93. Black sheet iron for roofing is furnished cold rolled and annealed, in gauges ranging from 16 to 26 and in weight from 3/4 pound to 2 1/2 pounds per square foot. Anything lighter than gauge 26 is not recommended. The sizes of the sheets vary from 24 in. X 72 in. for the lighter gauges to 30 in. x 84 in. for the heavier weight. The sheets should be free from flaws or holes, and uniform in thickness and ductility.

Paper and felt are not, as a rule, used under iron, but their use, it should be observed, tends to make the roof more enduring, protecting it from gases underneath and from sweating.

94. Sheet iron is usually laid with some form of standing seam, with or without a cap, on the interlocking pattern, with the same kind of joint as in the case of metal tiles or shingles.

Standing seam roofing with cap is prepared by locking and seaming the sheets together, end to end, thus forming a continuous sheet the full length of the slope of the roof. The edges are then turned up or flanged 1 inch high (see a, inches wide, having a bearing on the roof of 2 in. X 1 1/2 in. The upstanding part of the cleats is cut down the middle, as at b, 1 3/8 inches, and one section c of the divided cleat is bent over the flange of the sheet d first laid. The sheets of the second row c are then flanged and placed against the clip a, whose other half b is turned over this flange.

Fig. 77. The flange b of the eaves gutter should lap on the roof 4 inches.

The outside edge c is bent down over the gable facia at least 1 inch, and nailed. The standing seams are secured with cleats a, Fig. 78; these are made of metal 2

Black Sheet Iron Roofing 307

Fig. 77.

Black Sheet Iron Roofing 308

Fig. 78.

The flanges are then gone over, clamped or seamed up close and tight, and the cap g is put on. This cap should be clamped securely in place. Holes h are then punched through the cap and flanges about 15 or 16 inches apart, and 1/8-inch rivets are used to bind the parts together. A washer should be placed on each end of the rivet, and the head should be formed with a rivet set.

Hips, in this style of roofing, are made by cutting the sheets to the proper angles, but making an allowance of 2 inches, then turning or flanging this 2-inch section, and capping it in the same way as the other joints.

Valleys are formed of full-width sheets, 24 inches broad. A 1/2-inch single lock is formed on the sheets on each edge of the valley, which should be secured to the roof with clips to fit the lock, as in flat seam tin roofing. A flat lock is then formed on the roofing sheet, and both are locked together and seamed down.

Flashings are constructed in the same manner as for the metal roofs already described.

95. Double-seamed roofing, shown in Fig. 79, has another form of standing seam. This roofing is put up in rolls, the same as capped roofing, and the sheets are joined end to end by a single lock seam. It may be at once seen that with this roofing no caps or fastenings of any kind are used, except the cleats a, which are nailed to the roof at the same centers as for cap roofing. The sheets are turned up \\ inches on one side c, and 1 1/2 inches on the side b. The 1 1/2-inch side is turned over the 1 1/4-inch side, as at d, and the whole seam is then turned over and down again, forming the double seam e, from which the roofing obtains its name. The flashings are the same as those before described. This method guarantees an enduring and perfectly water-tight roof.

Black Sheet Iron Roofing 309

Fig. 79.

96. The interlocking pattern (see Fig. 80) consists of sheets with a single lock a at the top and bottom of the sheets, and at the sides a vertical lock b. The plates are attached to the roof by nailing through the side flange c. The chief merits of this method are that no cleats, rivets, or anchors are employed, and a great saving of time and labor is effected. The roof appears as if laid with rolls, and the peculiar pattern of the side lock gives the roof strength and makes it very rigid and durable.

Black Sheet Iron Roofing 310

Fig. 80.

97. The following table gives the gauge, thickness, and weight, in pounds of black sheet iron per square foot:

Table 12

Gauge Number.

Thickness. Inch.

Weight.

Pounds per

Square Foot.

16

.065

2.61

17

.058

2.33

18

.049

1.97

19

.042

1.69

20

.035

1.40

21

.032

1.28

22

.028

1.12

23

.025

1.00

24

.022

0.88

25

.020

0.80

26

.018

0.72

27

.016

0.04

28

.014

0.56