System-floor substructure for stand building, comprising a number of bearing sections which, in combination, define a grid having rectangular compartments. The floor further comprises a number of bearing feet which are detachably connected to the grid. The bearing sections each comprise two upright sidewalls extending in the longitudinal direction of the bearing section and a top wall interconnecting the upright sidewalls. Each bearing foot comprises a horizontal bearing face and four upright members mounted on top of the bearing face and, in combination, defining the corner points of a quadrangle. The smallest distance between parts of adjacent members of a bearing foot at least substantially corresponds to the distance between the outer sides of the upright sidewalls of a bearing section. At least three of the four members have each such dimensions that they can be received between the inner sides of two upright sidewalls of the bearing sections with an at least substantially proper fit. Depending on the position of the bearing foot, a bearing section is received in the floor between adjacent members of a bearing foot or a member of a bearing foot is received between upright sidewalls of a bearing section.