Underley felt

Cardboard underlay for use on wooden foundations, as surface layer of overlay plates (concrete or tile), overlay disks, level plates, roofing felt or die-cut cardboard (shingle). Consists of polyester body (YAP), mineral felt body (YAM), impregnated and coated with oxidised asphalt. YAM recommends use only under surface cardboard and shingle. YAP is recommended under all surface layers.
YEP is the best quality and is prescribed where the stress is considered extra high. For low temperatures or high train during the building period. All grades are approved in accordance with Sitac nd are P-marked.