in this law, where all municipalities must permit ADUs to be at least 16 feet tall. The law specifies that front setbacks qualify for state exemption, and many limitations cannot be enforced if they hinder the construction of ADUs smaller than 800 square feet.

SB 897 removes the ban on constructing ADUs on properties with unpermitted construction unless the unpermitted work poses a threat to public health or safety. The law now requires communities to issue demolition permits when ADU permits are approved, and the construction of an ADU will no longer require the installation of fire sprinklers in the principal residence.

AB 916 permits homeowners to convert an interior area in their principal residence into a bedroom without a public hearing. Although this measure does not specifically address ADUs, it was initially written with ADUs in mind.

SB 9 – Although its not exactly about ADUs, In Los Angeles, SB 9 permits qualifying property owners to split their lots into two distinct parcels and erect a maximum of two additional residential units on each parcel. Before SB 9, homeowners were allowed to build a single home along with one ADU and one Junior ADU. Thanks to SB 9, homeowners now have the opportunity to construct two homes, two ADUs, and two JADUs on a single lot.

Additional Considerations:

Here are a few other things to consider when building an ADU:


ADUs are generally small and often don’t include a garage, so it’s important to include areas for the storage of various belongings. Storage areas can include built-in cabinets, closets, attics, or even outdoor sheds, etc.


Since an ADU is a full living unit, including laundry machines is a pretty important component. It’s not ideal to have the ADU share laundry with the main home or have to use a laundromat.


You’ll want to include an effective dual heating & air-conditioning system in your ADU, so you are comfortable year round in the unit.

Kitchen island

It’s hard to squeeze in a kitchen island, but it’s a huge bonus if you can make space for it in the kitchen. Even a small island makes a kitchen more usable and elegant. Also, it’s very practical as it can be used as both a kitchen prep area as well as an eating table.

Outdoor area & patio:

It’s important to consider creating an outdoor private space for the ADU, as long as it’s a usable area. Creating a concrete patio or installing pavers makes for a good surface for some seating, etc. A few potted plants and flowers are a nice touch, and a lawn is unnecessary. Adding a patio cover is a very nice detail to create shade, but it may not be cheap.


It’s a good idea to create some privacy between the main house and your ADU by constructing fencing or a wall between the two. Ideally, you’ll also want to build a separate gate that can be used solely by the ADU occupant for their access.

Natural light:

ADUs are small and a good way to make them feel bigger is to ensure lots of natural light is available to the unit. This can be achieved with many windows, skylights, or glass patio doors.


If you decide to build a new detached ADU in your backyard, you will now be required to add solar on the roof. This may add additional time to your construction schedule. Ask your contractor to plan ahead for the solar installation, and include the costs in your total estimate. If you are doing solar, you might consider making your ADU all electric (no gas) to take advantage of this…so you’d make sure to install an electric range, electric ware heater and electric furnace.


Especially in the case of attached ADUs, you’ll want to make sure there is appropriate separation, insulation, and/or soundproofing material between each unit/home so that the occupants aren’t hearing noise coming from next door.


There are many ways to make an ADU more comfortable for your tenant. One way is to incorporate ottomans as they are a great place to rest your feet and also store things.

In addition, fold-down tables are great as they also conserve space but can be useful for many different purposes. Another thing to keep in mind is to use pocket doors, as they can divide rooms without there actually being a room while also conserving space. Cabinets and hangers are also good to implement inside the ADU for extra storage space as well. Tankless water heaters are commonly used in ADUs to help save money and space. Futons and daybeds can be dual-purpose and further conserve space. Using hooks in kitchens and bathrooms is a good way to conserve more space. Storing things under beds conserves space.

When it comes to finding the best ADU and garage conversion contractor in Los Angeles, Orange County, Ventura, or San Diego – GreatBuildz is simplifying the contractor search. GreatBuildz is a free service that connects homeowners with reliable, thoroughly screened general contractors and provides project support from start to finish.

Call now (818.317.3567) to chat with a real person about your next renovation project or visit our website for more information: www.greatbuildz.com

ADU Frequently Asked Questions

Additional ADU Resources:


https://www.hcd.ca.gov/policy-research/docs/ADU-guide-web-singles.pdf (from AARP)


Accessory Dwelling Unit Guidelines for Every City in Los Angeles

Los Angeles County Cities hide
  • Los Angeles City ADU Guidelines


  • Santa Monica ADU Guidelines


  • Beverly Hills ADU Guidelines


  • Long Beach ADU Guidelines




  • La Mirada ADU Guidelines


  • Glendale ADU Guidelines


  • West Hollywood ADU Guidelines


  • Burbank ADU Guidelines


  • Inglewood ADU Guidelines


  • Torrance ADU Guidelines



  • Whittier ADU Guidelines


  • Calabasas ADU Guidelines


  • Culver City ADU Guidelines


  • Norwalk ADU Guidelines


  • La Verne ADU Guidelines


  • Santa Clarita ADU Guidelines


  • Downey ADU Guidelines


  • Manhattan ADU Guidelines


  • La Canada ADU Guidelines


  • Redondo Beach ADU Guidelines


  • Hawthorne ADU Guidelines


  • San Gabriel ADU Guidelines


  • Carson Capistrano ADU Guidelines


  • Arcadia ADU Guidelines


  • El Monte ADU Guidelines


  • Gardena ADU Guidelines


  • Alhambra ADU Guidelines


  • El Segundo ADU Guidelines


  • Cerritos ADU Guidelines


  • West Covina ADU Guidelines


  • Monterey Park ADU Guidelines


  • Baldwin Park ADU Guidelines


  • Lakewood City ADU Guidelines


  • San Dimas ADU Guidelines


  • Covina ADU Guidelines


  • Agoura Hills ADU Guidelines


  • Artesia ADU Guidelines


  • Bradbury ADU Guidelines


  • Claremont ADU Guidelines


  • Diamond Bar ADU Guidelines


  • Downey ADU Guidelines


  • Duarte ADU Guidelines


  • Glendora ADU Guidelines


  • Hermosa Beach ADU Guidelines


  • La Habra ADU Guidelines


  • La Puente ADU Guidelines



  • Lawndale ADU Guidelines


  • Monrovia ADU Guidelines


  • Rancho Palos Verdes ADU Guidelines


  • Rosemead ADU Guidelines


  • San Fernando ADU Guidelines


  • South Pasadena ADU Guidelines


  • Temple City ADU Guidelines


  • Walnut ADU Guidelines


  • Westlake Village ADU Guidelines


Hi, we're Paul and Jon - Co-Founders of GreatBuildz. We believe everyone deserves to find a great contractor, have a stress-free renovation, and enjoy their beautiful new space. There are so many contractors out there and it's often hard to tell the good from the bad... until it's too late. We started our company to help simplify your contractor search and help you have a stress-free renovation experience. We're always available to help, no matter where you are in the process. Click here to learn more about our story.

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