Abstract: Intumescent composition comprising: A) a binder comprising (i) a resin comprising a polysiloxane chain or a precursor for said chain, (ii) optionally an organic resin, and (iii) at least one type of functional group selected from the group consisting of epoxy, amine, mercaptan, carboxylic acid, acryloyl, isocyanate, alkoxysilyl, and anhydride groups, said functional groups being present as pendant and/or terminal groups on said resin comprising a polysiloxane chain or the precursor for said chain, and/or on the organic resin, provided that if the binder contains alkoxysilyl groups as the only type of said functional groups, these alkoxysilyl groups are present on the organic resin, B) a compound capable of reacting with or catalysing the reaction between the functional groups, and C) a spumific and a char forming adjunct.