Abstract: An overcladding structure for the roof of a building, to form a fresh roof overcladding the existing roof without needing to remove the existing roof and disrupting the inside use of the building, comprises fresh sheeting secured in position by anchoring to purlins of the existing roof. Short channel members are placed on the roof above and at intervals along the existing purlin and elongate Z section bearers are placed over these, and anchored by hook bolts to the existing purlins to strengthen the existing purlins. The fresh sheeting is bolted to the bearers and thermal insulating material may fill the space between existing roof and the fresh sheeting.