Building Design and Construction Handbook - Merritt - Ventech!

4.98 SECTION FOUR
4.81.1 Built-Up Roofing
For constructing built-up roofing, four grades of asphalt are recognized (ASTM
D312): Type I, for inclines up to 1 ⁄2 in/ft; Type II, for inclines up to 1 1 ⁄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
150�F, 158 to 176�F, 180 to 200�F and 210 to 225�F, respectively. Heating of the
asphalts should not exceed the flash point, the finished blowing temperature, or
475�F for Type I, 500�F for Type II, 525�F 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 140�F, 106 to 126�F, and
133 to 147�F, respectively.
4.81.2 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 ft 2 ), and standard
coal-tar felts weigh 13 lb per square.
Cotton fabrics are open-weave materials weighing at least 3 1 ⁄2 oz/yd 2 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/yd 2 .
4.81.3 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 ft 2 ), 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.
4.82 ASPHALT SHINGLES
There are three standard types: Type I, uniform or nonuniform thickness; Type II,
thick butt; and Type III, uniform or nonuniform thickness (ASTM D225). Average