Bituminous or Roofing Felt is a glass fibre or polyester fleece impregnated with bituminous material e.g. tar or bitumen which is produced in roll form and is used as a waterproof material for roof covering.
In some cases, sand is applied on one side to help prevent the material from sticking together while in roll form and to provide protection from atmospheric conditions. However, many new pitched roofs now use more advanced membranes for increased protection against leaks.
Although only recently introduced, these are more durable and less prone to puncture and tear and are lighter and stronger. There are also breathable variations permeable to water vapour which when used in conjunction with proper ventilation, help to minimize condensation in roof spaces.