BAY WATCH.

The spare design of a two-storey penthouse apartment takes advantage of the elevated site above a Californian beach at Marina del Rey and opens it up to the sky and sweeping views of the Pacific Ocean.

The apartment overlooks the beach at Marina del Rey, west of Los Angeles and beyond Santa Monica and Venice. Design began with stripping out 2400 sq ft, back to the essential structure and adapting the space to the flexible requirements of a young couple. The shell encompassed two levels including a roof terrace, and since the clients required a library, one was added to the terrace.

In contriving this airy light-filled dwelling, Lorcan O'Herlihy's starting points were the wide views and the nature of the long thin box with only one external wall. For the most part, division is informal with spaces flowing one into the other vertically and horizontally towards the light. Living quarters were installed downstairs with a generous open kitchen/dining area occupying the main central section raised to conceal ducting to services concentrated along the south wall. To the west you step down into the double-height living room where a glass curtain wall gives onto a terrace from which you can survey the beach. At the private east end is a spare room and elegantly detailed bathroom.

A flight of stairs, with slender balustrading, floats in front of a translucent glass wall, and takes you up to the galleried bedroom. One of the many nice details in this scheme is the catwalk which runs from it along the south wall, over the living room and through the glass wall to a perch -- a kind of crow's nest -- from which to watch the sun set over the Pacific. Such subtle reinforcement of the long axis is continued in the other direction in the form of a narrow wooden trellis tracing a path across the terrace from bedroom to library.

Light has been made an architectural element by means of skylights at intersections of wall and ceiling, and a light well over the stairs. In the shower room, a glass corner onto the terrace -- clear at the top, sandblasted and opaque at the bottom -- allows you the luxury of showering (in private) in sunshine.

Materials and finishes are few. In general, walls are white and reflective; warm maple floors in living room and bedroom are counterpoised to polished concrete ones used in the rest of the apartment; a bluestone washstand stands opposite a concrete bench in the main bathroom.

Such surfaces, austerely treated, emphasize volumetric simplicity; and, permeated by the diaphanous light characteristic of this part of the world, the sequence of flowing spaces becomes opulent.