PART C - ROOF-COVERING MATERIAL
Many different kinds of roof-covering materials are available, including tile, built-up roofing, asphalt
shingles, mineral fiber (asbestos-cement) shingles, and wood shines. Carpenters mainly work with the
last three.
3-14. Roof Sheathing. Plywood or one-by material is satisfactory for sheathing roofs. Plywood is
more economical than one-by material, and it can be installed rapidly. The thickness required is 3/8,
1/2, 5/8, or 3/4 inch depending on the rafter spacing, pitch, and load on the roof. When installing
sheathing, be sure that the joints are placed over the rafters. The roof sheathing should be arranged so
that the joints for the complete roof are staggered.
3-15. Roof-Covering Terms. These terms should be understood before proceeding with this part.
a. Square. Roofing is estimated and sold by the square. A square is the number of shingles
required to cover 100 square feet of roof surfaces.
b. Coverage. Shingles overlap, and depending on the manner in which they are laid, one, two,
or three thicknesses cover the roof at any one place. The roofing is termed single coverage, double
coverage, and so on.
c. Shingle Butt. The shingle butt is the lower exposed edge of the shingle.
d. Exposure. The exposure is the distance from the butt of one shingle to the butt of the
shingle above it. This is the portion of the shingle that is exposed to the weather.
e. Underlayment. The underlayment is the application of saturated felt that is placed over the
roof surface to protect the roof sheathing until the shingles are applied.
f. Toplap. The width of the shingles minus the exposure.
3-16. Shingle Roof. An asphalt-shingle roof begins with the application of a drip edge, followed by
underlayment (felt) and eave flashing strips. Then, the first full shingle is inverted and nailed in place.
Asphalt roofing comes in rolls (usually 3 feet wide), called rolled roofing; in rolled strips (usually 15
inches wide and 3 feet long); and as individual shingles. The type most commonly used is the flat strip,
often called a strip shingle. The size of a square-butt strip shingle is 12 by 36 inches. This shingle
should be laid 5 inches to the weather, meaning 7 inches of each course should be overlapped by the
next higher course. There are various types of shingles. Figure 3-33 shows a butt shingle with three
tabs.
EN5156
3-26
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