### Measurement

In measuring slating, the method of determining the number of slates required per square is similar to that given for shingling; but, in slating, each course overlaps only two of the courses below, instead of three, as in shingling. The usual lap, or cover of the lowest course of slate by the uppermost of the three overlapping courses, is 3 in.; hence to find the exposed length, deduct the lap from the length of the slate, and divide the remainder by 2. The exposed area is the width of the slate multiplied by this exposed length, and the number required per square is found by dividing 14,400 by the exposed area of 1 slate.

Thus, if 14" X 20" slates are to be used, the exposed length will be (20-3) / 2= 8 1/2 in.; the exposed area will be 14 x 8 1/2

= 119 sq. in., and the number per square will be 14,400 / 119 = 121 slates.

The following rules should be observed in measuring slating: Eaves, hips, valleys, and cuttings against walls are measured extra, 1 ft. wide by their whole length, the extra charge being made for waste of material and the increased labor required in cutting and fitting. Openings less than 3 sq. ft. are not deducted, and all cuttings around them are measured extra. Extra charges are also made for borders, figures, and any change of color of the work, and for steeples, towers, and perpendicular surfaces.

The following table, based on 3" lap, gives the sizes of the American slates, and the number of pieces required per square.

## Number Of Slates Per Square

 Inches. Number of Pieces. Size. Inches. Number of Pieces. Size.Inches. Number Pieces. 6X12 533 9X16 246 14X20 121 7X12 457 10X16 221 11X22 138 8X12 400 9X18 218 12X22 126 9X12 355 10X18 192 13X22 116 7X11 374 11X18 171 14X22 108 8X 14 327 12X18 160 12X24 114 9X 11 291 10X20 169 13X24 106 10X14 261 11X20 154 11X24 98 8X16 277 12X20 141 16X24 86

## Cost. - The Cost Of Slating May Be Estimated As Follows:

 Cost of 1 Square of Slating. Slates, 8 in. X 12 in............................................................. \$5.00 Labor: 1 slater will average 2 squares per day; wages being \$2.00 per day, 1 square will cost............................ 1.00 Nails, 8" X 12" slates require 5 lb. 9 oz. (5.6 lb.) of galvanized nails per square, which, at \$2.20 per 100 lb., cost. .12 Roofing felt, 1 roll............................................................. 2.40 Labor and nails for applying felt...................................... .15 Flashing will cost about 10 cents per sq. ft.......................Cost per square ........................................................ \$8.67

This figure is exclusive of roof sheathing, the cost of which may be estimated as shown for hemlock framing, on page 340.

The cost of slating per square varies from 7 to 13 cents per sq. ft., depending on the class of work.