Abstract: A roofing structure includes a plurality of beams supporting an inner skin of cladding material. The inner skin of cladding material is secured to the beams by U-shaped brackets. An inverted U-shaped rail nested with pairs of brackets is clamped to the brackets by means of a nut and bolt to define a box-like support structure.An outer skin of cladding material is secured to the rails. Each bracket is provided with locating holes which can be engaged by a bolt and on which the rail can be nested to effect alignment between the fastening slots respectively in the bracket and the rail just prior to clamping.