The Copper Box is an architect-designed front extension to a 1930s semi in Moseley, Birmingham. Two builders had advised the clients to extend at the rear. The pre-design work concluded the opposite: the rear of the house already had decent light; the front rooms were the failure. The design works upward rather than outward, replacing the existing garage with a two-storey copper-clad volume on the same footprint, leaving the original brick bay and arched front door untouched. Copper chosen to weather honestly into the street, not imitate the host. The diagnosis was the work, not the drawing.