LAYING TH! BRICK. Since most bricks have a great avidity for water, it is best to dampen them before laying. If the mortar is stiff and the bricks are dry, the latter absorb the water so rapidly that the mortar does not set properly, and will crumble in the fingers when dry. Neglect in this particular is the cause of most of the failures of brick-work. Since an excess of water in the brick can do no harm, it is best to thoroughly drench them with water before laying. Lime mortar is sometimes made very thin, so that the brick will not absorb all the water. This process interferes 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. Wetting the brick before laying will also remove the dust from the surface, which otherwise would prevent perfect adhesion.
When the very strongest work is desired, as in brick sewers, it is customary to require that the brick shall be immersed in water for 3 to 5 minutes before being laid. Wetting in the pile is not as effec tive as immersion, since in the pile the water is not likely to reach all of the surfaces of all of the bricks. Masons very much dislike to lay wet brick, since the water softens the skin on their fingers and causes it to wear away rapidly. The softer the bricks the more necessary that they should be thoroughly wet when laid. In freezing weather, care should be taken that the water does not form a film of ice on the brick.
The bricks should not be merely laid, but every one should be pressed down in such a manner as to force the mortar into the pores of the brick and produce the maximum adhesion. This is more important and also more difficult to accomplish with cement than with lime mortar. The increased value of the cement mortar can be attained only by bringing the brick and the mortar into close contact; and this is more difficult to do, since cement mortar is not as plastic as that made with lime. The mason is apt either (1) to
butter the edges of the brick, and thus secure a joint that looks well after the brick is laid; or (2) to place insufficient mortar to make a full bed joint of the required thickness, run the point of his trowel through the middle of the mass making an open channel with a sharp ridge of mortar on each side, and then lay the brick upon the top of these two ridges, thus leaving the center of the brick unsup ported. The first method is the one employed with thin joints, which is a reason why they should not be required; the second method is popular because it requires less exertion and is more rapid than fully bedding the brick. • If strength or imperviousness is a matter of any moment, care should be taken to see that the vertical joints are filled solidly full of mortar. This is called slushing the joints. Unless slushing is insisted upon, masons are apt to butter the end joints, lightly bed the brick, throw a little mortar into the top of the vertical joints, and scrape off the excess above the top of the brick, thus leaving the major portion of the vertical joints open; and sometimes little or no attempt is made to fill the vertical joint between adjacent tiers of stretchers, thus leaving also long and high unfilled vertical spaces.
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 pro ject over the one below, both at the end and the side, and be pressed into the mortar, and then be shoved into its final position. Masons are very reluctant to lay brick with a shove joint, partly because it is hard work and partly because many of them have not acquired the art. If brick are not laid with a shove joint, it is highly improbable that the lower part of the vertical joints will be filled with mortar, and consequently the wall will not be as strong or as impervious to water, air and heat as it would otherwise be.