When you climb up the vertiginous zig zag of Blue Pool Road you almost miss the way the elevation of the building up there on your left almost out of sight has been nudged apart to reveal a whole vertical section of the façades ripped out and the gap stuffed with three giant elongated ice cubes which seem, when you toil up the hill a bit, to be falling into the swimming pool in an elegantly detailed podium.What is further intriguing is that, unlike the surrounding concrete apartment buildings, the façades on either side of the tumbling ice cubes seem to be made of commercial office-style curtain walling but given the location in an upmarket residential part of Hong Kong this can't be anything but a house. Clearly it's for a rather special client.Ken Wai recounts that over a meal his client said he wanted to house his extensive art collection, himself and his wife, their son and his family and guests.And with a prudent eye to the distant future, a special requirement was that the house should be readily convertible into apartments.Wai points to the discipline and regularity behind the building's makeup which, he says, 'lends the building a dignified expression'. It is this orderliness which makes the tumbling of the staircase enclosure more transgressive. It is expressive not only of falling water but of the idea of evanescence, collapsing elements, the building as shambles. Wai puts it thus, 'Juxtaposed against this regimented exterior a sensuous free form staircase has been inserted and collided into the formal frontage.'Wai, cites as one of his concept sources an old photograph showing a waterfall dropping through a background formation of stacked basalt organ pipes – and an even older lithograph of a similar waterfall somewhere on 19th century Hong Kong Island. In all three backgrounds including the one before us is archetypal nature: trees, scrub and rock.The glass used on all the façades is low iron. Low-E openable double glazing with a sun shading layer between the inner and outer panes of glass. The tumbling staircase glass, made in China, which is curved and bent right to the limits of the structure of the glass, has a printed fritted interlayer. This also gives the glass of the ice cubes a different shimmer a consequence of the different quality of reflectivity. As with the main façade glass this regulates the amount of solar light and heat entering the rooms. It is a balance between privacy, temperature control and glare. Where privacy is an issue the glazing units have timber strips which diffuse light and stop outsiders from seeing in.