Built up felt roofing compromises of bituminous based reinforced sheets, delivered to site in rolls, which can be installed in multiple layers (commonly three). The reinforcement can be glass fibre or polyester and the bitumen, oxidised or polymer modified with APP or SBS molecules. The system can be bonded in hot bitumen, which is melted in a cauldron, (roll and pour), glued, torch on or mechanically fixed. Insulation if required can be introduced to create a warm or inverted roof. Finishes can be factory applied slate slithers, stone chippings, ballast, slabs, timber decking, garden roofs etc. The membrane can be installed to any degree of pitch.