This section is from the book "A Treatise On Architecture And Building Construction Vol4: Plumbing And Gas-Fitting, Heating And Ventilation, Painting And Decorating, Estimating And Calculating Quantities", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
Kinds Of Roof Covering. The roof coverings most generally used are shingles, slate, tin, tile, and tarred paper and gravel (known as gravel roofing). While there are slight variations in the methods of measuring the different kinds, they are all based on the square of 100 square feet.
Shingles. In measuring shingle roofing, it is necessary to know the exposed length of a shingle; this is found by deducting 3 inches-the usual cover over the head of the lowest shingle in the four overlapping courses-from the length; dividing the remainder by 3, the result will be the exposed length, and multiplying this by the average width of a shingle, the product will be the exposed area. Dividing 14,400, the number of square inches in a square, by the exposed area of 1 shingle, will give the number required to cover 100 square feet of roof. For example, it is required to compute the number of shingles 18 in. x 4 in. necessary to cover 100 square feet of roof. With a shingle of this length, the exposure will be 18-3/3 = 5 inches; then the exposed area of 1 shingle is 4 in. X5 in., or 20 square inches, and 1 square requires 14,400 ÷ 20 = 720 shingles.
An allowance should always be made for waste in estimating the number of shingles required.
The following table is arranged for shingles from 16 inches to 27 inches in length, 4 inches and 6 inches in width, and for various lengths of exposure:
Exposure to Weather.
No. of Sq. Ft. of Roof
Covered by 1,000
No. of Shingles Required for 100 Sq. Ft of Roof.
4 In. Wide.
6 In. Wide.
4 In. Wide.
6 In. Wide.
Shingles are classed as shaved or breasted, and sawed shingles. The former vary from 18 to 30 inches in length, and are about 1/2 inch thick at the butt and 1/16 inch at the top; the latter are usually from 14 to 18 inches long, and of various thicknesses. In the case of 18-inch shingles, there are 5 shingles to 2 1/4 inches; that is, the thickness at the butt is 2 1/4 ÷ 5 = .45 inch, or about 7/16 inch; and at the top the thickness is 1/ 16 inch.
Strictly first-class shingles are generally given a brand of "XXX," and those of a slightly poorer quality are termed No. 2; but in some sections of the country, the brand "A" is general; thus, "Choice A" or "Standard A" are practically equivalent to the "XXX" shingle.
Shaved shingles are usually packed in bundles of 500, or 2 bundles per thousand. Sawed shingles are made up into bundles of 250, and are sold on a basis of 4 inches width for each shingle. If the wider ones are ordered, the cost per thousand is correspondingly increased. For example, if one thousand 4-inch shingles were required to cover an area, and 6-inch ones were ordered, only two-thirds as many, or GG7, would be needed and furnished, while the cost would be that of 1,000 standard-width shingles.
Shingles cost from $3.00 to $5.00 per thousand, according to material and grade. Dimension shingles-those cut to a uniform width-if of prime cedar, shaved, 1/2 inch thick at the butt and 1/16 inch at the top, will cost $9.00 to $10.00 per thousand, but such shingles are usually 6 inches wide and 24 inches long, so that a less number will be required per square than of ordinary shingles.
A fairly good workman will lay about 1,500 shingles per day of 9 hours, on straight, plain work; while in working around hips and valleys, the average will be about 1,000 per day.