• We were asked to design a rear extension for this house on a sloping site and found that, as the garden was just a storey lower, we could provide a dining deck to the upper ground floor on top of the new guest suite at garden level, which is accessed via a generous spiral stair. • The differing cladding elements applied to the walls identify the separate blocks of accommodation. The stair, shower and bedroom volumes have vertical or horizontal larch cladding, mirror and render. This also serves to break the mass and refrain from overpowering the adjacent small garden. • We used low energy high thermal clay blocks for the walls and precaste floor beams for the floor and deck, to keep those elements as slim as possible, as they integrate the insulation requirements within their depth, to reduce the dig and increase the space generated. • For visual continuity from the kitchen dining area above, the spiral stair is in stained oak. The treads span between a central hollow steel post and the walls, and a flat steel handrail ribbons simply from the landing to the lower ground floor. • Serendipitously an excess order of blocks gave rise to the external floating larch stair design. • Painting the whole house and windows externally and resurfacing the front and side pathway and garden has upgraded it from a post war infill to a contemporary addition to the street.