BRICK MASONRY Joints in Brickwork.—In the construction of brick masonry, it is necessary that the joints between the bricks be filled with mor tar, the purpose of which is to give a firm and even bearing to the bricks, so that the pressure upon them will be uniformly distributed. The mortar should also adhere to the bricks and bind tlheni into a monolithic mass.
While thick joints usually make weaker masonry than those that are thin, it is desirable that the joint be as thin as it can readily be made. When attempts are made at too thin joints, they are apt to be imperfectly filled, and thus weaken the masonry. Joints in wall masonry of common brick, as used in building construction, are usually from ; to inch thick. It is common to specify the thickness of joints by stating the thickness for eight courses of brick. It is frequently required that the thickness of eight courses of brick masonry shall not exceed the thickness of eight courses of dry bricks by more than 2 inches. When pressed bricks are used for the face of a wall, the joints in the face are usually fron s to s inch thick.
Pressed bricks, being smoother, may be laid to thinner joints with good effect. In heavy masonry as sometimes used in engineering work, the joints usually of cement mortar—are often z inch thick.
Mortar for mortar is more extensively used for ordinary brickwork in building construction than any other. Mixtures of lime and cement mortars in about equal quantities are coming largely into use. The cement materially increases the strength of the mortar and its adhesion to the brick, while the smoothness of the lime mortar is maintained. In important struc tures, where considerable strength is needed, it is common to use cement mortar with addition of 10 to 15 per cent of hydrated lime— a mixture which retains the strength of the cement but makes the mortar easier to work, and usually secures better work than would result from the use of cement alone. In engineering work, cement mortar is usually employed, but the mixture of hydrated lime with the cement is rapidly corning into use.
Laying the the construction of a brick wall the two outer courses are first laid, by spreading a bed of mortar where the brick is to be placed, and against the surface of the last brick laid, then shoving the brick horizontally into place so as to squeeze the mortar into the bottom of the vertical joint between the bricks. A bed of mortar is placed between the outside bricks and the filling bricks are shoved and pressed into place. Mortar is then slushed or thrown with some force into the upper part of the vertical joints to fill them completely.
Bricks should be thoroughly wet before being laid, in order to prevent the water being absorbed from the mortar by the brick. Good adhesion cannot be had between mortar and dry, porous bricks.
In finishing joints upon the face of the wall, a flush joint may be made by pressing back the mortar with the flat edge of the trowel. This is usually clone upon interior walls. A weather joint may be made, as shown in Fig. 33, by using the point of the trowel held obliquely.
61. Bond of Brickwork.—Brickwork is always laid in horizontal courses, and lateral bond is secured by several different arrange ments of the brick in the courses.
Common Bond is the bond most commonly used in the United States, for walls of common brick. In this bond, one course of headers is used to four to six courses of stretchers on the face of the %vall, as shown in Fig. :31.
In Flemish Bond (Fig. 35), alternate headers and stretchers are used in each course, each header being placed over the middle of the stretcher in the course below. Sinai] closers are introduced next to the headers at the corners.
English Bond consists of alternate layers of headers and stretchers (Fig. 36). This construction, like the Flemish bond, makes very strong work. English bond in which the alternate courses of stretchers break joints with each other is called Cross English bond.