Abstract: A method of making a building panel comprises the steps of (i) casting a first or inner layer of reinforced concrete which has an obverse face and a smooth reverse face; casting a second or outer, ribbed layer of reinforced concrete which has an obverse face and a smooth reverse face; placing the first and second layers adjacent one another with the two obverse faces directed inwardly towards one another; and providing a layer of thermal insulation material between the two obverse faces. By this method a panel can be provided of which the faces are both smooth.