Detached ADU construction
Los Angeles.

A detached ADU is a ground-up build — same construction phases as a small house. Foundation, framing, roofing, plumbing, electrical, HVAC, fire sprinklers, insulation, drywall, finishes, landscaping, and exterior hardscape. Nothing is inherited from an existing structure, so everything is built to current code from the start.

California law allows detached ADUs up to 1,200 sq ft. Local cities cannot impose a size limit below the state minimum.

State law sets the baseline. Your city can be more permissive but cannot be more restrictive. Rear and side setbacks: 4 feet minimum from property lines for detached ADUs — cities cannot require more than 4 feet. Height: up to 16 feet for a single-story detached ADU, up to 18 feet if within half a mile of a major transit stop, and up to 25 feet for a two-story ADU on a multifamily lot or when attached to the primary dwelling (AB 1332). Lot coverage: state law prohibits cities from applying lot coverage or FAR limits that would prevent construction of an 800 sq ft ADU. Parking: no additional parking is required for ADUs in most circumstances — including when the property is near public transit, in a historic district, part of an existing structure, or when on-street parking permits are available. We verify all setback, height, and lot coverage requirements during the feasibility walk. Some properties have easements, utility corridors, or tree preservation zones that affect where the ADU can sit.

Detached ADU construction typically runs 18–26 weeks from contract to certificate of occupancy. Plan check for new-builds takes longer than conversions — budget 8 to 14 weeks for LADBS, shorter for some smaller cities.

Detached new-build ADUs in Los Angeles typically cost $200,000 to $400,000 depending on size, site conditions, and finish level. Per-square-foot costs range from $280 to $450. A one-bedroom unit in the 700 sq ft range on a flat lot usually lands around $220,000 to $280,000. Two-bedroom units at 1,000 to 1,200 sq ft run $300,000 to $400,000. Typical timeline: 18-26 weeks.

Setbacks, height limits, and impact-fee exemptions come from state law — your city cannot go more restrictive. Here is what matters in 2026:

Detached ADUs and custom pools have separate setback rules and can usually coexist. When you build both together, shared excavation, grading, and utility trenching typically saves 10–15% versus separate projects.

Detached ADU in Los Angeles, Ventura, and Orange counties.