Thermal and Moisture Protection 183application of flashing cement and a 6-inch-wide felt strip
will minimize the deleterious effects of uneven joints on
the roofing membrane, movement of the units, and mois-
ture transmission through the joint; it also reduces the pos-
sibility of bitumen seepage into the building. The linear
footage of joints to be covered must be determined for
pricing purposes.
14–13 CORRUGATED SHEETS
(INCLUDING RIBBED, V-BEAM)
Corrugated sheets may be made of aluminum, galvanized
steel, and various combinations of materials such as zinc-
coated steel. They are available in various sizes, thicknesses,
and corrugation shapes and sizes, in a wide range of finishes.
Common steel gauges of from 12 to 29 are available with
lengths of 5 to 12 feet and widths of 22 to 36 inches. Alu-
minum thicknesses of 0.024, 0.032, 0.040, and 0.050 inches
are most commonly found, with sheet sizes in widths of 35
and 48^1 ⁄ 3 inches and lengths of 3 through 30 feet.
Estimate the corrugated sheets by the square; note the
type of fastening required. Corrugated sheets require that
corrugated closures seal them at the ends. The enclosures
may be metal or rubber and are estimated by the linear foot.
The amount of end and side lap must also be considered
when estimating the quantities involved. Because of the vari-
ety of allowances, it is not possible to include them here.
Given the information, the supplier or manufacturer’s repre-
sentative will supply the required information. Fasteners
should be noncorrosive and may consist of self-taping
screws, weldable studs, cleats, and clips. The specifications
and manufacturers’ recommendations should be checked to
determine spacing and any other special requirements; only
then can the number of fasteners be estimated. Flashing and
required trim should be estimated by the linear foot.
14–14 Metal Roofing
Materials used in metal roofing include steel (painted,
tinned, and galvanized), copper, and terne. Basically, in this
portion we are considering flat and sheet roofing. The basic
approach to estimating this type is the same as that used for
other types of roofing: first the number of squares to be cov-
ered must be determined; then consideration must be given
to available sheet sizes (often 14 20 inches and 20 28
inches for tin) and quantity in a box. Items that require
special attention are the fastening methods and the type of
ridge and seam treatment.
Copper roofing comes in various sizes. The weights
range from 14 to 20 ounces per square foot, and the copper
selected is designated by its weight (16-ounce copper). The
copper may have various types of joining methods; among
the most popular are standing seam and flat seam. The esti-
mator must study the drawings and specifications carefully,
as the type of seam will affect the coverage of a copper sheet.
When using a standing seam, 2^1 ⁄ 4 inches in width are lost
from the sheet size (in actual coverage) to make the seam.
This means that when standing seams are used, 12 percent
must be added to the area being covered to allow for the
forming of the seam; if end seams are required, an allowance
must also be added for them. Each different roofing condi-
tion must be planned to ensure a proper allowance for
seams, laps, and waste.14–15 Slate
Slate is available in widths of 6 to 16 inches and lengths of
12 to 26 inches. Not all sizes are readily available, and it may
be necessary to check the manufacturer’s current inventory.
The basic colors are blue-black, gray, and green. Slate may
be purchased smooth or rough textured. Slate shingles are
usually priced by the amount required to cover a square if
the manufacturer’s recommended exposure is used. If the
exposure is different from the manufacturer’s, Formulas 14-2
and 14-3 (Section 14–17) may be used. To the squares
required for the roof area, add 1 sf per foot of length for
hips and rafters. Slate thicknesses and corresponding
weights are shown in Figure 14.11, assuming a 3-inch lap.
Each shingle is fastened with two large-head, solid copper
nails, 1^1 ⁄ 4 or 1^1 ⁄ 2 inches long. The felt required under the slate
shingles must also be included in the estimate. Waste for
slate shingles varies from 8 to 20 percent, depending on the
shape, number of irregularities, and number of intersec-
tions on the roof.14–16 Tile
The materials used for roofing tiles are cement, metals, and
clay. To estimate the quantities required, the roof areas are
obtained in the manner described earlier. The number, or
linear footage, of all special pieces and shapes required for
ridges, hips, hip starters, terminals, and any other specialFIGURE 14.11.Approximate Weight of Slate per Square.