What it is
A junior ADU (JADU) is a small unit carved out of an existing house, such as a bedroom or an attached garage converted into a studio with an efficiency kitchen.
The rules
- No more than 500 square feet, contained entirely within a single-family home; it can't be in a separate structure (Government Code § 66313(d)).
- An attached garage counts as part of the home for a JADU (§ 66333(d)).
- It may have its own bathroom or share the house's. If it shares, the owner must live in the house or the JADU (§ 66333(b)).
- It can't be a short-term rental: rentals must be longer than 30 days (§ 66333(g)).
Summarized from the state's ADU Handbook (HCD). Local rules add details; check with your city before designing.
By the numbers in Los Angeles
The City of Los Angeles issued 710 permits for junior ADUs in 2025, 10% of all its ADU permits. That share was 4% in 2020. Of the four ADU types in 2025, junior ADUs were the least common, the fastest to permit and the lowest in declared value. Permits issued in 2025 took a median of 72 days from application (the middle half took 37–141 days). From permit to the city's final sign-off took a median of about 11 months, and 83% of permits issued from 2020 through 2023 have been signed off as finished. Owners declared a median of $35,000 on permits issued in 2025 (middle half $21,500–$55,000). Declared values understate the full cost.
| Year | Junior ADU (JADU) permits | Share of ADU permits | Median days to permit | Median declared value |
|---|---|---|---|---|
| 2020 | 137 | 4% | 94 | $20,000 |
| 2021 | 324 | 6% | 132 | $25,000 |
| 2022 | 488 | 7% | 110 | $35,000 |
| 2023 | 570 | 9% | 71 | $30,000 |
| 2024 | 662 | 10% | 68 | $30,000 |
| 2025 | 710 | 10% | 72 | $35,000 |
Where in the San Fernando Valley
The Valley neighborhoods with the most junior ADUs (2020 to date) are Northridge (227), Woodland Hills (219) and Reseda (217). As a share of each neighborhood's ADU permits, they are most common in Northridge (18%), Woodland Hills (17%) and West Hills (16%).
Practical tips
- Decide early between a shared or separate bathroom: it drives cost and the owner-occupancy rule.
- A JADU needs its own exterior entrance; check where one can go.
- Because it stays inside the house, a JADU usually needs no new foundation or separate utility runs.
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