#1 ADU Contractor in Alhambra
Custom Builds by Horizon Remodeling

Hiring an adu contractor in Alhambra means working inside a permit process that sits with the City of Alhambra Building Division, not the county, and understanding that distinction matters from the first day you consider adding a unit. California reorganized its ADU law into Government Code sections 66310 through 66342 in 2024, and changes effective January 1, 2026 shifted how square footage is counted to interior livable space only. Under that framework, the Building Division has 15 business days to determine whether your application is complete and 60 days to approve or deny it. Approval is ministerial, meaning no public hearing and no discretionary design review at the state level.

Alhambra adds a layer that matters here. The city applies single-family residential design guidelines and has adopted a historic preservation ordinance covering its older neighborhoods, so exterior changes to a pre-war Craftsman bungalow or a Spanish Colonial Revival house in areas like the Bean Tract or the Midwick Tract can draw design review on top of the standard building permit. That is a local requirement, not a state one, and it affects how we approach exterior materials, rooflines, and window placement on any detached or attached unit that faces a street or alley.

Los Angeles County has 88 incorporated cities, and the agency, the counter, and the applicable ordinance change from one to the next even where state rules are identical. The county’s own ADU ordinance, amended in July 2025 and later found non-compliant with state law by the California Department of Housing and Community Development in December 2025, governs only unincorporated territory. It does not apply to Alhambra, but it is a useful reminder that a local handout or online summary is not always current with the statute in effect.

The lot itself decides a great deal. Alhambra was built out largely in the 1920s, when the population grew from roughly 9,100 to nearly 29,500, and again through the 1940s. Most parcels carry a home on a raised foundation, and the original kitchen typically sits toward the rear of the floor plan. That layout shapes where a detached unit can land, how far utilities have to run, and whether a garage conversion or a new detached build makes more practical sense. We walk the parcel and assess setbacks, grade, equipment access, and utility routes before any drawing starts.

State law sets a floor that local agencies cannot go below regardless of where the parcel sits. A local agency cannot cap an ADU below 850 square feet of interior livable space, or below 1,000 square feet for a unit with more than one bedroom. Side and rear setbacks cannot exceed four feet. Owner-occupancy cannot be required as a condition of building an ADU. Construction cannot trigger a fire sprinkler retrofit of the main house. And there are no impact fees on a unit of 750 square feet or less. We help you understand how those protections apply to your specific parcel before the application is submitted.