Abstract: Conversion of a ventilated roof to a thermally insulated, nonventilated roof without tearing off an existing roof sheathing which is, for example, made of asbestos cement and is carried by roof beams, includes the provision of holes in the old roof sheathing over the length of each roof beam at approximately equal intervals; and the provision of posts which are secured on the roof beams, extend through the holes, and project above the old roof sheathing. A heat-insulating intermediate structure is secured on the posts, has a U-shaped or hat-shaped profile, and extends over the posts which are arranged in a row, on which U-shaped or hat-shaped profile is secured the new roof sheathing. The space between the old and new roof sheathings is filled with an insulating layer.