Abstract: The invention comprises a liquid storage tank having a floating roof of the type in which the roof rises and falls with changes in the level of the liquid and a seal provided between the edge of the roof and the inner wall of the tank to prevent contamination or evaporation of the liquid and to allow for any out of truth of the tank and any lateral movement of the roof having the seal supported between a side wall of the roof and the tank wall in the form of a continuous annular bag of rubber or plastics coated fabric comprising inner and outer chambers the inner chamber lying in contact with the side wall of the floating roof and containing a liquid and the outer chamber lying in contact with the tank wall and containing a pre-shaped pad of a synthetic foam material, the whole being supported from the roof by bolts which pass through the top edge of the seal bag.