Garage Conversion to ADU in Whittier: How It Works

California law lets you convert a garage into an ADU, and a city or county can't require you to build a replacement parking space when you do (Gov. Code 66314). That part is settled. The rest comes down to paperwork and the garage itself.

Before anyone draws plans, confirm which agency permits your property: the City of Whittier or Los Angeles County. A Whittier mailing address doesn't settle it. Look up your parcel first so the paperwork goes to the right office.

State law (Gov. Code 66317) requires a local agency to approve or deny a complete ADU application within 60 days. If the application is incomplete, the agency must tell you within 15 business days. Complete is the key word. A missing document means the clock hasn't started. A contractor who collects everything before filing saves you more time than one who files fast.

Stand in the garage with a notebook before anyone gives you a number. Where is the electrical panel? Is the water heater or a gas line in there? Where would a bathroom tie into existing plumbing? How does the floor meet the driveway at the old door opening? Those answers shape the scope. A conversion works inside walls that already exist, so it skips the new foundation a detached ADU needs. It still has to be built as a home: insulated, ventilated, and able to pass inspection as living space. If the garage was converted years ago without a permit, ask the permitting office how legalization works at your address before you demolish anything. Rentals must run longer than 30 days.

G3 General Contractors, Inc. is a licensed general contractor, CSLB #1145796. We build garage conversions, junior ADUs, free-standing ADUs and multi-unit ADUs, and we offer free estimates with no pressure. Call or text (714) 747-1912, Monday to Friday, 9 am to 5 pm. Have your address and a few photos of the garage ready, and we will set up a free estimate.