The present invention relates to an expandable polymeric composition that comprises: a) from 60% to 88% by weight of a vinyl aromatic polymer and/or copolymer, calculated respect to (a)+(b); b) from 12% to 40% by weight of a block copolymer, containing at least one vinyl aromatic polymer and/or copolymer and at least one hydrogenated diene polymer, calculated respect to (a)+(b); c) from 3 parts to 10 parts by weight of a blowing agent, calculated on 100 parts of (a)+(b).