ADU Construction in Millbrae — Where Higher Property Values Justify a Higher Standard of Construction

Millbrae’s flatland neighborhoods sit east of El Camino Real, close to downtown Broadway, BART, and Caltrain. Meadow Glen is one of Millbrae’s first post-war suburbs — compact, well-kept homes from the late 1940s and 1950s, walking distance to downtown, with a walk score of 91. Bayside Manor and Marino Vista Park are on the eastern side, closer to Highway 101 and SFO, with some of Millbrae’s most affordable homes — smaller properties under 1,000 square feet on smaller lots.

The compact homes in these neighborhoods often have single-car garages that can be converted to studio or one-bedroom ADUs. The proximity to the BART/Caltrain station means ADUs within half a mile qualify for the parking exemption — no dedicated parking space required. This is a significant advantage on smaller lots where sacrificing a parking space would be impractical.

Where rear-yard depth allows (25+ feet behind the house after setbacks), a small detached ADU can work on these lots. The flat terrain keeps foundation costs lower than the hillside neighborhoods.

Millbrae Highlands is one of the city’s original subdivisions, dating to 1927, with tree-lined streets and a mix of pre-war and post-war home styles — many are larger two-story homes within walking distance of downtown and the intermodal station. Capuchino and Mosswood sit at the transition between flatland and foothills, with post-war homes on lots that start to show some grade change.

ADU opportunities in these neighborhoods include both garage conversions and detached rear-yard units. The lots tend to be larger than the downtown flatlands, providing more flexibility for detached ADUs. The Highlands’ mature landscaping introduces a Millbrae-specific consideration: tree protection (covered in the permitting section below).

Millbrae Meadows is the city’s pristine mid-century neighborhood — built from the 1950s through the 1970s on the western hillside behind Capuchino, with median home values around $2.4 million. Mills Estate is the high-end neighborhood at Millbrae’s southern border with Burlingame, featuring larger contemporary and mid-century homes with bay views. Green Hills and Telescope Hills are similar premium hillside neighborhoods.

These larger hillside lots often have the square footage for a substantial detached ADU — two bedrooms, 800 to 1,000+ square feet — with natural separation from the main house created by the slope. The hillside terrain means engineered foundations, retaining walls, and drainage systems, but the property values and rental rates justify the investment.

Many of the mid-century and raised ranch homes in these neighborhoods have lower-level space — garages, utility rooms, unfinished areas — at grade or partially below grade on the uphill side. Converting this space follows the same approach as the raised ranch conversions in San Bruno’s hillside neighborhoods: moisture management, fire-rated separation, adequate ceiling height, and natural light.

At $2+ million property values, the ADU in these neighborhoods needs to be built to a finish level that matches the main house and the neighborhood. This means quality materials, thoughtful design that complements the architecture, and construction detailing that performs long-term — not a prefab unit dropped into the backyard.