This section is from the book "The Building Trades Pocketbook", by International Correspondence Schools. Also available from Amazon: Building Trades Pocketbook: a Handy Manual of reference on Building Construction.

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.

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 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.

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