GENERAL RULES FOR BUILDING BRICK MASONRY.
1. Reject all misshapen and unsound bricks.
2. Cleanse the surface of each brick, and wet it thoroughly before laying it, in order that it may not absorb the moisture of the mortar too quickly.
3. Place the beds of the courses perpendicular, or as nearly perpendicular as possible, to the direction of the pressure which they have to bear; and make the bricks in each course break joint with those of the courses above and below by overlapping to the extent of from one-quarter to one-half of the length of a brick. (For the style of bond used in brick masonry, see under Bond in list of definitions.) 4. Fill every joint thoroughly with mortar.
Brick should not be merely laid, but every one should be rubbed and pressed down in such a manner as to force the mortar into the pores of the bricks and produce the maximum adhesion; with quick setting cement, this is still more important than with lime mortar. For the best work it is specified that the brick shall be laid with a "shove joint," that is, that the brick shall first be laid so as to project over the one below, and be pressed into the mortar, and then be shoved into its final position.
Bricks should be laid in full beds of mortar, filling end and side joints in one operation. This operation is simple and easy with skilful masons—if they will do it—but it requires persistence to get it accomplished. Masons have a habit of laying brick in a bed of mortar, leaving the vertical joints to take care of themselves, throwing a little mortar over the top beds and giving a sweep with the trowel which more or less disguises the open joint below. They also have a way after mortar has been sufficiently applied to the top bed of brick to draw the point of their trowel through it, making an open channel with only a sharp ridge of mortar on each side (and generally throwing some of it overboard), so that if the succeeding brick is taken up it will show a clear hollow, free from mortar through the bed. This enables them to bed the next brick with more facility and avoid pressure upon it to obtain the requisite thickness of joint.
With ordinary interior work a common practice is to lay brick with and i-inch mortar joints; an inspector whose duty is to keep joints down to f ors inch will not have an enviable task.
Neglect in wetting the brick before use is the cause of most of the failures of brickwork. Bricks have a great avidity for water, and if the mortar is stiff and the bricks dry, they will absorb the water so rapidly that the mortar will not set properly, and will crumble in the fingers when dry. Mortar is sometimes made so thin that the brick will not absorb all the water. 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 excessively in drying (if it ever does dry), which causes undue settle ment 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, and 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 a large pile is deceptive, the water reaches a few brick on one or more sides and escapes many. Immersion of the brick for from 3 to 8 minutes, 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 paid to have the starting course level, for the. brick being of equal thickness throughout, the slightest irregularity or incorrectness in it will be carried into the superposed courses, and can only be rectified by using a greater or less quantity of mortar 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-fluid by the addition of a large dose of water, then throwing in the brick (bats, sand, and rubbish are often substituted for bricks), allowing them to find their own bearing; 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 advantage in celerity in executing work, but none in strength or security.