Abstract: A cover for tank is formed from a plurality of panels attached together by cross members. The cover includes means for sealing the panels to the cross members, and means for sealing the panels and the cross members to the tank. The panels are constructed from a multiplicity of edge-to-edge planks. The planks may be connected together without welds, and the panels may be connected to the cross members without welds. The cover may be in the shape of an arch, or the shape of a dome. In another embodiment a dome-shaped cover may be formed from a plurality of panels each having the shape of a section of a circle. Each panel is connected between an adjacent pair of a plurality of radial members arranged in a radial pattern.