Hot asphalt or coal tar are used for conventional built-up roofing. The bitumens are heated to a high enough temperature to fuse with saturant bitumen in roofing felts, thus welding the plies together. The optimum temperature at the point of application for achieving complete fusion, optimum mopping properties, and the desirable interply mopping weight is called the equiviscous temperature (EVT). Information on EVT should be obtained from the manufacturer.
Built-Up Roofing
For constructing built-up roofing, four grades of asphalt are recognized (ASTM D312): Type I, for inclines up to 1â„2 in / ft; Type II, for inclines up to 11â„2 in / ft;
Type III, for inclines up to 3 in/ ft; and Type IV, suited for inclines up to 6 in/ ft, generally in areas with relatively high year-round temperatures. Types I through IV may be either smooth or surfaced with slag or gravel. Softening ranges are 135 to 150F, 158 to 176F, 180 to 200F and 210 to 225F, respectively. Heating of the asphalts should not exceed the flash point, the finished blowing temperature, or 475F for Type I, 500F for Type II, 525F for Types III and IV.
Coal-tar pitches for roofing, dampproofing, and waterproofing are of three types (ASTM D450): Type I, for built-up roofing systems; Type II, for dampproofing and membranes waterproofing systems; Type III, for built-up roofing, but containing less volatiles than Type I. Softening ranges are 126 to 140F, 106 to 126F, and 133 to 147F, respectively.
Roofing Felts
For built-up waterproofing and roofing, types of membranes employed include felt (ASTM D226, D227) and cotton fabrics (ASTM D173). Felts are felted sheets of inorganic or organic fibers saturated with asphalt or coal tar conforming to ASTM D312 and D450.
Standard asphalt felts weigh 15, 20, or 30 lb per square (100 ft2), and standard coal-tar felts weigh 13 lb per square.
Cotton fabrics are open-weave materials weighing at least 31â„2 oz/yd2 before saturation, with thread counts of 24 to 32 per inch. The saturants are either asphalts or coal tars. The saturated fabrics must weigh at least 10 oz/yd2.
Roll Roofing
Asphalt roll roofing, shingles, and siding consist basically of roofing felt, first uniformly impregnated with hot asphaltic saturant and then coated on each side with at least one layer of a hot asphaltic coating and compounded with a water-insoluble mineral filler. The bottom or reverse side, in each instance, is covered with some suitable material, like powdered mica, to prevent sticking in the package or roll.
Granule-surfaced roll roofing (ASTM D249) is covered uniformly on the weather side with crushed mineral granules, such as slate. Minimum weight of the finished roofing should be 81 to 83 lb per square (100 ft2), and the granular coating should weigh at least 18.5 lb per square.
Roll roofing (ASTM 224), surfaced with powdered talc or mica, is made in two grades, 39.8 and 54.6 lb per square, of which at least 18 lb must be the surfacing material.
