| CPC E04F 15/02038 (2013.01) [B27F 1/02 (2013.01); B27N 3/04 (2013.01); B32B 3/06 (2013.01); B32B 21/02 (2013.01); E04C 2/246 (2013.01); E04F 15/02161 (2013.01); E04F 15/041 (2013.01); E04F 15/102 (2013.01); E04F 15/107 (2013.01); B27F 1/00 (2013.01); B27F 1/04 (2013.01); B29B 13/02 (2013.01); B32B 2471/00 (2013.01); B32B 2607/00 (2013.01); B41J 2/03 (2013.01); E04F 2201/0161 (2013.01); E04F 2201/023 (2013.01); E04F 2203/04 (2013.01); E04F 2203/08 (2013.01); Y10T 428/24777 (2015.01)] | 20 Claims | 

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               1. Building panels, each building panel having a surface layer and a core, 
            wherein the core and the surface layer comprise a thermoplastic material, 
                wherein at least three core grooves are provided in a rear side of the building panels with an opening towards the rear side, and 
                wherein an area of the rear side is less than about 80% of an area of the surface layer, 
                wherein at least two of the core grooves have different groove depths. 
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