193. In case of fire, the columns and girders in a building are naturally more exposed to heat than are other parts of the structure, and, hence, should be most amply protected, as the effect of fire on ironwork is very severe. There are two general methods of protection in common use: one consists in the use of tiling, and the other of concrete held in position by metal lathing, etc. Usually the girder and column protection is accomplished by the use of the same material that forms the floors. As porous tiling is one of the very best fireproof materials known, it is highly recommended for use as a cover for the ironwork. If wire lathing is wrapped around the tiling, the liability of the blocks becoming displaced during a fire is much decreased.

194. Girders

Girders. In (a) and (b), Fig. 93, are represented two common forms of casings for girders which extend below the floorbeams. These are made of solid porous tile; when dense tile are used, it is best to make them hollow, as shown in (c), Fig. 90. The blocks are held in place by clamps or ties, not shown.

Girders are sometimes wrapped with metal lath, upon which the plastering is applied. This subject will be taken up under "Plastering."

195. Columns are usually rendered fireproof by enclosing them in either dense or porous tiling. The former is probably the most used for this purpose, but is not as effective under the action of fire as the porous variety. The pieces are fastened to one another by concealed metal ties, or by wrapping the casing with wire or metal lathing. The casing is set away from the column, around which an air space is thus left.

194 Girders 221

Fig. 93.

Concrete is also used to protect columns, either applied as a solid covering, or as a shell a few inches thick around the pillars, leaving an interior air space. Plaster applied to wire or expanded metal lath is another method of protection, and will be explained under "Plastering."

196. The Chicago building law makes careful provision in regard to fireproofing columns, and its requirements will serve as a guide to proper construction. ' If brick is used as the protective casing, it must be at least 8 inches thick; if tile is used, it must be put on in 2 rings, each at least 2 inches thick for porous terra cotta, or 2 1/2 inches thick for dense hollow tiling. The two thicknesses of tile must break joint, and must be so fastened as to be independent of each other. If the covering is likely to be injured by trucking, etc. - as in a warehouse or store - the lower 5 feet must be cased in hardwood planks or sheet iron.

197. In Fig. 94 is shown the method of arranging solid porous tile around both square and round columns. In each case, a and b represent the first and second layer, respectlvely; c, the wire or expanded metal lathing binding the pieces together; and d, the plastering. In Fig. 95 are shown similar columns, encased in dense hollow tile.

194 Girders 222

Fig. 94.

194 Girders 223

Fig. 95.

198. The space between the column and casing is generally utilized for placing gas and water pipes, electric wiring, etc., but a better method is to provide another passage adjacent to, but independent of, the column. In this way, if there is occasion to repair the pipes, it will not be necessary to displace the column protection, which might not be put back in perfect condition. The plan mentioned is shown in Fig. 96. _______