In the majority of brick and stone buildings the crushing strength of brickwork need be considered only in connection with piers, arches and under bearing plates or templates. The strength of brickwork varies with the strength of the individual bricks, the quality and composition of the mortar, the workmanship and bond, and also with the age of the brickwork. It is not the purpose here to enter minutely into the subject of the strength of materials, but for general practice the following safe loads may be allowed for the crushing strength of brickwork in the cases above mentioned : For New England hard-burned brick, in lime mortar, 8 to 10 tons per square foot (112 to 138 pounds per square inch).
Same brick in cement and lime mortar, 1 to 3, 14 tons per square foot (194 pounds per square inch).
Same brick in Portland cement and sand mortar, 1 to 2, 15 tons per square foot (200 pounds per square inch).
Average hard-burned Western brick, in Louisville cement mortar, 1 to 2, 10 tons per square foot.
Same brick in Portland cement mortar, 1 to 2, 12½ tons per square foot (175 pounds per square inch).
It should always be remembered that the strength of brick piers depends largely upon the thoroughness with which they are bonded, and the building of all piers should be carefully watched by the superintendent.-
Brickwork is generally measured by the one thousand bricks laid in the wall. The usual custom of brick masons is to take the outside superficial area of the wall (so that the corners are measured twice) and multiply by 15 for an 8 or 9-inch wall, 22½ for a 12 or 13-inch wall and 30 for a 16 or 18-inch wall, the result being in bricks. These figures give about the actual number of bricks required to build the wall in the Eastern States, but in the Western States, where the bricks are larger, they give about one-third more than the actual number of bricks contained in the wall, and the price is regulated accordingly. During the author's experience, in both the Eastern and Western States, he has never known any deviation from these figures by brick masons. In the West two kinds of measurement are known, kiln count being used to designate the actual number of bricks purchased and used, and wall measure, the number of bricks there would be on the basis of 22½ bricks to 1 superficial foot of 12-inch wall.
In regard to deducting for the openings, custom varies in different localities, but unless the openings are unusually large no deduction is generally made for common brickwork. For measuring face brick the superficial area of the wall is taken, with the openings omitted, but if the reveals of the windows are more than 4 inches they are added to the wall area. The number of brick to the superficial foot depends upon the size of the brick used, seven and one-half being the average number.
Where stone trimmings, such as caps, sills, quoins and occasional belt courses are used, if the brick mason sets the stone no deduction is usually made for face brick, but if it is set by another contractor an allowance is sometimes made for the face brick displaced by the stone.
As custom varies considerably in the measurement of brickwork, when the work is done by measurement the contract should distinctly state how the work is to be measured and if deductions are to be made for the openings and stonework. Some builders reduce all the brickwork to cubic feet and estimate the cost in that way for common brickwork.