Abstract: Bitumen-impregnated cellulose fiber sheets include on one of their main surfaces, an adhesive primer layer, and, deposited on this adhesive primer layer, a fireproof coating including expandable graphite. In a preferred embodiment of the invention, the expandable graphite has a trigger temperature lower than 300° C. and the layer of expandable graphite corresponds to a dry matter basis weight of 80 to 140 g/m2. The sheets have a fire resistance fulfilling in particular the European Standard EN 13 501-5. They are mainly intended to be used as covering material, and in particular, as roof covering material.