I want to build an ADU, what do I need to do?

An ADU is a secondary housing unit on a residential lot with a primary home. It's also called a:

• Guest house

• Granny flat

• In-law suite

• Casita

• Backyard home

✅ Key Features:

• Detached (separate building)

• Attached (added onto the main house)

• Garage conversion or basement unit

• Has its own kitchen, bathroom, and entrance

• Up to 1,200 sq ft (or more, depending on the city and lot size)

Common Uses:

• Rental income

• Housing for family or caregivers

• Multigenerational living

A JADU is a smaller, more limited type of ADU created within the walls of the existing home—usually converting a bedroom or part of the home.

✅ Key Features:

• Maximum 500 sq ft

• Must be located inside the main residence

• Can share a bathroom with the main home

• Small “efficiency” kitchen required (no oven/stove—just sink, fridge, and cooktop)

• Owner must live on the property (in either the main house or the JADU)

• Often cheaper and faster to build than a full ADU

Feature	ADU (Accessory Dwelling Unit)	JADU (Junior ADU)
Size	Up to 1,200 sq ft (800 sq ft must be allowed by cities)	Max 500 sq ft
Location	Detached, attached, garage or basement conversion	Must be within the main home
Kitchen	Full kitchen (stove, fridge, sink, cabinets)	Efficiency kitchen (no stove/oven)
Bathroom	Private and separate required	May share bathroom with main house
Entry	Separate exterior entrance required	Separate entrance also required
Parking	Often waived if near transit or converting an existing space	Same parking rules as ADU
Owner Occupancy	Not required (per 2023 CA law)	Required — owner must live on site
Rental Use	Allowed for long-term rental	Allowed for long-term rental
Cost to Build	💰💰💰 Higher construction costs	💰 Lower-cost retrofit
Permit Timeline	60-day state-mandated approval	Same 60-day timeline as ADU

Practical Steps

• Check your zoning: Verify your parcel is zoned for duplex + ADU.

• Contact your planning department: Clarify local parking, height, and permitting nuances.

• Engage an architect or ADU specialist: They’ll help with both conversion and detached ADU design.

• Follow state size limits: Usually up to 1,200 sq ft each (attached/detached) and obey setback and height rules.

• Apply permits: ADU permits are ministerial—meaning expedited, no discretionary hearings.

WANT MORE INFORMATION TRY THIS ADU CALCULATOR FOR BUDGET AND ROUGH COSTS

WANT TO DO AN ADU ON YOUR PROPRETY? CALL US TODAY WE CAN DO ALL THE WORK FOR YOU 310-801-0633 Willie Baronet