The bitumen mastic shall be applied in one or three coats, as stated below, to all surfaces, whether sloping, horizontal, or vertical. The thickness shall be as follows- 1. A 10mm bitumen mastic shall be laid in one coat for walls and floors above ground level. 2. For vertical surfaces and for the surfaces steeper than 30 degrees, the bitumen mastic shall be applied in three coats which shall be less than 20mm totally.  3. For horizontal surfaces and for the sloping surfaces not steeper than 30 degrees, the bitumen mastic shall be applied in three coats which shall be less than 30mm totally.