Spiral staircase, Pacific Palisades

This home in Pacific Palisades, California, is the personal residence of its designer, architect Michael Kovac. The scheme includes an external spiral staircase, a sculptural element that links the levels and gives structure to the rear elevation.

The treads and the associated decking are in Kebony Clear boards. The curved geometry calls for many cuts and closely spaced supports: the dimensional stability of the modified wood limits gaps opening between treads over time, on a piece where any movement would be immediately visible.

The photographs were taken seven years after installation. They show the silver-grey patina Kebony develops under prolonged sun exposure, with no finish and no maintenance beyond routine cleaning. The modified wood is produced by impregnating a certified softwood with a bio-based liquid, a process that permanently alters its cell structure.