An intumescent coating material, the material comprising first and second parts mixable together so that the material will cure by an addition reaction in the presence of a metallic catalyst. The first part including a polydiorganosiloxane polymer having at least two unsaturated groups per molecule. The first part also including the metallic catalyst and a reinforcing filler. The second part including an organohydrogensiloxane crosslinker described by formula R 1 3 Si(OSiR 2 2 )x(OSiMeH) y OSiR 1 3 , where each R 2 is independently selected from saturated hydrocarbon radicals comprising from 1 to 10 carbon atoms or aromatic hydrocarbon radicals and each R 1 is independently selected from hydrogen or R 2 , x is zero or an integer and y is an integer. The organohydrogensiloxane has at least three Si-H bonds per molecule.