Ondulit multilayer roof is solid since its mechanical and thermal expansion features are those specific to steel,  constituting the internal substrate of the panel. Steel offers the greatest tensile strength and the lowest thermal expansion values in comparison to the most commonly used roofing products.

Higher tensile strength assures infrangibility, safety foot traffic, no breaks and larger spanning of the supporting structure. The embossing of the external metal foils and the plastic interposed layers make totally thermal expansions of the different layers compatible.

Lower thermal expansion enables the use of longer panels, avoiding overlapping and at the same time, risks disruptive processes caused by expansion between panels and the supporting structure.