#1 ADU Contractor in San Marino
Custom Builds by Horizon Remodeling

Finding the right adu contractor in San Marino means understanding that this city operates under a distinct set of rules that shape every phase of an accessory dwelling unit project, from the first site visit to the final inspection. California consolidated its ADU statutes into Government Code sections 66310 through 66342 in 2024, and those rules were updated again on January 1, 2026. Under the current framework, square footage is counted as interior livable space, the reviewing agency has 15 business days to determine whether a submitted application is complete, and then 60 days to approve or deny it. Approval is ministerial, meaning no public hearing is required and no discretionary design review can be layered on top of the state process.

Every application for a property in San Marino goes to the City of San Marino Building and Safety Division. That agency handles its own counter and its own review, separate from Los Angeles County, which governs unincorporated territory rather than the incorporated cities. That distinction matters because the county’s own ADU ordinance, amended in July 2025, was 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. A city property is not governed by that ordinance, but the episode is a useful reminder that local handouts are not always current with the statute.

State law sets a floor that no local agency can go below. A city cannot restrict an ADU to less than 850 square feet of interior livable space, or less than 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 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.

The lot itself drives most of the remaining decisions. San Marino’s housing stock is overwhelmingly prewar, with the majority of homes built between 1920 and 1950 on generous parcels, many averaging over 30,000 square feet. Those older floor plans are formal and compartmented, with the kitchen set apart from the main living rooms as was standard practice when these homes were designed. That layout and that lot size shape where a detached unit can reasonably sit, how far utility lines have to run, and whether a garage conversion or a purpose-built detached structure makes more practical sense for a given property.

One local factor carries real weight here. The city applies strict design review and zoning standards to protect its residential character, so exterior changes draw closer scrutiny than they typically do in neighboring cities. We walk every parcel before drawing anything, checking setbacks, grade changes, equipment clearances, and utility routing, so that what we submit to the Building and Safety Division reflects the actual conditions on the ground and moves through review as efficiently as the process allows.