Brick is generally paid for by the cubic yard or by the thousand, and the bidder must make his own allowance, if necessary, for any extra work due to thin walls. The number of brick per cubic yard depends on the thickness of the joints and on the size of the bricks. A very slight variation in the thickness of the joint will change very materially the number of brick per cubic yard, and also the amount of mortar. The exact values (according to the size of the brick and the thickness of the mortar joint) are as given below; but the values are not closely to be depended on, because of these variations: It is very common and convenient to estimate that 1,000 brick will make two cubic yards of masonry. The number of brick per cubic yard given above is the equivalent of 16, 19, and 20 brick per cubic foot. Bricklayers (backed up by their unions) sometimes de mand pay per 1,000 brick laid, but compute the number on the basis of 7 bricks per superficial foot of a wall 4 inches thick, 15 bricks for a "9-inch wall," and 22 bricks for a "13-inch wall." The number actually used in a 13-inch wall varies from 17 to 20.
154. Cost of Brickwork. A laborer should handle 2,000 brick per hour in loading them from a car to a wagon. If they are not un loaded by dumping, it will require as much time again to unload them. A mason should lay from 1,200 to 1,500 brick per 9-hour day on ordinary wall work. For large, massive foundation work with thick walls, the number should rise to 3,000 per day. On the other hand, the number may drop to 200 or 300 on the best grade of pressed brick work. About one helper is required for each mason. Masons' wages vary from 40 to 60 cents per hour; helpers' wages are about one-half as much.
155. Impermeability. As previously stated, brick is very porous; ordinary cement mortar is not water-tight; and therefore, when it is desirable to make brick masonry impervious to water, some special method must be adopted as described in Part I, under the head of "Waterproofing."
156. Efflorescence. This name is applied to the white deposit which frequently forms on brickwork and concrete, arid has already been described in Part I. The Sylvester wash has frequently been used as a preventive, and with fairly good results. Diluted acid has been used successfully to remove the efflorescence. These methods have already been described in Part I.
157. Brick Piers. A brick pier, as a general rule, is the only form of brickwork that is subjected to its full resistance. Sections of walls under bearing plates also receive a comparatively large load; but only a few courses receive the.full load, and therefore a greater unit-stress may be allowed than for piers.
Kidder gives the following formulte for the safe strength of brick piers exceeding 6 diameters in height: In the above formulae, II is the height of the column in feet, and D is the diameter of the column in feet.
For example, a column 16 feet in height and 11 feet square, laid with rich lime mortar, may be subjected to a load of 65 pounds per square inch, or 9,360 pounds per square foot; for a 1 to 2 natural cement mortar, 90 pounds per square inch, or 12,960 pounds per square foot; and for a 1 to 3 Portland cement mortar, 146 pounds per square inch, or 20,914 pounds per square foot.
The building laws of some cities require a bonding stone spaced every 3 to 4 feet, when brick piers arc used This stone is 5 to S inches thick, and is the full size of the pier. Engineers and archi tects are divided in their opinion as to the results obtained by using the bonding stone.