BRICKWORK AND CUT STONE.
In the superstructure of a city building of ordinary height, say up to five or six stories, and excepting the so-called skeleton construction, we shall usually find that brickwork forms the greater part of the wall. The face is often finished with stone, either rough or cut, but the hacking, and often the face as well, wi11 usually be constructed of some form of brickwork, so that bricks of some kind or another are probably more extensively used in the construction of city buildings than any other material.
The advantages of bricks over stone are that they are practi cally indestructible, either from the action of fire or the elements; they are fess expensive and more easily handled. Good building bricks of their respective kinds should be sound and free from flaws and stones or pimps of lime, uniform in size, and square, hard and not too al„orhent. good hard brick will ring distinctly when struck by another brick or by a trowel, and it should not absorb more than ten per cent of its weight of water. In selecting bricks from a quantity delivered, the hard and usually darker bricks should be culled for use on the outside of the walls, while the lighter bricks should be used for backing and the inside courses.
Thickness of Walls. No practical rule can be laid down for the thickness of brick walls, as their crushing strength, which is usually the only direct strain applied, is generally, except in the case of small piers, a minor consideration. In all large cities the least thickness of walls will he fixed by hay, walls of mercantile buildings being heavier than those used for living purposes; and in no case is it advisable that party walls should be less than twelve inches thick. Exterior vgalls in general, for a building of five stories, should not he less than twenty inches in the lower story and twelve inches in the upper story. 'These dimensions applying to stories of ordinary height, and spans of not more than twenty-five feet, nor more than twenty-five feet of length without a pier. Walls which contain thirty-three per cent of openings should also be made thicker.
Brick Laying. To perform the operation of erecting a brick building it is necessary to lay the carefully chosen bricks upon each other, with a hell of some kind of mortar between. Ordinary brick
work is laid 111 cotumota white lime mortar, hut for greater strength and durability there is often added a proportion of cement, and for hriek\vork below ground. cement mortar only should be used. The thickness of the jousts will vary from three-sixteenths of an inch to three-eighths of an inch. according to whether the joint is to be con d or male a feature of the work.
The laying of the bricks should be carefully watched, as there is a tendency on the part of many masons to .slight this work. "Bric•ks should not be merely laid, but every one should lie rubbed and pressed clown 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 he 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 skillful if they will do it, but it requires persistence to get it accomplished. Masons have a habit of laying bricks in a bed of mortar, leaving the vertical joints to take care of themselves, throwing a little mortar over the top heels and giving a sweep with the trowel which more or less disguises the open joint below. 'Cher also have a way after mortar has been sufficiently applied to the top bed of brick, to draw the point of their trowel iitrough it, making an open with only a sharp ridge of mor tar 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. Neglect in wetting the brick before use is the cause of many of the failures of brickwork. Bricks have agreat 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.