This invention relates to a lightweight housing module comprising at least one stretched fabric intended to form the roof of said module and fixed along its lower edge on a rigid frame maintained at a distance from the ground by a plurality of lateral posts, remarkable in that it comprises vertical panels and/or opening frames in order to close in a substantially sealed manner its vertical facades and a false ceiling arranged in order to be arranged under said fabric inside said lightweight housing module and fixed to the frame. This invention also relates to a modular building remarkable in that it comprises a plurality of lightweight housing modules, according to the invention, arranged next to one another, and a system for sealing between the adjacent lightweight housing modules. This invention also relates to their method of assembly.