A method of coating an expandable item (10) such as a pressure vessel or process vessel used for instance in the off shore oil industry. A compressible flexible intermediate layer (14) is provided on the item (10), and a support member (18) is embedded in the intermediate layer (14). The support member (18) comprises an open framework base (20) and a plurality of projecting members upstanding therefrom and extending out of the intermediate layer (14) away from the item (10). A thermally insulating coating layer (12) is applied over the intermediate layer (14) such that the projecting members (22) extend into the coating layer (12), and are wholly located in the coating layer (12).