ADU (Additional Dwelling Units)

New State laws took effect that create new opportunities for accessory dwelling units (also known as ADUs, “backyard homes,” or “granny flats”). 

Need more living space for your family? Want to earn rental income? You can build an accessory dwelling unit on the residential or agriculturally zoned property that you own.

What is an ADU?

An Accessory Dwelling Unit (ADU) is a residential unit that can be added to a lot with an existing single family home. ADUs can be detached (a separate building in​ ​a backyard), attached to or part of the primary residence, or a garage conversion.​ ​ADUs are independent rental units that have their own kitchens, bathrooms, living​ ​areas, and entrances.​ The ADU can be used as a rental, but cannot be sold separately from the primary or main single family residence. The existing residence must be a legally established structure.​

What is the law for ADUs in the City of Los Angeles?

The new state law (AB 2299) applies to LA and makes it easier
to build an ADU on a single family lot. The state law encourages the construction of accessory units because the City needs more housing. You can read the entire lawat the California Legislative Information website by searching California AB 2299.

​Contact your local building and safety department before hiring a contractor, each city may pass new laws that will affect ADU construction.

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Frequently Asked Questions

1. How much will my ADU cost?
Since the size and construction of each ADU will
differ, it is impossible to estimate the cost of your
ADU. The cost per-square-foot of an ADU is
likely to be the same as any other new residential
construction; builders and architects can give you
rough estimates.
2. How do I pay for my ADU?
There are a number of ways to pay for the
construction of an ADU. A common way is to
borrow from a home equity line of credit if you
have equity in your existing house. Other ways
can be more complicated: 1. You could refinance
your existing mortgage to take out a larger loan
to provide cash for ADU construction (this will
require equity in the home); 2. You may be able
to obtain a private construction loan to build
the ADU and refinance the loan with a new
mortgage when construction is complete. You
should start by talking to the bank that holds
your current mortgage.
3. How do I tell if I’m Near Transit?
Many lots in LA are within a half-mile of transit,
so that ADU parking will not be required. The
City publishes a transit map at
riding_metro/maps/images/system_map.pdf. First,
see if your lot appears to be within a half-mile
radius of a bus stop, rail station, or a dedicated
space where a shared-vehicle is parked. Second,
call the Dept. of Building and Safety to give your
property address. They can confirm whether you
need to provide parking for your ADU.
4. Can I Sell my ADU?
No, you can only sell your house and ADU
together. ADUs can be rental units or occupied
by the homeowner or family members.
5. Must the homeowner live on the property?
No, both the existing house and the ADU can be
rental units.
6. What if my current garage is in the front of my lot?
If your existing garage is at the front of your
house, in most cases you cannot convert it into
an ADU. You may be able to build an ADU
elsewhere on your property. You should check
with the Dept. of City Planning.
7. Can I legalize an unpermitted adu on my lot?
Although this guid focuses on new construction,
you may be able to get permits that will
legalize an existing rental unit on your property.

8. How big can I make my ADU?
There are some limits on the size of an ADU,
based on the size of your lot and existing house.
First, an attached ADU cannot be bigger than
50% of the existing house. For example, if your
existing house in 2,000 sq. ft., the attached ADU
cannot exceed 1,000 sq. ft. in size. Second, there
is a “mansionization ordinance” that usually restricts
the total square footage of all structures on
a lot to 45% of total lot size. For example, if your
lot is 10,000 sq. ft., the total built area (existing
house, ADU, garage, etc.) cannot exceed 4,500
sq. ft. In addition, most ADUs cannot exceed
1200 sq. ft. The Dept. of City Planning will need
to verify the specifics related to your project.
9. My lot seems too small or unusual. Can I still Build an ADU?
Almost every lot in LA is unique, so this guidebook
addresses the most common conditions.
There are various types of ADU that work on different
lots. For example, if a detached ADU will
not fit in your backyard, you might attach a new
unit to your current house. If the garage behind
your house is inconveniently located, you could
demolish and rebuild it with an ADU above.
Sketch your ideas as suggested in the guidebook,
and talk them over with the Dept. of Building
and Safety.

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