CA AB3173

Requires cities and counties with populations exceeding 400,000 to permit microunit buildings in any zone where multifamily residential buildings are allowed, without requiring conditional use permits if not required for other residential units.

Allows microunit buildings to exceed standard density limits, building height by at least one story or 11 feet (whichever is greater), and floor-area ratios by up to 50 percent or to 3.5:1 (whichever is greater).

Eliminates parking requirements and private or common open space requirements for microunit buildings, while limiting setbacks to five feet minimum for residential portions and requiring none for ground-floor commercial uses.

Mandates that microunit buildings include onsite restricted affordable units at one of three minimum percentages: 8 percent for extremely low income, 11 percent for very low income, or 20 percent for lower income households.

Defines microunit buildings as structures with five or more microunits (habitable rooms without kitchens) and common kitchen and dining areas, with microunits comprising at least 75 percent of floor area and units limited to 25 percent.