House O, designed by Jun Igarashi, forgoes hallways and interior doors in favor of casually interconnected rooms.

Sleeping nooks that look like the grooves in a block of cheese.

A passage between the walls for hide and seek.

The addition’s two stories of cedar-framed sliding doors and window provide generous views of the house’s prized jacaranda tree. The addition’s polished concrete floor and white cladding extend into the garden, drawing occupants to the serene rear porch. There, they can relax on stools designed by Alvar Aalto and Charles Wilson while admiring the luscious greenery.

Situated on a sloped-site, each renovated space provides a unique perspective and vista to the dramatic natural surroundings. The office, with its stark modern furnishings and subtle artwork, allows the large window to serve as perhaps the most dramatic, singular frame to the foliage beyond.

A 24-by24-foot Cor-ten-clad pavilion tops the three-story addition.

This living/bedroom space showcases neutral tones and shades of white to contrast the continued use of natural, treated wood surfaces.