Not any single system, probably, would be used in all cases even if the designer were to choose without any conditions affecting his selection. Some systems are naturally better adapted than others to certain conditions. Practically there are always a number of considerations affecting the choice. No attempt will be made here to specify to what conditions certain systems are better adapted than others, as this is largely a matter of judgment at the present time. The considerations in general, however, are as follows:

Light or heavy live loads; dead weight of construction, and consequent spacing of beams and span of arches; necessity of lateral stiffness in floor system; possibility of using paneled ceiling, and consequent increase of clear height story between beams; necessity of flush ceiling, and comparative advantage of solid floor system and furred-down ceiling; protection afforded webs and flanges of beams and girders by different systems; possibility of omitting tie rods and a certain amount of steel in some systems; corrosive effects on steel under certain conditions; rapidity of construction, and allowance for final setting of concrete under certain conditions of weather and of heavy loadings; and comparative cost of different systems.

The weights of hollow-tile floor arches and fireproof materials, in pounds per square foot, are given in the following table:

Table XIV. Weights Of Hollow-Tile Floor Arches And Fireproof Materials. End Construction, Flat Arch

Width of Span Between Beams.

Depth of Arch.

Weight per Square Foot.

5

feet to

6

feet.

8

inches.

27

pounds.

6

,,

7

,,

9

,,

29

,,

7

,,

8

,,

10

,,

83

,,

8

,,

9

,,

12

,,

38

,,