The method involves has stuctural or corrugated panels (4-6) with their cutting plane perpedicular to the direction of the undulations and a cut edge which has apices and recesses or valleys formed in it. The undulating panel sections can have reliefs on the structural panels opposing them so that an open cavity structure between the panels is formed. The reliefs of the corrugations can have point fixings. The corrugated panels can be cuerved so that the radius of curvature extends in the plane pof the panels. The upper and lower surfaces of the panel can have an open structure.
