Reusable system for constructing a temporary building or tent, comprising a plurality of beams (3; 30), a separate coupling part (3', 3"), an upright, at least two skirtings (5, 5'; 50), a side wall, and a floor panel (12; 120, 121); wherein: said beams extending parallel in a first direction and each connected fixedly at an end thereof, for instance in integral manner, to a respective separate coupling part (3', 3"), wherein the coupling part of a beam is provided on an upper side with first and second coupling means and further comprises a support element for supporting said upright placed on the coupling part; said skirtings being each provided on an underside thereof with third and fourth coupling means placed on opposite sides of the skirting, wherein the skirtings are each provided on the underside with a recess on either side of the skirting for partially flush placing of the skirting between a pair of adjacent beams, and wherein each skirting is placed perpendicular to the first direction on an upper side of said pair of adjacent beams and extending vertically therefrom by coupling between the first coupling means of the coupling part of one beam of said pair of adjacent beams and the third coupling means of the skirting and by coupling between the second coupling means of the coupling part of the other beam of said pair of adjacent beams and the fourth coupling means of the skirting, wherein each skirting comprises on an upper side thereof a profiling for coupling to said side wall of the system that extends between uprights placed on the upright supports; said floor panel extending between said pair of adjacent beams in a direction perpendicular to the first direction and resting thereon, wherein the floor panel is provided on an underside, at least at the position of the beams, with a thermally insulating spacer for preventing a cold bridge between floor panel and beam; wherein the floor panel is provided on a side facing toward the beams with a recess for partially flush placing of the floor panel between the pair of adjacent beams; characterized in that the floor panel is partially located above the upper sides of the beams and supported thereby. said beams extending parallel in a first direction and each connected fixedly at an end thereof, for instance in integral manner, to a respective separate coupling part (3', 3"), wherein the coupling part of a beam is provided on an upper side with first and second coupling means and further comprises a support element for supporting said upright placed on the coupling part; said skirtings being each provided on an underside thereof with third and fourth coupling means placed on opposite sides of the skirting, wherein the skirtings are each provided on the underside with a recess on either side of the skirting for partially flush placing of the skirting between a pair of adjacent beams, and wherein each skirting is placed perpendicular to the first direction on an upper side of said pair of adjacent beams and extending vertically therefrom by coupling between the first coupling means of the coupling part of one beam of said pair of adjacent beams and the third coupling means of the skirting and by coupling between the second coupling means of the coupling part of the other beam of said pair of adjacent beams and the fourth coupling means of the skirting, wherein each skirting comprises on an upper side thereof a profiling for coupling to said side wall of the system that extends between uprights placed on the upright supports; said floor panel extending between said pair of adjacent beams in a direction perpendicular to the first direction and resting thereon, wherein the floor panel is provided on an underside, at least at the position of the beams, with a thermally insulating spacer for preventing a cold bridge between floor panel and beam; wherein the floor panel is provided on a side facing toward the beams with a recess for partially flush placing of the floor panel between the pair of adjacent beams; characterized in that the floor panel is partially located above the upper sides of the beams and supported thereby.