This San Diego ADU project features the construction of three stacked accessory dwelling units (ADUs) in a multifamily (MDU) configuration, maximizing residential density on a difficult steep hillside lot. The design includes:

This hillside multifamily ADU build combines thoughtful design with strategic planning, tailored for challenging topography and tight code limitations.

The primary challenge of this San Diego MDU ADU project was overcoming vertical height restrictions on a steeply sloped lot while still complying with strict fire department access codes.

Under the City of San Diego’s ADU Bonus Program, the project aimed to increase density by adding multiple ADUs to the property. However, due to the sloped site, the building’s rear elevation exceeded 30 feet in height, which triggered compliance issues per Fire Plan Check Comment 00212.

Local fire code, specifically the California Fire Code (CFC) Section D105.1, requires aerial ladder access for structures over 30 feet. Unfortunately, the distance between the fire access road (Villa Street) and the rear of the structure exceeded the maximum ladder reach permitted. This created a serious life safety concern and posed a risk of permit denial if not addressed properly.

This design challenge reflects a common issue in steep-lot ADU development, where maximizing unit count and staying within fire code compliance can often conflict.

To solve the fire code challenge without sacrificing unit count or design goals, ADU Geeks implemented a smart roofline redesign using dormers.

After thorough collaboration with the city’s fire plan reviewer and analysis of 2022 CFC Section D105.1, the team determined that the roof structure could be strategically modified to meet code requirements. The solution: reconfigure the rear roofline with a dormer addition that would reduce the measured vertical height at the rear of the structure.

This brought the overall height within the 30-foot limit required for ground ladder access, resolving Comment 00212 and eliminating the need for:

This code-compliant dormer design allowed the project to move forward without delays or major infrastructure changes—proving that strategic architectural choices can overcome complex regulatory barriers in multifamily ADU construction.

The outcome of this hillside ADU project shows how smart design and early city collaboration can turn major constraints into successful outcomes. The project:

This case study reinforces the importance of fire code compliance, early planning, and thoughtful architectural solutions in San Diego ADU and MDU development—especially on difficult hillside lots.

If you're considering building an accessory dwelling unit on a sloped lot, or want to leverage the San Diego ADU Bonus Program, this project is proof that it can be done successfully with the right team.