Gallery floors in churches and theatres are generally supported by the wall of the building at the outer end, and by columns and girders at the inner end. The floor is generally stepped for each row of seats, and the front of the gallery usually projects 3 feet or more beyond the face of the girder.
Theatres. - The proper planning of the galleries in a theatre or opera house is a matter that requires considerable study, but as the author purposes to treat only of the framing, he would refer the reader to Mr. William H. Birkmire's recent book on "The Planning and Construction of American Theatres"* for methods of laying out the inclination of the galleries in such buildings.
* John Wiley & Sons, Publishers. Price, $3.
In the better class of theatres the construction of the balcony and galleries is usually entirely of steel. The following examples of gallery construction, taken from Mr. Birkmire's book, will serve to illustrate the usual method of framing. Fig. 458 shows the construction of the balconies in Abbey's Theatre, New York, Messrs. J. B. McElfatrick & Son, architects.
"For the support of the steppings in this theatre there are 8-inch steel channels extending from a line of 12-inch beam girders between the back columns to the inner circle lattice girders, and projecting nearly 10 feet beyond the girder. The channels are placed about 2 feet 6 inches apart and radiate toward the point from which the steppings are described.
"The steps are constructed of 1-inch yellow pine flooring upon
2-inch battens secured to stepping pieces of 1 ½x1 ½-inch steel angles, bolted to the radiating channels.
"The risers are made of sheet iron about 1/16 of an inch thick and also secured to the angles."
The ceiling beneath was formed by bolting 1¼ x1 ¼-inch angles to the under side of the channels every 16 inches, and on these wire lathing was secured.
"The front of the balcony is constructed of 3 inch channel posts placed about 4 feet apart and secured to a continuous 6 inch channel extending around the entire front."
In the Empire Theatre, by the same architects, the steppings are supported by small lattice trusses (Fig. 459) which also radiate to the point from which the steppings are described. Between the trusses, and resting upon the bottom chord, Guastavino arches are constructed, making an excellent and practical fireproof ceiling, doing away with all furring and making desirable curves for the decorations.
"To support the flooring, which is of 2-inch boarding, knee pieces of plates and angles are secured to the top chord of each truss, as shown in the illustration. At the top of each knee piece 2-inch channels, and at the bottom 2-inch angles are secured, extending in a circle the entire length of the galleries."
The risers, as in the previous example, are of plate iron.
Another favorite method of constructing these galleries is to use steel beams, placed about 4 feet 6 inches apart, and filled in between with fireproof arches of brick or hollow tile.
"This is no doubt the cheapest form, but the top and bottom of the beams are required to be bent to conform to the girders and step-pings of the tiers. If the girders supporting the lower ends of these beams are level the bending is an easy task, but when the front rakes 2 or 3 feet the beams become of different lengths, and then different bends are required. This construction is also considerably heavier than the Guastavino arch system and requires more metal in the beams and columns."