Combined with other materials, bitumens may be used as vapour barriers and as agents to waterproof and damp-proof structures. Bitumen is used in many forms depending upon the characteristics and properties desired. Saturated felts, used in built-up roofing as a base for prepared roofing and siding, as underlays for floors, and as a membrane for waterproofing, require a particular grade of bitumen that bas a low viscosity at the saturation temperature. The flash-point should be above the saturating temperature, however, and a reasonably low temperature susceptibility is desirable. Prepared roofing products such as shingles and roll roofing consist of saturated felts coated with asphalt.
Care is taken during manufacture to ensure that the coating asphalt is compatible with the saturant.
Bitumens are widely used to provide a waterproof coating to walls and to construct waterproof membranes in buildings and engineering structures. They may be used alone or with felts to build up a membrane. Asphaltic cutbacks and emulsions have their greatest use in road construction and maintenance. With roofing it accounts for about 95 per cent of the asphalt produced in North America. There are still, however, large quantities of asphalt modified by the addition of mineral matter used in the building industry as sealants, acoustical coatings and paints.