Our original brief for this family was to extend an existing 250m2 house designed by architect Ted Levy in 1970. It was perched a storey above the road on a hillside. We proposed excavating back from the road under the house, to create a new entrance and forecourt at street level. Extending underneath as well as forwards on the upper floors would take the floor area to 400m2. This was the subject of a successful planning application in 2006. As financial circumstances improved for our Client we proposed a radical new approach; a scheme to demolish the house entirely and provide a new-build roughly to the footprint and volume established in 2006. By folding the house into a series of split-level floors following the natural gradient, we succeeded in increasing the floor area to 500m2. Significantly, the new brief allowed us to take a more holistic approach to the site and the family's ecological footprint. We gained a new planning consent which incorporated sustainable elements to achieve a Code for Sustainable Homes Level 4 and an Eco-homes rating of ‘Very Good’. The sustainable approach includes green roofs, rain-water harvesting and a full heat-recovery system. Passive techniques include solar-shading and a high thermal-mass exposed floor structure. The scheme is conceived as a highly-insulated and thermally massive ‘twisted/distorted’ box: the upper part is clad in kiln-fired larch (a first, at the time of the Planning consent, for this material on a UK residence) which sits atop a half-buried rendered base. Learning from Frank Lloyd Wright’s Falling Water, the house instinctively zig-zags up the hill, meeting the ground at different levels. A domestic staircase becomes dramatic as it winds up through a skylit central core, through the bedroom level and right up to the Master Bedroom suite. Symbolically this is placed above everything else, up at the former roof level, where a previously unseen view is revealed looking south over the rooftops of London.