This is the first ever Accessory Dwelling Unit (ADU) built on a multi-family property in Mountain View,
CA. Though this was an early commision in our office, it underwent a 4-year journey from feasibility
to concept to construction, during which our office completed 6 other ADUs around California and
gaining a tremendous amount of experience with the typology. At the onset of the project, ADUs were
not permitted on multi-family properties but as the code progressed through the AB68 legislation
which eased these restrictions, the project was given a new life. Benefitting from the long permitting
and COVID-related delays, this ADU represents the culmination of the many strategies gathered
throughout our ADU experiences to create a design that is efficient, flexible, and cost-effective
without sacrificing thoughtful architectural design and meticulous details throughout.

Working within tight site constraints behind a large existing duplex, we employed fundamental
concepts of scale, proportion, and symmetry to create a compact footprint feel spacious and
grandiose. The plan is made of two 16’x16’ squares and is kept just under 500sf as a permitting
strategy to save on additional costs. The squares join at a central point that hinges between public
and private space. To the West is a living room and open kitchen that spills onto a private outdoor
dining patio and to the East is a bedroom, bathroom, and walk-in closet. Additional built-in storage
is tucked away throughout to maximize the efficiency of the floor plan. An axis that runs through the
center of the plan skewers both squares and plays with forced perspective to create an illusory sense of depth.

Sum of Squares ADU is one instance of a broader strategy for additional housing that can address
varying site conditions and client needs through its flexibility. As new legislation to address the housing crisis evolves through SB9 and efforts to upzone, we see this unique scenario of a duplex becoming 3-units (all of which are being rented) as an example of how an SB9-like idea can be realized by the typical homeowner.