What you need to know about ADU’s

March 3, 2020

So, you’ve heard about ADUs, eh? Maybe a friend was talking about her ‘granny flat’, 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 additional living spaces on their property.

An ADU, otherwise known as an Accessory Dwelling Unit or Additional Dwelling Unit, is defined as a second structure 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 units in their backyard or converting their garage into a living space.

What you need to know about 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, have eased many previous restrictions to building these structures. To simplify this article, I’ll be discussing the guidelines specific to ADUs in Los Angeles, so please keep in mind that other local cities will likely have their own set of rules.

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 unit, as long as it’s near transit.

Increase in maximum permitted size

Greater variety of types of ADUs allowed
Some utility fees are being waived to encourage homeowners to build
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 is just a matter of submitting plans to the building department and going through the plancheck process to obtain a building permit.

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 of 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. But beyond that, 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 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 free-standing 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.

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.

It can be one or two stories, with a maximum height of 25’.
ADU above a garage, second story ADU Los Angeles

It must be in the backyard area and not in front of the existing home. A new detached accessory unit is limited to 1200sf, while an addition attached to an existing home is limited to the lesser of either 1200sf or 50% of the size of the existing home. A 400-600sf ADU is ideal for a one-bedroom floor plan and a 600-1200sf structure is enough to be one or two stories, with up to three bedrooms and multiple baths!

Los Angeles ADUs – What You Need To Know For 2020

Who can build an ADU?

The city of Los Angeles 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). 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).

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 5’ from both the rear and side property lines. A garage conversion into a living space, however, does NOT need to meet these setback requirements.

How much does an ADU cost?

An accessory dwelling unit 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 detached garage.
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 $50,000-$100,000 depending on the homeowner’s requirements. Costs to construct a new ADU can also vary considerably based on size, number of stories, location, access, etc, but will generally range from $100,000-$400,000.

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.

How long does it take to build an ADU?

As you can imagine, the timing is different for a garage conversion versus new construction project. For a garage conversion, you can expect the entire process to take 3-6 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 ADU 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.

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 plancheck and manage the process until a building permit is issued. Finally, construction can commence.

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

When looking to build an ADU or even start exploring 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.

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, don’t be afraid to address what you found with the contractor if there is anything concerning.

ADU Frequently Asked Questions

Q: Can I rent an ADU to a tenant?
A: Yes

Q: Can I sell an ADU without my house?
A: No

Q: Must I live on the property?
A: No, you can rent both the main house and the ADU.

Q: Can I legalize an unpermitted Accessory Dwelling Unit or garage conversion?
A: Yes, but you will need to bring it up to code and pay for the construction that is required. A good contractor can look at your property and give a rough estimate of the costs involved.

Q: Do I connect ADU utilities to the existing home?
A: Yes, or separate services can be added just for the ADU.

Q: If I have DWP power lines at the back of my property, where can I build an ADU?
A: A new ADU or garage conversion which is more than 10’ away from the edge of the powerlines is acceptable. An ADU within 10’ of the powerlines must file for a DWP encroachment permit (current processing time is 3-4 months). A garage that is currently under the powerlines may not be converted to an ADU.

Q: Do ADUs require pedestrian access?
A: Yes, a walking path access of 3’ wide is required from the front yard/sidewalk to the ADU (a driveway is acceptable).

Additional Resources:


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