Abstract: A sectional floating cover used to control vapor losses from storage tanks and other similar vessels containing volatile organic compounds, is disclosed. The floating cover comprises a plurality of buoyant steel chamber units secured together to form a continuous deck floating on the surface of the liquid in a storage tank. Each chamber unit includes an upper flat sheet, a corrugated lower sheet and sheet strips closing the ends of the corrugations. These parts are welded together in fluid-tight manner, so that the upwardly opening corrugations form independent fluid-tight cells. The units are easily assembled within the tank by simple bead connections readily accessible for crimping and resisting vertical shearing stresses.