32 BULLETIN 801, U. S. DEPARTMENT OE AGRICULTURE. 
G inches in 50 feet, the usual amount for the compartment 100 feet in 
length between exterior walls. This slope will reduce damage to the 
cotton and, in the case of elevated floors, will prevent possible over- 
loading from an accumulation of water — such as might result from 
continued flow of sprinklers. 
ROOF AND SELF-SUPPORTING FLOORS. 
Designs and materials for fire-resistive roofs and self-supporting 
floors have been tried in many forms. Many methods of construction 
used in the early development of fire-resistive construction were 
needlessly costly and afforded very poor protection. In fact, the 
simplest and often comparatively inexpensive construction usually 
has proven the best. 1 This discussion of roof and floor designs will 
be confined to constructions which is most suitable for the warehouse. 
For special conditions other types of construction possibly may be 
suitable. 
Reinforced concrete is preeminently suited for the requirements 
of the cotton warehouse. This material consists of concrete com- 
posed of Portland cement, sand, and crushed stone or similar ma- 
terial, so strengthened or reinforced with steel rods as to secure the 
most economical use of the strength and fire-resistive qualities of 
both materials. 2 
In this construction the tensile strength, or the capability to with- 
stand a pulling force, is supplied by the steel rods which are pro- 
tected, from the action of fire by the surrounding concrete. The 
compressive strength, or the capability to withstand a pushing 
force, is supplied by the concrete. This action of the concrete is 
sometimes supplemented by additional steel. The value of this con- 
struction depends very largely on a proper proportionment and ar- 
rangement of the concrete and the steel. A detailed discussion of 
the engineering phase of the construction is scarcely within the 
scope of this treatise, though it should be pointed out emphatically 
that the design should be handled by a competent engineer experi- 
enced in this character of work, while the construction should be 
under careful supervision. The most dangerous construction has 
been the result of builders having no knowledge of the real principles 
of engineering involved. The mere judgment of such builders is 
worthless in this type of construction, even though they may be 
successful in ordinary frame buildings. 
*&* 
1 Valuable information and result of fire tests is contained in a Report on a 
Test of Floors in the United States, by Ira H. Woolson, E. M., consulting engi- 
neer, National Board of Fire Underwriters and Rudolph P. Miller, C. E., 
superintendent of buildings, New York City. 
2 See U. S. Bureau of Standards, Technologic Paper No. 2 : The Strength 
of Reinforced Concrete Beams; Results of Tests of 33S Beams, by Richard 
L. Humphrey and Louis H. Losse, 1911. 
