Terrain is a contoured extension to a suburban home in Hitchin, Hertfordshire. This adaptative reuse project sees a parasitic extension form within the shell of a former double garage. The existing home is made up from former outbuildings of a country house, converted in 1980s the buildings are sporadic with multiple level changes and poor quality spaces. Our intervention sees the former garage stripped back, the front and side elevations kept and an infill new build timber extension emerge. The brick structure will be reused and adapted, the existing roof will be dismantled and reused in another Hyper_ Studio project continuing our work based on circular economy principles. The new build joins the former outbuildings and garage forming a cohesive home. Our intervention reinvigorates the homes plan reorienting the entrance and creating a grand hallway with sightlines to the vast garden beyond. The extension uses a sustainable mass timber structure, set out on a grid the columns allow the form to step, this contoured architectural aesthetic is clad with burnt larch timber on the roof and elevations. Four skylights are placed at the peak of each contour, orientated to the south they harvest light and channel through to the deep plan beyond. As the roof steps the interior exposes the timber structure creating a warmth and expressive form. The back façade steps in plan creating pockets for bench seating with vistas over the garden. This garden lounge wraps around a bespoke staircase. The bespoke staircase is formed around a integrated biofuel fireplace forming a modern ‘Inglenook’ around its base. The stair appears floating as it reaches up to the mezzanine. The space is define by a battened and louvred ‘filter’ with opening upper segments, designed to control the light.