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 21 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 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 inch to 11 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 capac ities 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 inch, could probably be repaired by hard plas ter, so that, although not being as good as it was originally, the partition, in case of another fire, would still be considered reason ably safe.
The wire lath partitions cannot be considered fireproof until they are plastered. Here, accordingly, the plaster forms au essen tial feature of the partition ; and in case of any considerable portion of this being destroyed and exposing the metal frame, the partition could be repaired by replastering, provided the metal frame had not been injured.
The concrete blocks and the terra cotta blocks in the tests cited above were not injured by the fire and water test ; and so, if the results under actual conditions were always as favorable as in these artificial instances, the expense of repairing this form of par tition would appear to be less than in the case of the other forms. It should be noted, however, that the partitions tested were with out openings, and that openings in a partition weaken its lateral stability. While the block partitions were uninjured, they might not show so favorable results where openings occur, because of the attendant loss of lateral strength. In this respect it is probable that the plaster and wire lath partitions, and those plaster board partitions having metal stiffening, would not be any more liable to failure with openings than without, because, as constructed, the metal frame is secured at floor and ceiling, and, where openings occur, the frame is also tied longitudinally.