In superintending brickwork, the main things to be observed have been pointed out in connection with the construction. Especial care should be taken to see that the bricks are properly wet, that sufficient mortar, of the proper quality, is used, and that the joints are thoroughly filled. The bonding of the wall must be constantly noticed, especially face work and piers. The work should be measured from time to time and the position of all openings noted. Reveals and jambs should be measured and plumbed, and the leveling of courses carefully watched. At the level of the floors, the bedding of all bearing plates must be watched and the number and position of floor and wall anchors noticed. Recesses and flues should be carefully followed out, and the tying together of hollow walls should be frequent and effective. When work is stopped, the top of the wall should be covered, to prevent rain from washing out the soft mortar in summer, or from entering and freezing in winter; and to obtain the best results, the laying of brick walls should not be attempted in freezing weather.

Fig. 122. Slip Joint.

Fig. 122. Slip Joint.

For the adaptation of brick construction to modern city building, we may conceive the foregoing principles as elements to be applied to the different conditions and uses to which the walls will be put.

Bearing walls are those which carry besides their own weight the weight of floors or roofs which bear upon them. The thickness of these walls must necessarily increase as does the height of the building, and they must also be strong enough to brace the building against lateral forces such as wind pressure, or the vibrations from external or internal sources.

Curtain walls are those built between steel or iron columns, or between piers, and carry no loads except their own weight. Their thickness needs to be only such as to protect the outside of the building and give support to walls above.

Skeleton construction has all walls, as well as other parts of the building, supported by steel or iron columns and beams. In this case the masonry needs to be only of sufficient thickness to protect the building and the frame against the elements, unless these walls are depended upon for stiffening and bracing the building. The exterior walls may be of brick, concrete, terra-cotta, or other fire-resisting material, depending in a measure upon the location, custom, experience of builders, and the influence of union labor in various localities.

In the case of a skeleton frame, the walls of each succeeding story will be supported independently and may be considered as curtain walls. At the present standard prices of materials, a building for ordinary floor loads can be erected eight stories high, with continuous bearing walls of masonry, more cheaply than with piers and curtain walls or skeleton construction. If, however, the extra land area, which the thicker bearing walls will require, is of value enough, it will be economy to use skeleton construction for six or even five-story buildings, depending largely upon the character and location of the building.