British contractors are now using polystyrene sheets as formwork lining for exposed site-cast concrete. The practice has been adopted on two counts: one, the high gloss of the sheet gives a surface finish to the concrete which is exceptionally smooth and entirely blemish-free; and two, the lack of adhesion of polystyrene to concrete dispenses with the need for form oil. The lining material is shaped by moderate controlled heating and glued in position. Sheets are .06 inch thick.