Brickwork strictly speaking is understood by the trade to mean work executed with standard-sized bricks, i.e. 9 inches long, 4 1/2 inches wide, and from 2 1/2 to 3 1/2 inches high, and any larger-sized materials used are considered out of the province of the bricklayer.
The principal point which the bricklayer must always have in view in his work, beyond good workmanship, with the good materials given to him, is to have one pervading bond throughout each separate piece of work, so that the many bricks used will form one continuous unbroken mass from every point of view. By this word bond - which is the very essence of sound work - is meant the arrangement of the bricks in such positions beside and above each other, that no single vertical joint between any two bricks is immediately in line and above that between two others; that is to say, the bricks must always break joint on the solid surface of a brick beneath.
A straight vertical joint between two bricks exactly over a similar joint of the course below is exceedingly bad construction, and an unsound, weak piece of work, which should never be overlooked. Moreover, in good bond the bricks should break joint vertically both in the length and thickness of the wall, so as to bind the several bricks forming the mass into one solid piece of work, and fairly to distribute the superincumbent weight.
Fig. 30 illustrates this principle of breaking joint, and also its object and effect in distributing the load, as the dotted lines show how it is carried from one brick on to the centres of the bricks below.
Fig. 31 shows a piece of walling with no bond, or breaking joints and fig. 32 the effect a heavy load would have on an unsound foundation; the bricks immediately underneath the weight would sink down, and leave those adjacent to them, on each side, in their original position. The same applies to the thickness of the wall as well as to its length, as shown in figs. 33, 34, and 35, on the same principle.
Having shown the necessity for such a principle, to break joints and effect a bond both lengthwise and crosswise, it will be convenient, before proceeding, to explain the modes of carrying out that principle: first, to note that all longitudinal joints, or the beds of the bricks, must be perfectly horizontal, so that the vertical joints can be made perfectly perpendicular without unnecessary trouble, inasmuch as all bricks are, or should be, made rectangular in form on all sides.
The standard size of a brick being 9 inches long, 4 1/2 inches wide, and 3 inches deep, the brick is twice as long as it is broad. The necessity of this proportion is illustrated by the vertical transverse section of a 9-inch wall, properly bonded, as shown in fig. 36; from which it will be obvious that the front and back surfaces of this wall would be uneven - i.e., in and out each alternate course - if the two small sections were not the exact equivalent, in form and dimensions, of the one long one. Fig. 37 shows the result of such a defect. Of course, a little must be allowed for the mortar joint; and for this purpose the width of a brick is always barely 4 1/2 inches - say, generally about 4 3/8 inches - thus leaving a quarter of an inch joint in 9 inches, which should scarcely ever be exceeded.
From these illustrations it will be obvious that, with the use of bricks of one standard and regular size, the bond must be obtained by laying the tricks in different directions - one course transversely with two others longitudinally side by side, and so on.
A brick which measures, when laid, 9 inches long and 3 inches high on the face or back of a wall, is called a stretcher; and one which shows 4 1/2 inches long and 3 inches high is called a header; and consequently a whole horizontal course of stretchers only is called a stretching course, and one of headers alone a heading course.
The thickness of a brick wall is either defined by inches or by the number of header bricks; a 9-inch wall being described as a 1-brick wall, a 14-inch as a 1 1/2-brick, an 18-inch as a 2-brick wall, etc.
Now, we know that when stretchers are laid in every course, we have a bond in which the bricks of every course break joint over the centre of the bricks below, as shown on fig. 30. But if you use one course of headers and