IN order to obtain good brickwork the following points should be attended to.
A good bond should be preserved throughout the work, both laterally and transversely. All bed joints should be perpendicular to the pressure upon them; that is, horizontal in vertical walls, radial in arches, and at right angles to the slope of battering walls.1
In walling, the courses must be kept perfectly horizontal, and the arrises plumb. The vertical joints should be directly over one another, - this is technically called "keeping the perpends," - if it is neglected the courses are overrun and "bats" become necessary.
The joints should all be full of mortar, close, well flushed up, and neatly struck or pointed as required.
In good brickwork they should not exceed 3/8 inch in thickness, but with badly-shaped rough bricks the beds of mortar are necessarily made thicker, in order to prevent the irregularities of the bricks from bearing upon one another, and causing fracture.
Both bricks and mortar-joints should be of uniform size and quality in all parts of the work.
As stated in the chapter on materials (Part III.) bricks are made of different sizes; but by far the most common in England are those about 8 3/4 or 9 inches long, 4 1/4 to 4 1/2 inches wide, and 2 1/2 to 2 3/4 inches thick, which alone will here be treated upon.
Bricks of all dimensions are laid on the same principles.
1 A "battering " wall is one which is not vertical, but built with an inclination or "baiter."
In nearly all cases bricks built in walling are laid upon their sides, occupying 9 inches x 4 1/2 inches on plan.
A course is a horizontal slice of the wall taken between two bed joints, and is of a depth equal to that of a brick and one mortar joint. A "bat" is a broken brick, and is called a 3/4 bat, 1/2 bat, etc., according to the proportion it bears to a whole brick.
Headers are bricks whose lengths lie across the thickness of the wall. Those visible on the outside of the wall each show an end in the face, or back.
Stretchers are the bricks which lie parallel to the length of the wall. Those visible on the exterior each show one side in the face, or back of the wall.
Heading courses are those showing no bricks but headers in the face.
Stretching courses are those containing in the face stretchers only.
The thickness of a wall is the distance from the face to back, and is expressed in terms of a brick, thus: - a half-brick wall is 4 1/2 inches thick; a one-brick wall is 9 inches thick; a brick and a half wall is 13 1/2 inches (generally called 14 inches) thick, and so on.
It is often specified that 4 courses should not exceed 12 inches in height. This assumes 2 1/2 for the thickness of each brick and 1/2 for each joint. It is better however to specify that the depth of 4 courses should not exceed the thickness of 4 dry bricks, of the kind to be used, by more than 4 x -3/8" or 4 times whatever thickness of mortar joint is decided upon.
It was there shown that a wall may appear on the face to be well bonded, when in fact there is no bond at all between its front and back.
Fig. 19 shows a wall composed of courses of headers and stretchers alternately. By this arrangement thorough bond is obtained across the thickness of the wall, as each header overlaps two stretchers; but it will be seen that, as the length of each brick is exactly twice its width, every alternate vertical joint coincides throughout the whole depth of the wall, which is thus divided into several independent vertical strips or piers, having no bond or connection with one another. This is manifestly a weak and defective arrangement. The remedy for the evil is the use of "closers."
Closers are pieces of brick (ccc, Fig. 20) inserted in alternate courses, in order to prevent two headers from being exactly over each stretcher, and thus to obtain a lap.
Queen closers are bricks cut longitudinally in half, or specially made of the size and shape of half a brick. They are inserted next to the last bricks at the angles of the wall, in alternate courses, as at c c c, Fig. 20, and being each only half the width of a brick (i.e. 2 1/4 inches), have the effect of causing every brick in these courses to be placed 2 1/4 inches farther from the corner than it is in Fig. 19. The bricks of the intermediate courses remain in the position shown in that figure, and the consequence is that the vertical joints of the courses containing closers, instead of coinciding with those of the courses above and below, are 2 1/4 inches beyond them in every case, and thus straight vertical joints are avoided.
Closers should, if possible, be arranged so as to extend right through the thickness of the wall.
As it is not easy to cut a brick longitudinally in half without breaking it, it is frequently cut into quarters, each of which is a half closer, and two placed end to end form a queen closer.
being left on, strengthens the work considerably, and is a great advantage in some situations, such, for example, as that shown in Fig. 105 (see p. 33).
Three-quarter bats are sometimes used instead of closers, If so, they should be placed at the extreme end of the wall, so as to form the quoin bricks of the stretching courses, as at b b b in Fig. 22.
They may, however, be used in the same position in the heading courses, and for all thicknesses of walls either in English or Flemish bond. The use of 3/4 headers is expensive and wasteful, for each of them spoils a whole brick, the piece cut off being useless; whereas, with ordinary closers, every bit of brick may be used up.
Fig. 20. Wall with Queen Closers.
Fig. 22. Wall with 3/4 Bats.