Portal House is a light-filled three-storey family home overlooking Balmoral Beach to North Head. The portal frame structural system was chosen for its ease of replication across a consistent grid on this steep site. This creates open bays between the frames, allowing light to penetrate the full length and depth of the basement level on both northern and southern flanks. The east–west orientation is optimised with a recessed middle floor level: the top floor overhangs to form eaves that shield against summer sun while admitting full winter light. Concrete grounds the form, copper warms it and glazing pulls in the coastal outlook.