California ADU Permits Up Nearly Fourfold in Seven Years: About 9,000 in 2018 and Roughly 42,000 in 2025
Annual progress report data that California cities and counties file with the state Department of Housing and Community Development (HCD) show that permits for accessory dwelling units (ADUs) have risen every year since 2018: about 9,000 ADUs were permitted statewide in 2018, and roughly 42,000 in 2025, a nearly fourfold increase in seven years.
An ADU is a small, independent dwelling added on an existing residential lot, including backyard cottages and garage conversions, and state and local governments have promoted them as a way to add housing supply without developing new land. The steady rise in permits shows this housing type has grown from individual homeowners' experiments into a stable part of California's housing supply.
Owners report, however, that financing remains one of the main hurdles between a permit and a finished home, with construction loans and post-completion valuation affecting how quickly permitted ADUs get built. (Source: California Department of Housing and Community Development)
Source: California Department of Housing and Community Development
Published by GSM · USA (original Chinese edition)
Photo: 图片来源：Wikimedia Commons「EXTERIOR VIEW OF FRONT OF CLUB HOUSE. BOAT HOUSE AND DOCK TO THE RIGHT. PICTURE TAKEN FROM FRONT YARD OF COTTAGE 231, CAMERA FACING SOUTHWEST. SMALL WOOD FRAME SHED IN FRONT OF HABS ID,1-KU.V,1-I-1.tif」（Related names: Maul, David, transmitter 摄，Public domain），图中为后院附属住宅示意 Image: Wikimedia Commons "EXTERIOR VIEW OF FRONT OF CLUB HOUSE. BOAT HOUSE AND DOCK TO THE RIGHT. PICTURE TAKEN FROM FRONT YARD OF COTTAGE 231, CAMERA FACING SOUTHWEST. SMALL WOOD FRAME SHED IN FRONT OF HABS ID,1-KU.V,1-I-1.tif" (by Related names: Maul, David, transmitter, Public domain)
