California Accessory Dwelling Unit (ADU) Rules

Everything you need to know about how to build a tiny home or granny flat in your backyard.


Zoning of Your Property

1. Single Family zoned property (Usually R-1 of a variation of this code can add an ADU.

2. Multifamily zoned property including Duplex or R2 cannot add an ADU today but will be able to if AB-68 passes which we expect will happen in September 2019.


Location of Property

1. Must be within ½ mile walking distance of public transit

2. Anywhere in California

3. Difficult if on steep hillside or street with limited fire access


Location of ADU

1. Anything inside your existing home can be segregated to become an ADU.

2. Remodel and stay within the footprint of an existing structure like a garage.

3. If AB-68 passes, you will be able to remove your existing garage and build a new structure on the same footprint limited to 16’ high. Will likely be able to expand footprint by up to 150 sq. ft. if expansion accommodates entry / exit.

4. A new structure in your backyard must be setback at least 5’ from the property boundaries. If AB-68 passes, this will change to 4’

5. No minimum space required between ADU and existing structure

6. In limited cases, may not be built in public utility easements if the easement specifically states no structure permitted (rare)

7. Will be more difficult if within 5’ of an electric pole as you will need utility approval


Do you live in Los Angeles? United Dwelling will transform your garage into an ADU at no cost to you!

Call for a free consultation: 310.393.5546


Size and Shape of ADU

1. Maximum size = 50% of your home size (rarely an issue)

2. If AB-68 passes, structures lower than 16’ are always allowed. Above 16’ (two stories) subject to discretion of permitting agency

3. As a practical matter, two stories always needs to be an entirely new structure due to setback rules and engineering limitations of original garage structures

4. Currently, there must be parking on the property for two vehicles. This limits conversions to homes with a large driveway. If AB-68 passes, parking that is removed to accommodate the ADU does NOT need to be replaced.


Construction Rules - Tradeoffs

1. Converting an existing separate structure;

a. Remodeling gives you a huge benefit on Title 24 which means reasonable rules about energy efficiency

b. BUT it means retrofitting the foundation to current standards which will cost about $20,000 to lift the old structure, replace the foundation and replace the old structure.

c. Perhaps keeping part of one wall will let you build new but call it remodel. Depends on your local department of building and safety.

2. Removing the old structure and replacing a new one

a. Is not feasible until AB-68 passes

b. Simplifies the foundation issue and makes for a safer, more energy efficient building

c. BUT runs into an impossible Title 24 issue for permits granted after December 31, 2019. On January 1, Title 24 requires new construction to be “Net Zero” meaning enough solar panels to generate all the power the unit needs. The problem is the roof of a 400 sq. ft ADU is too small to generate this much power and the cost would be too high relative to the value of the unit to justify.

d. AB 69 kind of addresses this but would not take effect until 2021

e. Simple solution is to define any ADU less than 800’ as an addition rather than new construction. Please email your state legislators to do this.

f. Making it larger than 400 sq. ft means you likely lose the benefit of AB 68 setbacks and have to move into the middle of your backyard


Do you live in Los Angeles? United Dwelling will transform your garage into an ADU at no cost to you!

Call for a free consultation: 310.393.5546