Backyard Housing Boom: L.A. Sees Record Level of ADU Construction After Easing Restrictions

Los Angeles County has witnessed an unprecedented surge in the construction of Accessory Dwelling Units (ADUs), commonly known as "granny flats" or backyard cottages. In 2025, a record-breaking 10,230 ADUs were completed across the county. This figure marks a dramatic escalation from just 1,623 ADUs built in 2018, underscoring a transformative shift in the region's housing development landscape. The data, compiled by the University of Southern California's Lusk Center for Real Estate, reveals that ADUs constituted a substantial 37.5% of all newly certified housing units in 2025. This proportion is the highest recorded in the nearly ten years the Lusk Center has been tracking this specific metric, indicating ADUs are no longer a niche development but a significant contributor to the overall housing supply.

This boom in ADU construction arrives at a time when overall housing production in Los Angeles County saw a slight decrease, with 27,293 units completed in 2025, down from 28,498 in 2024. The continued growth of ADUs, therefore, becomes even more critical in addressing the broader housing deficit in Southern California. For years, the development of ADUs was severely hampered by a complex web of restrictive zoning laws, arduous permitting processes, and stringent limitations on development. Many local communities expressed reservations, citing potential increases in traffic congestion, parking shortages, heightened population density, and concerns about privacy and the subsequent impact on existing property values. These traditional objections created significant barriers for homeowners looking to add secondary units to their properties.

However, the regulatory environment underwent a significant transformation earlier in 2025 with the enactment of four new state laws. These legislative changes were designed to streamline ADU development by prohibiting local jurisdictions from imposing ADU rules that are more restrictive than state-level policies. This effectively removed many of the previously insurmountable hurdles that had discouraged and complicated the construction of additional dwellings on single-family lots. While these new laws have undoubtedly facilitated growth, the financial aspect of ADU construction remains a consideration. According to R&D Builders, a construction firm based in Woodland Hills, California, the cost of a basic garage conversion in Los Angeles, even without plumbing, can start around $25,000. A more complete conversion, which includes the addition of a bathroom and other essential amenities, would naturally incur higher costs, though specific figures for such comprehensive projects were not detailed. The increasing prevalence of ADUs offers a more incremental and often more accessible pathway to expanding housing stock compared to the traditional, large-scale new home construction projects.