ADU Guide: Building an Accessory Dwelling Unit in Alhambra

State law vs local rules

California Government Code 65852.2 (the state ADU law) sets a floor: every single family lot can have at least one ADU plus one Junior ADU. Cities can add layers on top but cannot block ADUs entirely. Alhambra has its own ordinance that further shapes setbacks, height, and lot coverage.

Site feasibility

Before design, walk the lot for setbacks, sewer capacity, electrical service capacity, slope, and easement constraints. Detached new build ADUs need a footprint and yard space. Garage conversions reuse an existing structure. Junior ADUs sit inside the main house. Each path has its own cost basis and construction timeline.

Permits in {city}

ADU submittals are ministerial in California, meaning the city reviews them administratively without discretionary review. City of Alhambra Community Development Dept, 111 S First St. Building Division 626-570-5032. Code: Alhambra Municipal Code Title 20. typically completes plan check in 60 to 120 days. ADUs may not be prohibited on landmarked or registered properties, but they must conform to the ADU regulations and the Historic Preservation Ordinance. No additional parking required if the parcel is on a register. Garage conversions usually clear faster than detached new builds.

Construction window

Site clearance, foundation, framing, MEP rough, exterior dry in, interior finish, fixture install, final inspection. ADU builds in Alhambra typically run 4 to 7 months of construction. From signed design contract to final inspection most projects total 8 to 14 months.