Abstract: A method of applying a laminate (4, 5, 6) to one side of a wall of a storage vessel (1) and which comprises: securing a first substantially impermeable layer (4) to said one side of the wall; securing an intermediate liquid pervious layer (5) to the exposed side of said first layer (4); and, securing a second substantially impermeable layer (6) to the exposed side of the intermediate layer (5) so as to define a fluid receiving space between the first and second layers (4, 6) in which a monitoring fluid can be received to permit monitoring of the sealing integrity of the storage vessel. The intermediate layer (5) includes a liquid or fluid pervious layer (5a) e.g. of open celled foam, which is bonded to the first impermeable layer (4) and a semi-impermeable layer (5b) e.g. of paper which faces and which becomes bonded to the second impermeable layer (6) upon at least partial impregnation by the material of the layer (6).