The manner in which the bricks are arranged in the work, is termed bond, and is of different kinds, according to the thickness of the wall, and the purposes for which it is intended. The bond most generally used is termed Flemish, in which the bricks are laid alternately lengthwise and across the thickness of the wall, the broadest side of the brick being laid horizontal, and never edgeways, in building walls of every thickness. It was formerly usual to lay a whole course of bricks lengthwise, and that above it across; this disposition may be seen in old walls, and was termed English-bond. In every kind of bond, the joints of the bricks of one course are always made to fall over a brick in that beneath, or so that one joint may never be immediately over another.
The site of a wall, or the walls of a building, being set out or marked on the ground, a trench is dug in the earth for the foundations, the width and depth being determined on from the thickness and height of the superstructure, and from the nature of the soil. If this be loose or soft, and the edifice be an important one, it is often necessary to drive piles into the bottom of the trench, and lay a course of oak planking on the tops of these timbers, to form a firm foundation for the wall; but if the nature of the ground do not require such precautions, it is only necessary to level the bottom of the trench carefully, as on this the stability of the wall will entirely depend. A course of bricks is then laid dry on the earth, forming a band twice the width of the lowermost thickness of the wall to be built. This and the subsequent courses of the foundations should be constructed of the best bricks; but unfortunately in common houses this obvious requisite is entirely neglected. When this course is laid, thin mortar, or mortar almost fluid and having but little sand in it, is poured over the bricks, so as to flow into the joints and bind them together by hardening: a second course is then laid on the first, only narrower in width, and each subsequent course diminishes in the same regular manner on each side, till the width is reduced to the thickness at which it is proposed that the lower part of the wall should be built. A cross section of these foundations thus constructed would present the outline of a truncated pyramid, diminishing by regular sets-off or steps; this part of a wall is called the footings. For garden walls, or such as have no weight to carry, the footings need not be made of so many courses, nor so broad, but every wall must have two courses at least for a foundation.
The bricklayer makes use of a string stretched between two pins, to enable him to keep his work straight; and he lays the outermost bricks, those forming the face of the wall, carefully by this guide, setting each brick alternately lengthwise and transversely, and spreading a layer of mortar on the brick beneath, to form a bed for the new one to lie on, and also a layer between each upright joint. It is usual only to lay the outer bricks in this manner, and to fill up the interstices of those forming the interior of the wall by pouring mortar on each course previously laid dry with sufficient interval between them. The workman as he proceeds, repeatedly makes use of his level and square; by the former, he examines whether the face of his wall, and all the corners, or arrises, are correctly perpendicular, and whether the courses of bricks are laid horizontal.
Apertures, such as windows or doors which are to be formed in the wall, are marked out on the wall when the work is built up to the height where they are to commence; in carrying up the piers between these windows, it will frequently happen that the width of the pier is not precisely commensurate with a certain number of bricks or half-bricks, but that a brick must be cut to bring the work to the correct dimensions. This smaller piece is termed a closure, and is usually placed within a brick or two of the arris of the window or door, and preserves its place for the whole height of the pier.
The thickness of brick walls is described by the number of bricks’ length they contain in that direction: thus a nine-inch wall is one-brick thick; a brick-and-a-half wall is fourteen inches; a two-brick wall is eighteen inches thick, and so on. The walls of small houses are often only one brick thick, even when they are two stories high; but usually a wall to be steady should decrease in thickness half a brick at least every story, and for a large substantial building of four or five stories, the main walls should be two-and-a-half bricks at least on the basement story, and one-and-a-half at the top; but of course the size of the apartments, or, in fact, the area of wall which is to remain without any lateral support, must govern the strength of it, as well as the total height to which it is to be raised.
When the wall is raised as high as the tops of the windows, &c., which were left in it, these apertures must have arches turned over them, to support the brick-work above. This leads us to consider the different modes of constructing brick arches. When the width of the opening is not above three or four feet, the arch over it is frequently straight in its outline, or but slightly curved in the intrado or lower line. The bricks which are to form the arch are rubbed down on a board till they are brought to the proper wedge form. A piece of wood for a centering is supported in the opening by upright slips: the upper side of this centering is, of course, cut to the true camber or curve the intrado of the arch is to have: the bricks are set upright on this centre, and alternately, so as to break the joints. The face of the arch, which is seen in the street over the windows and doors, is constructed of the best bricks, carefully cut to a mould and set in putty, or in thin mortar made of lime only: the rest of the arch behind this face is less carefully constructed, and the bricks are often not cut at all, but made to form an arch by the intervening layer of mortar being spread unequally thick, or in a wedge shape. When, however, a large arch is to be built of bricks, these are cut to the proper level to form the wedge-shaped voussoirs. The construction of groined arches in brick-work is the most difficult operation in the trade. Each brick that forms the arris or intersection of the cross vaults requires to be cut to a true form given by a drawing made to the full size on a board. Another perhaps still more delicate piece of workmanship for a bricklayer to execute is an oblique arch, such as are often seen in the bridges over railroads and canals, which cut established roadways obliquely. These arches are portions of a cylinder, but the ends of the cylinder, instead of being perpendicular to the axis, are oblique to it, and this requires that the courses of bricks composing the arch shall also not be parallel to the axis, and therefore not in straight lines: hence, every brick has to be cut or rubbed to a wedge form in two directions, and great nicety in this and the subsequent operations are requisite in these structures.
Formerly columns, pilasters, cornices, niches, and similar architectural embellishments, were constructed in brick-work, but stone has now superseded brick for all embellishments; and the bricklayer’s greatest skill is only required in the construction of arches, or occasionally building a circular wall. The best specimens of elaborate brick-work of the old school may be seen at the conservatory of Kensington Palace, at Burlington House, and many other edifices of the time of William and Mary, and Queen Anne, throughout the country. The series of arches extending for nearly four miles on the Greenwich Railway, and those for nearly an equal distance on the Blackwall Railway, are perhaps among the best and most imposing specimens of modern brick-work, and afford, in many places, beautiful examples of the oblique arch. There are brick arches of a large span at each end of the new London and Waterloo bridges.
Brick-work is measured by the rod, which is a superficial area of sixteen and a half feet each side, or 272 square feet, at a thickness of one-and-a-half brick, and all plain wall-work is reduced to this standard for valuation. A rod of brick-work contains 4500 bricks, and together with the mortar required to build it, weighs about 15 tons 8 cwt. It differs in value from 10l. to 15l., according to circumstances.
Besides building walls, bricklayers are employed to tile roofs, set coppers, pave stables, &c., build drains, and, in short, on all occasions where bricks or tiles are the materials used.