The cost of slating varies from 7 to 9 cents per square foot, depending on the class of work.

28. Tin Roofs

Tin Roofs. In estimating tin (and also other metal) roofs, hips and valleys are measured extra their entire length by 1 foot in width, to compensate for increased labor and waste of material in cutting and laying. Gutters and conductor pipes and leaders are measured by the lineal foot, 1 foot extra being added for each angle. All flashings and crestings are measured by the lineal foot. For seams, addition is made to superficial area, depending on the kind of seam used, whether single lock, standing, or roll and cap. No deductions are made for openings (chimneys, skylights, ventilators, or dormer-windows), if less than 50 square feet in area; if between 50 and 100 square feet, one-half the area is deducted; if over 100 square feet, the whole opening is deducted. An extra charge is made for labor and waste of material to flash around such openings.

A box of roofing tin contains 112 sheets 14 in. X 20 in., and weighs from 110 to 145 pounds per box, according to whether it is IC or IX plate. The IC plate, which is the most used, weighs about 8 ounces per square foot, and the IX, about 10 ounces. As there are considerable variations in the weights of tin made by different manufacturers, a fair average will be obtained by estimating IC tin at 1 pound, and IX tin at 1 1/4 pounds per sheet. Double-size roofing tin can be had 20 in. X 28 in., weighing, if IC, 225 pounds per box. This size is the most economical, as by its use much material and labor are saved, on account of the less number of seams and ribs required.

A 14" X 20" sheet will cover about 235 square inches of surface, using standing joints; or a box will cover about 182 square feet. With a flat lock seam, a sheet will cover 255 square inches, allowing 3/8 inch all around for joints; or a box will lay 198 square feet. These figures make no allowance for waste.

Two good workmen can put on, and paint outside, from 250 to 300 square feet of tin roofing per day of 8 hours.

Tin roofing will cost from 8 to 10 cents per square foot, depending on the quality of material and workmanship.

29. Tile roofs are constructed of so many styles of tile that no general rules of measurement can be given, and every piece of work must be estimated according to the particular kind of tile used and the number of sizes and patterns. Information on all these points are to be found in the catalogues of tile manufacturers.

30. In gravel roofing the cost per square depends upon the number of thicknesses of tarred felt and the quantity of pitch used per square.