ADU vs JADU
ADU vs JADU: size, location, and the owner-occupancy decision.
A JADU is a junior accessory dwelling unit — capped at 500 square feet and carved out of the existing primary home (or its attached garage). A standard ADU can be up to 1,200 square feet and built as a new detached structure. The differences run deeper than size: kitchen requirements, bathroom rules, owner-occupancy obligations, and parking replacement all diverge. Most California single-family lots are allowed one of each.
Option
ADU
Standard accessory dwelling unit
Typical cost
$80K–$400K+ all-in (CA 2026)
Option
JADU
Junior ADU — inside the primary home, ≤500 sq ft
Typical cost
$30K–$100K (San Jose, Redshed 2026)
Side-by-side comparison
| Attribute | ADU | JADU |
|---|---|---|
| Maximum size | Up to 1,200 sq ft in most CA cities | 500 sq ft hard cap — no expansion allowed (Redshed 2026) |
| Location | Detached, attached addition, or garage (attached or detached) | Inside existing primary home OR attached garage only — never detached |
| Kitchen | Full kitchen required | Efficiency kitchen only — sink, counter, cooking appliance, storage (no full gas range needed) |
| Bathroom | Must be private | Private OR shared with the primary home |
| Owner-occupancy (CA) | Not required for standard ADUs since 2020 | Required when bathroom is shared with main home (CA Gov Code 65852.22) |
| Parking replacement | Not required when within ½ mile transit or in existing structure | Required for attached-garage JADU conversions |
| Deed restriction | Many CA cities require — can't sell separately from main home | Required statewide — can't sell separately, recorded with the county |
| Rent range (Bay Area, Redshed 2026) | $1,800–$3,800/mo for one-bedroom | $1,400–$2,200/mo for studio/1BR |
| Combine with the other? | Yes — most CA single-family lots allow 1 standard ADU + 1 JADU | Same — one of each is the maximum on most lots |
Pick ADU when
- You want rental flexibility without owner-occupancy constraints.
- Your tenant will need privacy and won't share a bathroom with you.
- Your lot can fit a separate footprint with required setbacks.
- Your budget supports a full kitchen and bath build-out ($80K+ in California).
Pick JADU when
- Your budget is under $80K and you need a legal, rentable unit.
- You'll always live on the property — owner-occupancy is fine.
- You're housing a family member rather than a market tenant.
- You have usable inside space but no viable backyard for a detached unit.
- You want to do a JADU now and a standard ADU later when budget allows.
Want to run the math on your project?
Open the cost calculator with your inputs, or get matched with builders who can scope your specific lot.
FAQ
- Can I have both a JADU and a standard ADU?
- Yes — California law allows one standard ADU plus one JADU on most single-family lots. Convert an attached garage to a JADU and build a detached ADU in the backyard, and you have three legal residential units on a single-family lot. Combined Bay Area rental income on the two rentals can reach $4,500–$5,500/month (Redshed 2026).
- Does a JADU require owner-occupancy?
- Yes if the bathroom is shared with the primary home. Under California Government Code §65852.22, the owner must live in either the JADU or the main home in that case. Adding a private bathroom to the JADU changes the owner-occupancy landscape — confirm current local rules with your planning department.
- What's an 'efficiency kitchen' for a JADU?
- A food preparation counter, storage cabinets, and cooking facilities — but not a full range. A 240-volt induction cooktop, a countertop convection oven, and a compact sink satisfy California's JADU kitchen requirements. Budget $6,000–$14,000 for the kitchen, vs $15,000–$35,000 for a full ADU kitchen (Redshed 2026).
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