For interior finish, scagliola, or imitation marble, is used to some extent for columns, dadoes, etc. This is made upon a ground of lime mortar containing a large proportion of lime and hair. When this groundwork is thoroughly dry, it is covered with a coat of Keene's cement on plaster of Paris, which is mixed with the various colors and polished until it resembles marble. For flat surfaces, this is sometimes made in slabs upon plate glass. Silk threads, dipped in a thin solution of plaster of Paris, colored to imitate the veining, are arranged upon the glass, and the body color put on over them. The silk threads are then withdrawn, and a backing of plaster of Paris and cement, with a webbing of canvas, is spread to the desired thickness. The slabs, when hard and dry, may be taken from the glass and polished in the same manner as genuine marble. When scagliola is skillfully made and polished, its resemblance to genuine marble is almost perfect.

Window Frames

It has been the custom to make the window frames and sashes of a fireproof building of wood, in the same manner as for ordinary city buildings, depending upon shutters of tinned wood or metal construction for protection from external fires. Later developments of fireproof construction, and the disastrous effects of fires in the vicinity of many so-called fireproof buildings, have led to the growing use of metal for all external parts. Several patented forms of metal frames and sashes have been introduced, among which are some made of wood and covered with metal, as shown in Fig. 243, and others entirely of metal, as in Fig. 244. These windows are arranged to close automatically, and, when glazed with wire glass or with small lights of prismatic glass in metal bars, form a filling which is acceptable to most of the insurance exchanges as fireproof.

Fig. 343. Fireproof Window.

Fig. 343. Fireproof Window.

Fig. 244. Fireproof Window.

Fig. 244. Fireproof Window.

This form of glazing is of course not adaptable to show windows and large store lights, but as the upper stories are subjected to the greater danger from fire in adjoining buildings, this defect is not serious.

Interior Finish

While wood is in general use for interior finishing, it is now possible to obtain inside doors and finish made or covered with metal. These doors are usually made of thin sheet metal over a core of pine, and they may be plain or moulded to resemble wooden doors.

Stairs

The stairs of a high building are rarely used above the lower stories, except for emergency, or at times when the elevators are not running; so it is the custom to make staircases simple in design and construction, except perhaps the lower flights, which are often made of marble or of ornamental iron or steel. A simple form of stair construction, and one in general use, consists of a plain cast-iron stringer with cast-iron riser and marble or mosaic treads. (Fig. 245.) The outside stringer may be more or less ornamental, and the soffit or under side of the flight should be neat and presentable, as it will be in close view when passing down the flight underneath. The stairs should be arranged so that the stringers will not be too long to be of cast iron, if desired; but sometimes a steel beam or channel is used with the forming for the steps bolted on, as in Fig. 246. In either case, the bottom-and top of the stringers must be securely fastened to the floor beams. Sometimes the stairs will be laid out to enclose one or more elevators in the well room, and in this case a support for the stringers may be obtained by the corner posts of the elevator enclosure, which, in turn, will be strengthened by the lateral support of the stairs.

Fig. 245. Cast iron Stair Stringers and Finish.

Fig. 245. Cast-iron Stair Stringers and Finish.