Estimating in Building Construction

Thermal and Moisture Protection 181

and details should be checked to determine the amount of
overhang and type of finishing required at the overhang.
Openings of less than 30 sf should not be deducted from the
area being roofed.
To determine the area of a gable roof, multiply the
length of the ridge (A to C) by the length of the rafter (A to
B) by two (for the total roof surface). The area of a shed roof
is the length of the ridge (A to C) times the length of rafter
(A to B). The area of a regular hip roof is equal to the area of
a gable roof that has the same span, pitch, and length. The
area of a hip roof may be estimated the same as the area of a
gable roof (the length of roof times the rafter length times
two). However, gable roofs require more materials because
they generate more waste.
The length of rafter is easily determined from the span
of the roof, the overhang, and slope. Refer to Figure 13.49
(Example 13-21) for information required to determine the
lengths of rafters for varying pitches and slopes.

14–11 Shingles

Asphalt Shingles

Available in a variety of colors, styles, and exposures, strip
asphalt shingles are 12 and 15 inches wide and 36 inches
long. They are packed in bundles that contain enough shin-
gles to cover 20, 25, or 33.33 sf of roof area. The exposure
(amount of shingle exposed to the weather) generally is 4,
4.5, or 5 inches. Sometimes individual shingles 12 to 16
inches long are also used. Asphalt shingles may be specified
by the weight per square, which may vary from 180 to 350
pounds. Shingles may be fire-rated and wind resistant,
depending on the type specified.
In determining the area to be covered, always allow one
extra course of shingles at the eaves, as the first course must
always be doubled. Hips and ridges are taken off by the lin-
ear foot and considered 1 foot wide to determine the square
footage of shingles required. Waste averages 5 to 8 percent.
Galvanized, large-headed nails, 1/2 to 1^3 ⁄ 4 inches long, are
used on asphalt shingles. From 1^1 ⁄ 2 to 3 pounds of nails are
required per square.
Asphalt shingles are generally placed over an underlay-
ment of building paper or roofing felt. The felt is specified by
the type of material and weight per square. The felt should
have a minimum top lap of 2 inches and end lap of 4 inches;
to determine the square footage of felt required, multiply the
roof area by a lap and waste factor of 5 to 8 percent.

EXAMPLE 14-3 ASPHALT SHINGLE ROOFING

Using the residence that was introduced in Chapter 13, determine
the felt and shingle requirements. In Example 13-21, the rafter
length of 13.9 feet and ridge length of 52 feet were determined. The
first step is to determine the quantity of 15-pound roofing felt that
is required.

1,446 sf

Roof area13 .9¿ rafter length 52 ¿ ridge length2 sides

Slope: 3 on 12

Felt requirements: 2 layers—lapped 19 inches

Formula 14-1

Felt Coverage

Use 235-pound shingles

Ridge shingles 5-inch exposure



Labor. Subcontractors who specialize in roofing will do

this work, and they may price it on a unit basis (per square)

or a lump sum. The time required to install shingles is shown

in Figure 14.10.

Wood Shingles

Available in various woods—the best of which are cypress,

cedar, and redwood—wood shingles come hand-split (rough

texture) or sawed. The hand-split variety is commonly

Pieces of ridge shingles 624 – > 5 – per shingle125 pieces

Ridge length52 lf 624 –

Order 16 squares

Squares of roofing14.46 squares1.04 squares15.5 squares

Starter course1.04 squares

104 lf (Assume 1¿ wide)

Starter course52 lf of eaves per side2 sides

Use 8 rolls

Rolls of felt required1446 sf>204 sf per roll7.08 rolls

Roll coverage432 sf(17–> 36 – )204 sf

Exposure 36 – – 19– 17 –

ExposureRoll widthLap

Roll coverageSquare feet in roll

Exposure

Width

Square feet of felt in a roll 36 – wide 144 ¿ long432 sf

FIGURE 14.10.Roofing Labor Productivity

Rates.

Labor Hours

Roofing Material per Square

Shingles

Asphalt (strip) 0.8 to 4.0

Asphalt (single) 1.5 to 6.0

Wood (single) 3.0 to 5.0

Metal (single) 3.0 to 6.0

Heavyweight Asphalt Add 50%

Tile

Clay 3.0 to 5.0

Metal 3.5 to 6.0

Built-up

2 Ply 0.8 to 1.4

3 Ply 1.0 to 1.6

4 Ply 1.2 to 2.0

Aggregate Surface 0.3 to 0.5