Situated in the Whitehall Park Conservation Area in North London, the existing two storey building with a flat roof is a former store and builders workshop. Built in 1936, it connected to the main house and occupied the end of its sloping garden. 
 
Within the existing footprint of the house, a new double height space for the stair connects ground and first floor. Leaving the existing park boundary wall untouched, a new generous window is cut into the brick wall above to give the bedroom a south facing aspect looking into the trees. A loft space under the new roof enjoys distant views across London. The roof pitch emphasises the changed aspect of the house and its improved relationship with the green space. A new spiral staircase connecting the top floor forms a half cylindrical brick tower, echoing the typical corner embellishment of the nearby terraces.