SM20 is an accessory dwelling unit (ADU) located at the rear of a single-family home in Santa Monica, California. The new one-bedroom apartment is built above an existing two car garage. The shape of its roof was conceived to maximize the area available to install solar panels and screen the mechanical equipment. The exterior steel stair is screened with louvers to provide privacy and an independent access to the new residence via an outdoor patio. The interior space features a soaring cathedral ceiling in the living area and a sliding wall that opens to connect all the rooms and provide flexibility of use. The façade has a modern flair with custom details featuring concealed gutters and fiber cement board cladding.