The number of shingles required for a roof is usually estimated at one thousand for every square, or one hundred square feet; hence, find the square feet in the roof and divide by one hundred, - result is the number of thousand shingles. This estimate is ample, and with good shingles 1000 should lay 125 to 140 feet.

Or, find the area in inches, multiply the width of a shingle by the length exposed to the weather, and divide the area by the product. This gives the number of shingles, but there must be allowance made for waste. Shingles are laid from three to six inches to the weather, according to length, and they vary in width, four inches being the average width.

For clapboarding, - Add one-third to the number of surface feet to be covered, for boards, 6 inches wide, laid 4 1/2 inches to the weather.

For flooring, - add one-fifth to the surface feet, for matching.

In plastering - It is customary to compute the whole area and deduct one-half the area of doors and windows, but in some places no deduction is made.