Membrane body (1) comprising at least one pair of panels (10, 11) connected together in an adhesive manner and for each pair of said panels (10, 11), at least one flexible sheath (15) arranged stably according to a set pattern to resist membrane stress acting on the panels (10, 11); each sheath (15) housing a respective tie rod (16), connected to the panels (10, 11) in an end position in a set manner in such a way as to be suitable for resisting normal stress to free the panels (10, 11) from the respective membrane stress, thereby maintaining the group of the panels (10, 11) flexible and maintaining the corresponding production method.