Roofing felt bitumen. Synonym: asphalt roofing felt coated on both sides. It is obtained by impregnating felt cardboard, corresponding to the PN conditions, two-sided asphalt coating and sprinkling with an ingredient of mineral origin, e.g.. talc (to prevent sticking). Depending on the thickness of the felt cardboard, the corresponding No.. bituminous roofing felt: 80, 100 i 150. Roofing felt bitumen, coated on both sides, it should not seep through the water at least within 72 at. at the height of the water column 50 cm. Checking for brittleness and fracture and scratch resistance is similar, as with other types of pap. Rolls may have po 10 i 20 m in length. Roll width and length tolerance - approx 1%, weight tolerance of felt cardboard - up to 5%. Weight breaking the width strip 5 cm, cut from the length or width of the roll, should be for roofing paper No. 80 — 45 kg, No 100 — 40 kg, No 150 — 25 kg. Break elongation - minimum 3%. This roofing felt is used as a top layer, sometimes for insulation and electrical engineering works.