#1 ADU Contractor in San Dimas
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Finding the right adu contractor in San Dimas means working with a team that understands both California’s evolving state law and the city-specific permit process your project will actually move through. The state codified its ADU rules in Government Code sections 66310 through 66342 in 2024, and the law was updated again on January 1, 2026. Under the current statute, square footage is calculated as interior livable space, a local agency 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.

In San Dimas, that application goes to the City of San Dimas Building and Safety Division, not a county counter. That distinction matters because Los Angeles County contains 88 incorporated cities, and the agency, the forms, and the staff all change from one city to the next even when the underlying state rules do not. The county’s own ADU ordinance, amended in July 2025, was later found non-compliant with state law by the California Department of Housing and Community Development in December 2025. Among other findings, it caps detached ADUs on a multifamily lot at two where state law allows up to eight. That ordinance covers unincorporated territory only, but it is a useful reminder that a local handout is not always current with the statute.

One detail specific to San Dimas is worth raising early in the planning process. Parts of the city sit inside specific plan areas that carry Early California and Western architectural guidelines, and exterior work in those areas runs through the design review process set out in Chapter 18.12 of the zoning code. Most of the residential tracts here were built after the city incorporated in 1960, following a history rooted in an 1887 railroad townsite and decades of orange growing. That era of construction means a lot of the housing stock consists of detached single-family homes on suburban foothill tract lots, which shapes where a new unit can physically sit and how far utilities will need to run.

The lot decides most of the practical questions. Roughly three-quarters of San Dimas housing is owner-occupied and laid out as detached homes rather than attached units, so we are frequently helping homeowners weigh a garage conversion against a new detached build in the rear yard. We walk every parcel before drawing anything, checking setbacks, grade, equipment clearance, and utility routes. That site review is how we figure out which option is realistic for your specific property rather than guessing from a satellite image.

Wherever your parcel sits, state law sets a floor that no local agency can go below. A city cannot cap an ADU below 850 square feet of interior livable space, or 1,000 square feet if the unit has 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 of an ADU 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. These protections exist statewide, and knowing them helps you push back if a local counter tells you otherwise.