It is necessary to see that the drawings are ac curately followed, and the work properly assembled, that the quality of work is up to the standard, riveted tightly and accu rately done. The mem bers must be straight and free from twists or bends, punching sharp and true, with the holes in the dif ferent pieces exactly op posite. Column ends and all bearing surfaces true and at right angles to the axis. All portions not accessible after put ting together must be painted before being as sembled.
Cover= ing. The adaptability of terra cotta to the terior adornment and fireproofing of buildings is so great that its use has become general in all places where durability and resistance to heat are essential. The ornamental facings can not always be ported by direct bearing on the steel frame, and so a system of anchors and ties must be devised by which the separate blocks may be held in place.
For terra-cotta finish which has no great projection from the line of support, ties of one-quarter inch rods may be hooked into the ribs of the terra cotta and secured to the steel frame or the brick filling, as in Fig. 230, but when a greater projection is required, as for cornices, small beams or T-irons must be used, well built in or anchored to the main structure, as in Fig. 231. Exterior terra cotta as ordinarily finished is not affected by the atmospheric conditions which affect stone; but as the surfaces arc liable to become warped in the baking, it will be necessary to see that no attempt is made to straighten bad pieces by chiselling, as this destroys the surface and exposes the softer interior to decay.
Fireproofing. We have thus far considered the covering of the steel skeleton from the point of obtaining an available floor surface, and the necessary housing in by means of the exterior walls. While these elements are also made to serve their turn in protecting the frame from fire and the elements, further and complete protection from fire must be considered as of prime importance.
Columns. Especially is this true in the case of the columns, which necessarily sustain a great weight, and should therefore be adequately protected. Columns may be enclosed in brick, which should be not less than eight inches thick, or hollow terra-cotta tiles may be used, preferably in two layers, each not less than two inches thick and breaking joints. (Fig. 232.) Columns may also be pro
tected by the use of metal lathing and plaster in one or two layers with an air space between. (Fig. 233.) Girders. While the floor beams and flush girders are pro tected normally by the floor or ceiling construction, girders which drop below the floor must be given a special protection. This may be of porous terra-cotta blocks, shown in Fig. 234, or of metal lathing and plaster, Fig. 23:i.
The makers of floor construction have each their own system of fireproofing of girders and columns and other exposed members, and, in general, the contractor for the floors will be given a contract for all the other fireproofing of the building.
Partitions. The partitions of fireproof buildings may be built of brick, terra-cotta, tiles, or plaster blocks, or of light iron studding with metal lathing and plaster. Brick partitions, to resist the passage of fire, must he at least twelve inches thick, and so are not generally used unless required for floor bearing also. With the column and girder construction which we have had under a Iighter construction than brick is generally desired for partitions.
Partition Blocks. Terra-cotta blocks, either of dense or porous terra cotta, make a. very good partition; these are usually made four inches thick, and are of the same composition as the floor blocks. They are usually set with the hollows running horizontally, in order to obtain the flat surface for bedding, but where it is necessary to cut for vertical pipes, it is well to set a vertical line of blocks on end and clamp them to the flat tiles. All openings for doors and windows are framed with wooden studs (or with steel bars, if the door frames are of cast iron) to receive the frames and finish. (Fig. 236.) For thinner partitions, blocks of solid porous terra cotta two inches thick may he used, but they must be clamped or banded together. A patented partition may be obtained of thin terra-cotta plates reinforced by twisted steel wires run on either side of the plates and embedded in the plaster. Thin plates having piaster of Paris for a base, and clamped or banded with iron, are also used for partition blocks where extra lightness is required.