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 R13Si(OSiR22)x(OSiMeH)yOSiR13, where each R2 is independently selected from saturated hydrocarbon radicals comprising from 1 to 10 carbon atoms or aromatic hydrocarbon radicals and each R1 is independently selected from hydrogen or R2, x is zero or an integer and y is an integer. The organohydrogensiloxane has at least three Si—H bonds per molecule.