This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
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 backing, and often the face as well, will 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.
Fig. 104. Sidewalk Beams.
The advantages of bricks over stone are that they are practically indestructible, either from the action of fire or the elements; they are less expensive and more easily handled. Good building bricks of their respective kinds should be sound and free from flaws and stones or lumps of lime, uniform in size, and square, hard and not too absorbent. A 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.
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 be fixed by law, 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 walls in general, for a building of five stories, should not be 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.