Abstract: A beamless load bearing surface or stratum having a first group of polygonal plate members forming a peripheral ring. Each of such plate members forming such ring having a transverse edge supported on a longitudinal edge of the next adjacent plate member and so on around the ring. A second group of these plate members forms a second ring interiorly of the first ring. Each of the plate members in the second ring also having a transverse edge supported on a longitudinal edge of the next adjacent plate member of such second ring. In addition, each of the plate members in the second ring is supported along one of its longitudinal edges on the longitudinal edge of an adjacent one of the plates of the peripheral ring. Additional such rings inwardly of the second ring may be provided as desired as may also a central plate member for closing the opening left by the innermost such ring.