13. Brickwork is generally estimated by the thousand bricks laid in the wall, but measurements by the cubic yard and the perch are also used. The following data will be useful in calculating the number of brick in a wall. For each superficial foot of wall 4 inches (the width of one brick) in thickness, allow 7 1/2 bricks; for a 9-inch (the width of two bricks) wall, count 15 bricks; for a 13-inch (the width of three bricks) wall, allow 22 1/2 bricks; and so on, estimating 7 1/2 bricks for each additional 4 inches in thickness of the wall. The above figures are for the ordinary eastern standard brick, which is about 8 1/2 in. X 4 in. X 2 1/4 in. If smaller brick is used, the figures will be increased proportionately. If brickwork is estimated by the cubic yard, allow 500 brick to a yard. This figure is based on the use of brick of the size above given, and mortar joints not over 3/8 inch thick. If the joints are 1/8 inch thick, as in face brickwork, 1 cubic yard will require about 575 bricks. In making calculations of the number of bricks required, an allowance of, say, 5 per cent. should be made for waste in breakage, etc.

The practice in regard to deductions for openings is not uniform throughout the country, but usually small openings are counted solid, as the cost of the extra labor and the waste in working around these places balances that of the brickwork saved. All large openings, 100 square feet or over in area, should be deducted.

When openings are measured solid, it is not usual to allow extra compensation for arches, pilasters, corbels, etc. Rubbed and ornamental brickwork should be measured separately, and charged for at a special rate.

Brick footings may be computed by the lineal foot. The following table, based on steps or offsets of one-quarter brick, or 2 inches, for each course in the footing, gives the number of bricks per lineal foot in footings for brick walls from 9 to 26 inches thick: