Bituminous waterproofing

Bituminous waterproofing systems are designed to protect residential and commercial buildings. Bitumen (asphalt or coal-tar) is a mixed substance made up of organic liquids that are highly sticky, viscous, and waterproof. These systems are sometimes used to construct roofs.

Roofing felt

'Roofing felt The term felt comes from the historical method of making the base material. Felt is an unwoven fabric that is produced by matting fibres under pressure. The fibres form the structure of the fabric.

Roofing felt (formerly tar paper) is the base material used to make roof shingles and roll roofing. Typical uses of felt paper are as an underlay(ment) (sarking) beneath other building materials, particularly roofing and siding materials, and is one type of membrane used in asphalt built up roofing (BUR) systems. The purposes are to "...separate the roof covering from the roof deck...shed water...[and] provide secondary weather protection..." Also, the rapid application of roofing underlay protects the roof deck during construction until the roofing material is applied and is required for roofs required to meet Underwriters Laboratory (UL) fire ratings. The separation of the roof covering from the roof deck protects the roof covering from resins in some sheathing materials and cushions unevenness and old nails and splinters in re-roofing applications. The underlayment also sheds water, which penetrates the roof covering from an ordinary leak, a leak from wind-driven rain or snow, wind damage to the roof covering, or ice dams. However, the application of underlays may increase the roof temperature, which is the leading cause of ageing of asphalt shingles and felt paper wrinkles when it gets wet, which (rarely) shows through asphalt shingles. Not installing an underlay may void the roof covering warranty.