Depolluting facing for a building structure, e.g. a roofing membrane, including a first and a second layer. The first layer (3) acting as base for the at least second layer (2) wherein the second layer consist of granules (2) comprising NOx reducing anatase titanium dioxide. The first layer may constitute a bituminous membrane or a panel made up from plastic or metal. The granules may be fixed to the roofing membrane by pressing or calandering on the hot bituminous blend embedding the granules in the bituminous membrane. The granules can be made of anatase titanium dioxide and a mineral binder, for example silicate or phosphate.