Partitions are of terra cotta, wire lath and plaster, and plaster board.

Illustrations of each are given by Plate VI, Figs. 71 to 77. The element of strength does not form a specially important con-sideration here, as the standard forms are all suitable. The higher the partition the thicker should be the blocks or the heavier the metal frame of the partition. Some of the forms are more soundproof than others and probably more fireproof, but the use of any one is generally determined by architectural conditions. The terra cotta blocks come in standard sizes given by the table below, which also gives the dead weight per square foot. The constructions around openings in partitions, for the different types of partition, are also shown by the above-mentioned cuts.

Partitions are never as fireproof as the floor system in a building. If a form of construction could be used which would prevent the spread of fire through partitions, the modern office building would probably be in truth absolutely, instead of merely in name,

CLUB HOUSE OF THE CHICAGO ATHLETIC CLUB, CHICAGO, ILL.

CLUB-HOUSE OF THE CHICAGO ATHLETIC CLUB, CHICAGO, ILL.

The System of Accounts in Use in this Club is Particularly Well Adapted to its Needs fireproof. The great cause of the weakness of fire resistance lies not in the partitions themselves so much as in the fact that openings for doors, windows, flues, etc., have to be made in them. The arrangement in a great many buildings makes it necessary, in order to give light in the corridors, to have a line of windows in the partitions between them and the offices. In addition there are the doors into the corridors, and the doors and sometimes windows in partitions between offices.

ORCHESTRA HALL, CHICAGO, ILL.

ORCHESTRA HALL, CHICAGO, ILL.

D. H. Burnham & Co., Architects, Chicago, 111.

Exterior of Brick and Bedford Stone; Cornice of Terra-Cotta. Completed in September, 1905. On the Left Stands the Railway Exchange Building; on the Right, the Pullman Building.

Fig 71. ROEBLING 4 IN. WIRE LATH SOLID PARTITION

Fig 71. ROEBLING 4 IN. WIRE LATH SOLID PARTITION.

Fig.72 ROEBLING 2IN. WIRE LATH 50LID PARTITION

Fig.72 ROEBLING 2IN. WIRE LATH 50LID PARTITION.

COLUMBIAN PARTITION.

COLUMBIAN PARTITION.

Partitions 050098

As stated under "Building Laws and Specifications," some cities require in buildings of a certain height the use of metal or of fireproof wood for all inside casings and finish, but in the majority of buildings these are not used. Sometimes, also, where plaster and wire lath partitions are used, the plaster does not extend to the floor, and the baseboard has therefore no fireproof protection back of it.

All these features indicate the real elements of weakness in a fireproof partition, and on the extent to which they can be eliminated depends the utility of the partition as a fire barrier. As will be shown later under the paragraphs on tests, there are a number of forms of partition that can be used, which, if without • openings and the other features mentioned above, will form effectual barriers. The extent to which fireproof wood and metal overcome the difficulties will be discussed farther on.

Tests of Partitions. Numerous fire and water tests of partitions have been made by the New York Building Department. The partitions were of four general classes: - (1) plaster blocks; (2) blocks of cinder concrete; (3) wire lath plastered with King's Windsor cement; (4) blocks of terra cotta. The partitions were 2 1/2 inches and 3 inches thick. All were exposed to as nearly the same conditions as possible, which were: - a temperature gradually increasing from 500° to 1,700° during a period of one hour, and then a stream of water applied for 2 1/2 minutes. Fire in no case passed through any of the structures; but in the case of most of the plaster block partitions the blocks were calcined slightly in certain places, and the water had washed portions away to a depth of 1/2 inch to 1 1/4 inches.

The wire lath partitions did not show calcination, but showed to a greater or less extent the effect of the water in the washing away in spots of the browning coat and scratch coat, and, in some instances, in exposure of the lath or metal supports.

The cinder-concrete blocks showed no effect of either fire or water, except that the plaster on the blocks was stripped off.

The terra cotta blocks stood much the same as the concrete, no effect appearing in the partitions themselves, but the plaster being stripped off.

The chief differences, therefore, seemed to appear in the capacities of the various types of partition to withstand the force of water. Those partitions having a harder and less porous structure stood much the best.

From a consideration of the above tests, it will be seen that some forms of partition, under certain conditions of exposure in case of fire, will prove to be more difficult than others to repair, even though they may not entirely fail. Plaster, constituting the finish surface, could not be expected to stand, and does not in a severe fire; the expense, therefore, of this item in the repair would be essentially the same in all forms of partition.

With some of the plaster board partitions in which the blocks were hollow, the calcination and the stream of water broke through the outer shell, leaving the cells exposed. In such cases it would probably be necessary to provide new blocks, as the old ones could not well be repaired. In the solid plaster board blocks the wear, if not more than 3/4 inch, could probably be repaired by hard plaster, so that, although not being as good as it was originally, the partition, in case of another fire, would still be considered reasonably safe.