Module 13 · Lesson 5
ADU + JADU: The Two-Unit Combo
California lets many single-family lots add BOTH a full ADU and a junior ADU. How the combo works, what JADUs require, and who it fits.
Module 1.2 planted the flag: many single-family properties can have both an ADU and a JADU. Time to cash that in — because for income-focused owners, the combo turns one house into a three-unit compound, ministerially.
The recipe. On a single-family lot, state law allows: the main house + one full ADU (detached, attached, or conversion — everything this course has covered) + one JADU (up to 500 SF, carved from within the existing house or attached garage). Three legal units, one lot, no rezoning, no hearings.
JADU rules, condensed (from 1.2 and 5.6, now operational): max 500 SF inside the existing single-family home's walls (attached garages count as "within"); its own exterior entrance; an efficiency kitchen (cooking appliance, food prep counter, storage — a full kitchen isn't required); may share a bathroom with the main house (though most owners give it one — a JADU sharing your bathroom is a roommate, not a unit); and the owner-occupancy string: someone on the deed generally must live on the property (in any of the three units). Recent law narrowed the requirement's reach (5.6), but plan around it: the combo is a strategy for owners who are staying.
Why bother? The JADU is astonishingly cheap per unit. You're converting existing bedrooms/garage space inside the house — commonly $40K–$80K — versus six figures for any full ADU. Stacked: house (you) + detached ADU (rent A) + JADU (rent B) turns the classic "ADU pays part of my mortgage" into "the property largely pays for itself." JADUs are also exempt from impact fees, and their utility connections ride the house's (no separate-meter drama — Module 7's simplest case).
The honest fit test: you live on-site indefinitely; your house has convertible space (a two-car attached garage or a wing of bedrooms you don't use); and you accept closer-quarters landlording — the JADU tenant shares your walls. Empty-nesters with big houses are the classic winners: the unused bedroom wing becomes income without touching the yard, and the yard still gets its full ADU.
Key takeaways
- Single-family lots can stack: main house + one full ADU + one JADU (≤500 SF, within the home or attached garage).
- JADUs are the cheapest unit in the book (~$40K–$80K) — existing interior space, efficiency kitchen, no impact fees.
- The string: owner-occupancy generally applies — this is a strategy for owners who are staying.
- Classic winner: empty-nesters converting an unused wing while the backyard gets the full ADU.