The most common question we get is some version of "how many ADUs can I build on my house." For a single-family lot in California the state answer is two units: one ADU and one JADU. Cities cannot reduce that number.
The combination the state guarantees
- One detached ADU of up to 800 square feet, 16 to 18 feet tall, with four-foot side and rear setbacks. Many cities allow 1,000 to 1,200 square feet.
- One JADU of up to 500 square feet inside the existing home or attached garage.
- Alternatively, one converted ADU (garage, basement, or other accessory structure) plus one JADU, or one converted ADU plus one new detached ADU of 800 square feet.
These are approved ministerially within 60 days. No hearing, no neighbor notice, no design review beyond objective standards.
What a city cannot do
A local ordinance cannot require owner-occupancy for the ADU (AB 976), cannot require replacement parking when a garage is converted, cannot require any parking within a half mile of major transit (AB 2097), cannot apply a minimum lot size, and cannot impose lot coverage or floor area limits that would prevent the 800 square foot unit. Impact fees are waived for units under 750 square feet. If an ordinance tries any of this, the state law controls and, since 2025, HCD can void the ordinance.
The numbers on a typical lot
Take a 6,000 square foot lot in the San Fernando Valley with a 1,400 square foot house and a detached two-car garage. Convert the garage to a 400 square foot ADU, carve a 450 square foot JADU out of the house, and the lot goes from one unit to three. Typical 2026 cost: roughly $120,000 for the garage conversion and $90,000 for the JADU. Combined rent: around $4,000 a month. Because the lot stays under four units, value is measured on sales comps, and a three-unit property in that market commonly appraises $250,000 to $400,000 above the single-family comp.
Multifamily lots are different
If your lot already has two or more units, the two-ADU rule does not apply; SB 1211 does, and the cap rises to eight detached units plus converted-space ADUs.
Check your lot
Parcy identifies whether your parcel is single-family or multifamily, applies the right rule, draws the buildable area, and places the units. Download Parcy and enter the address.
Frequently asked questions
How many ADUs can I build on a single-family lot in California?
One ADU and one JADU, approved by right. A converted ADU plus a new detached ADU is also allowed in some combinations.
Can the city require parking for my ADU?
Not within a half mile of major transit, not for a converted garage, and not more than one space per unit elsewhere.
Informational only. Not legal, architectural, or investment advice. Confirm current rules with your local planning department.