CONSTRUCTION AND FIRE PROTECTION OF COTTON WAREHOUSES. 47 
The variety of material and construction is usually limited to those, 
adapted to roofs of very slight pitch since this slight incline is pre- 
eminent for warehouse designs. That the roofing material should be 
non-inflammable is of even greater importance for this construction 
than for the fire-resistive. In the case of a concrete slab the dan- 
ger would be limited to access of sparks through ventilators and sky- 
lights and all fire damage would be confined to the possible loss of 
the roofing material. On the contrary, for slow-burning construc- 
tion, the roofing material itself must serve as a protection to the 
roof planking against exterior fire. Furthermore, the roofing is 
called upon to resist the lifting, or " sucking," action of wind and, 
therefore, must have either considerable strength or weight or both. 
There are certain elements peculiar to a fire in a cotton warehouse 
which render unsuitable for roofing some materials, such as tin and 
sheet iron, which are well suited to other purposes. It is true that 
these materials are proof against spark hazard from external sources, 
but they present a serious handicap to the extinguishment of fire 
which has originated in or gained access to an individual compart- 
ment. Some critics hold that the chief objection to tin or sheet iron 
is that when the supporting framing is burned away the metal falls 
upon the cotton and prevents effective application of water with a 
consequent heavy loss of the cotton. Others hold that it is better in 
case of fire that a hole be burned through the roof so as to permit the 
direct escape of heat and smoke in order that all openings may be used 
more readily for application of water. Such action is retarded when 
the burning framing with metal clinging to it falls bodily on the cot- 
ton. The composition roofings, on the other hand, break up under 
such conditions and do not present any material hazard. Certainly 
the feature of salvage from a cotton fire is sufficient to make the use 
of metal roofings inadvisable unless applied over 2 -inch planking, 
that the corners of timbers be beveled or chamfered, but in any event splinters 
on corners should be removed as these afford ready facility to ignition. 
The wearing or surface floor should be laid diagonally or at right angles to 
the heavy floor plank. The surface tloor may be pine, though a hardwood such 
as maple should be used where much trucking is contemplated. 
The waterproof paper should be turned up at wall and columns 6 inches. 
This construction is very desirable for warehouses used by cotton mills where 
fire or water damage may result in a loss greater than the commercial value of 
the cotton because of expense and delay in making replacement with cotton of 
like character. 
The " Regulations of the National Board of Fire Underwriters Governing 
Standard Mill or Slow-Burning Construction" is a concise specification of the 
very best practice. Every engineer and builder should endeavor to follow these 
recommendation which were prepared by the foremost engineers engaged in 
commercial, scientific, and fire-prevention work. 
