Abstract: A beam of the type used in the building industry comprising a top and bottom plate (1, 2) secured in a fixed spaced relationship from each other by corrugated sheet metal (3); the metal (3) being dispersed such that its planar surfaces span the distance between the top and bottom plates (1, 2) with the corrugations configured substantially as a rectangular wave having surfaces (4) parallel to the longitudinal axis of the plates and additionally surfaces (8) substantially transverse to such axis; the arrangement being such that the substantially transverse surfaces (8) act as spacers between the top and bottom plates (1, 2) whereas the surfaces (4) of the corrugated metal (3) lying parallel to the longitudinal axis of the top and bottom plates (1, 2) extend part way up the sides of the top and bottom plates (1, 2) to facilitate fixing thereto.