"Mortar is sometimes made so thin that the brick will not absorb all the tiyatee. This practice is objectionable; it interferes with the setting of the mortar, and particularly with the adhesion of the mortar to the brick. Watery mortar also contracts exces sively in drying (if it ever does dry), which causes undue settlement and, possibly, cracks or distortion. The bricks should not be wetted to the point of saturation, or they will be incapable of absorbing any of the moisture from the mortar, ;tnd the adhesion between the ]brick and mortar will be weak. The common method of wetting brick by throwing water from buckets or spraying with a hose over large pile is deceptive, the water reaches a few bricks on one or more sides and escapes many. Immersion of the brick for from three to eight minutes, tes, depending upon its quality, is the only sure method to avert the evil consequences of using dry or partially wetted brick. Strict attention must be pail to have the starting course level, for the bricks being of equal thickness throughout, the slightest irregu hirity or incorrectness in it will he carried into the superposed courses, and can only be rectified by using a greater or less quantity of mor tar in one part or another, a course which is injurious to the work. A common but improper method of building thick brick walls is to lay up the outer stretcher courses between the header courses, and then to throw mortar into the trough thus formed, making it semi 1111ie1 by the addition of a large dose of water, then throwing in the brickbats (sand and rubbish are often substituted for bricks), allowing them to find their own hearing; when the trough is filled, it. is plastered over with stiff mortar, and the header course laid and the operation repeated. This practice may have some advan tage in celerity in executing work, lint none in strength or security." A modification of this practice, where the bricks are laid ilry and grouter] with moderately thin mortar la every coarse, may be successfully used in weather when there is no danger of freezing, mid will make solid work. This is especially so for footings and foundations of brick where it is necessary that every joint shall be filled, as the thin grouting is more to be depended upon to fill every joint than the average mason.
Joints. For inside walls which are to he plastered or other wise concealed, the joints may be simply cut oft flush with the trowel, but where the walls arc exposed, the joints should be "struck." (Fig. 10:i.) This consists in pressing or striking back with the trowel, the upper portion of the joint while the mortar is soft, so as to form a sloping surface from the bottom to the top. "heyed joints" are formed by running an iron jointer with round or V-shaped edge along the center of the flush joint, giving it a depression and hardening the mortar by the pressure. (Fig. 106.) Ruled joints are made by holding a straight-edge ender the joint and running the Jointer along, making a derfectly straight joint.
Bonding. The strength of a brick wall depends not only upon the bricks, the mortar, and the workmanship, but the assembling of the different members, the bond or arrangement adopted for tying together the separate parts, and also for distributing the effects of concentrated loading. The common bonding consists of laving even- fifth or sixth course of bricks at right angles to the direction of the wall, as in Fig. 107. 'These courses are called header courses and serve to tie the wall together. Where the wall is faced with pressed brick and the regular occurrence of header courses would not look \veil, the face work is tied to the backing by clipping off the back corners the face bricks, and inserting a course of (hag omal headers. (Fig. LOS.) Galvanized steel ties of patented manu facture are extensively used in the East and are effective for this purpose. English bond is a bonding much used in England and consists of alternate courses of headers and stretchers, as in Fig. 109.
Flemish bond, Fig. 110, consists of alternate headers and stretchers in each course. This bond is sometimes used effectively in facings of common brick, by using blackened headers, and it is sometimes used for every fifth course of face work instead of the diagonal headers. The bonding of angles is an important matter, and, ill addition to the regular bond, most of the city laws require that the corners shall be tied with iron straps or bolts. In joining new work to old, how ever, direct bonding should be avoided for tear of unequal settlement, and some such method as shown in Fig. 111 5110111(1 be adopted.
hollow Walls. To overcome the tendency of a solid brick wall to transmit heat, cold, or dampness, hollow walls are often used. A given number of bricks, if built as a hollow wall, will make a more stable wall than a solid wall built from the same number; besides the gain of the air space. Nearly all building laws require the same amount of brickwork, independently of the air space, in hollow walls, as is required in solid walls, so that there is a loss of space which must be considered in city building.
An important consideration is the bonding of the two portions of a hollow wall so that each shall help sustain the other. The usual method has been to do this liv means of withes or headers of brick extending across the air space, as in Fig. 112, but these permit the moisture to pass from the outer to the inner shell, and also allow the mortar dropped from the higher portions of the wall to collect and partially fill the space; a more effective method of bonding is by means of a metal tie, either of steel wire or of Iron, and these should be made cVith a dip in the center to allow any moisture which may conic from the outer wall to drop off and not communicate with the inner wall. (Fig. 113.) These ties should be either galvanized or clipped in hot asphalt. It is a good plan to provide fora circulation of air through the space between the walls, by leaving openings in the basement and in the where possible. Hollow bricks are sometimes used for the inside course of exterior walls, but, while they are par tially effective in excluding moisture, they do not fill the place of a hollow wall Common Bricks. We have made free mention of " face bricks," etc. Let us pause to consider just what is meant by the terms. Com mon bricks include all rough unpressed bricks which have had no special care taken in their manufacture. These, according to their position in the kiln, become burned to varying degrees of hardness. "larch brick" are those which, from being near fire, become burned to a great degree of hardness and are often warped, vitreous, brittle, and weak. "Red bricks" are those which are burned with an even and moderate temper ature and compose the bulk of the kiln. Salmon, or soft bricks are those which are found at the top of the kiln and are usually under burnt. They are good only for inside courses and for lining chimneys. Face bricks, in which general terra are included pressed bricks, moulded bricks, etc., are made or re-pressed in a dry press machine. Face bricks are more expensive to Ilse than common bricks and are generally used for facing exterior walls, for fireplaces, and for work."Enameled bricks" are bricks whose face is covered with a coat of enamel of selected color. The true enameled brick is a Yen expensive article, so that most of the bricks called by this name are glazed bricks, the difference being that the true enamel is fused into the clay and is opaque in itself, while the glaze is formed by coating the surface with a. colored film and covering this with the transparent glazing. This film is apparent on chipping off the glazing, while the true enamel shows no line between the body of the brick and the surface.