Junior ADU floor plans
A junior ADU is made inside your existing house, up to 500 sq ft in California, with its own entrance and an efficiency kitchen. These two layouts, a 450 sq ft studio and a 500 sq ft 1 bedroom, are measured and open in the editor.
500 sq ft junior ADU, 1 bedroom
| Kitchenette | 12'-10" x 8' |
|---|---|
| Bath | 6' x 8' |
| Laundry closet | 5' x 8' |
| Living | 14'-4" x 13' |
| Bedroom | 9'-6" x 13' |
$68K to $120K estimated build cost in Sacramento. Add your ZIP in the editor for your area.
More floor plans to start from
450 sq ft junior ADU studio
$64K to $114K estimated build cost in Sacramento. Add your ZIP in the editor for your area.
Junior ADU vs regular ADU
A junior ADU reuses space you already have, like a bedroom suite or part of an attached garage, so it's the cheapest way to add a unit. It can share a bathroom with the main house; these layouts give it its own.
The trade-off is size: 500 sq ft at most, and in most cases the owner must live in either the house or the junior unit.
California ADU size rules
- Detached ADU, largest
- Total floor area of a detached ADU can't exceed 1,200 sq ftGov. Code 66314(d)(5)
- What every city must allow
- A city can't use size, lot coverage or similar limits to block an ADU of at least 800 sq ft with 4 ft side and rear setbacksGov. Code 66321(b)(3)
- Attached ADU
- With an existing home, an attached ADU can't exceed 50 percent of the home's floor areaGov. Code 66314(d)(4)
- Junior ADU
- No more than 500 sq ft, inside the existing homeGov. Code 66333
Outside California, ADU size limits are set by each city or county. Your city's planning desk has the final word.
Will it fit your lot?
For homes in the California areas we cover, the free lot check reads your parcel, setbacks and local rules and shows the biggest unit that fits.
Check your lotQuestions
How big can a junior ADU be?
No more than 500 sq ft, inside the existing single-family home (Gov. Code 66333).
Does a junior ADU need a full kitchen?
No. It needs an efficiency kitchen: a sink, cooking appliance and counter space. The layouts here use a kitchenette.
Last checked 2026-11-02. Costs are estimates priced at ZIP 95818, not bids. Floor plans are concept layouts; a licensed designer or architect prepares the plans your city approves.