ADU guide

Garage to ADU: how it differs from a basic conversion

People use "garage conversion" and "ADU" interchangeably, but they are not the same project. Understanding the difference early saves money, time, and disappointment.

The core difference

A basic garage conversion turns the garage into more of your existing home — a room such as an office, den, or bedroom that shares the home's systems. An ADU (accessory dwelling unit) is a legally independent home: it has its own kitchen, its own bathroom, its own entrance, and it can be lived in separately.

	Basic conversion	ADU
Kitchen	Optional / none	Required (full kitchen)
Bathroom	Optional	Required (full bath)
Separate entrance	Not required	Typically required
Utilities	Shares the home's	Often independent metering/service
Permitting	Standard remodel permits	Distinct ADU approval process
Can be rented	Depends on local rules	Yes, where permitted
Relative cost	Lower	Higher

Why an ADU costs more

Everything that makes a unit independent adds work: plumbing for a kitchen and bath, dedicated electrical, insulation and finishes to residential standards, egress, and often utility upgrades. See the breakdown in our cost guide.

General information vs. local legal requirements

California has statewide ADU laws that interact with local ordinances. Start with our California guide for context, then verify specifics for your city.

Is your garage an ADU candidate?

Detached garages, ceiling height, existing utilities, and lot conditions all matter. The assessment flags the factors most likely to affect an ADU conversion and gives you a list to investigate.