Liquefied gas storage installation comprising a load-bearing structure and a sealed and thermally insulating tank arranged in the load-bearing structure, the sealed and thermally insulating tank including a main structure made up of a plurality of tank walls connected to each other and fastened to the load-bearing structure, the main structure defining an internal storage space, the main structure comprising at least one sealing membrane (3, 13, 13') and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane (3, 13, 13') and the load-bearing structure; the sealing membrane (3, 13, 13'), the thermally insulating barrier of the main structure and a so-called upper load-bearing wall being locally interrupted so as to define a duct forming a load-bearing wall of a chimney extending along a vertical axis to an upper end consisting of a loading/unloading opening through which liquefied gas loading/unloading pipes can pass, said duct leading to said opening defining a liquid dome of the tank including, like the main structure of the tank (71, 71'), at least one sealing membrane (3, 33) and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane (3, 33) and the load-bearing wall; the liquid dome being situated at one axial end of the tank, a vertical wall of the main structure of the tank, referred to as the cofferdam wall, extends from said main structure to form, along the same plane, a wall (B') of the duct of the liquid dome; the sealing membrane (3, 13, 13', 33) of the main structure and the sealing membrane of the liquid dome are made up of a plurality of flat metal membranes, sealably fastened together, each having at least two perpendicular rows of corrugations (4, 5), the shape and dimensions of these two rows of corrugations (4, 5) being respectively identical for all of the membranes so that these juxtaposed membranes display a repeating pattern; characterized in that so-called adjacent membranes (13, 13') of the sealing membrane of the cofferdam wall of the main structure of the tank protrude at least partially into the liquid dome, said so-called adjacent membranes being directly sealably fastened to so-called adjacent membranes of the liquid dome. the sealed and thermally insulating tank including a main structure made up of a plurality of tank walls connected to each other and fastened to the load-bearing structure, the main structure defining an internal storage space, the main structure comprising at least one sealing membrane (3, 13, 13') and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane (3, 13, 13') and the load-bearing structure; the sealing membrane (3, 13, 13'), the thermally insulating barrier of the main structure and a so-called upper load-bearing wall being locally interrupted so as to define a duct forming a load-bearing wall of a chimney extending along a vertical axis to an upper end consisting of a loading/unloading opening through which liquefied gas loading/unloading pipes can pass, said duct leading to said opening defining a liquid dome of the tank including, like the main structure of the tank (71, 71'), at least one sealing membrane (3, 33) and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane (3, 33) and the load-bearing wall; the liquid dome being situated at one axial end of the tank, a vertical wall of the main structure of the tank, referred to as the cofferdam wall, extends from said main structure to form, along the same plane, a wall (B') of the duct of the liquid dome; the sealing membrane (3, 13, 13', 33) of the main structure and the sealing membrane of the liquid dome are made up of a plurality of flat metal membranes, sealably fastened together, each having at least two perpendicular rows of corrugations (4, 5), the shape and dimensions of these two rows of corrugations (4, 5) being respectively identical for all of the membranes so that these juxtaposed membranes display a repeating pattern; characterized in that so-called adjacent membranes (13, 13') of the sealing membrane of the cofferdam wall of the main structure of the tank protrude at least partially into the liquid dome, said so-called adjacent membranes being directly sealably fastened to so-called adjacent membranes of the liquid dome.