E04C 2/28

Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials composed of materials covered by two or more of groups [CPC: E04C2/04], [CPC: E04C2/08], [CPC: E04C2/10] or of materials covered by one of these groups with a material not specified in one of the groups combinations of materials fully covered by groups [CPC: E04C2/04] and [CPC: E04C2/08]