CONSTRUCTION AND FIRE PROTECTION OF COTTON WAREHOUSES. 43 



111 order to form a complete lire break the division wall in slow- 

 burning construction nmst extend well through and above the roof, 

 this projection usually being 3 f«et. If the roof has a monitor or 

 combustible sln^light within 50 feet of tlie wall, the X'>arapet should 

 ext<ind to the level of the top of such structure. Moreover, the ends 

 of this wall must project through the eaves or cornice of the roof in 

 the event that sucli combustible material overhangs the exterior wall, 

 This is shown by the drawing in figure 17. The portion of the wall 

 projecting above the roof, or that extending above the bottom of the 

 roof timbers, is known as a '^parapet" or "parapet wall," Avhereas 

 the extension of the ends through the cornice may be termed a "cor- 

 beled extension," or "wing wall." Openings in the division wall 

 are quite as undesirable in this design as in fire-resistive construction 

 and when openings are necessary they should be protected in an 

 equally effective manner. 



All parapet walls should be finished on top with a suitable mate- 

 rial to preserve the mortar joints there. This protection is usually 

 supplied by a coping of terra cotta or concrete. Such copings are 

 shown by Plate XXVI ; figure 2 shows a concrete coping and figure 

 3 a terra cotta coping. ' 



THE EXTERIOR WALL. 



The exterior wall should be of the same material and design as 

 described for similar walls of the bearing and curtain tj'pes for fire- 

 resistive construction. The proportions stated there are sufficient 

 to resist the pressure of ordinary windstorms provided the wall is not 

 excessively long, and tall. 



used, a tapering buttress as indicated by the dotted lines mil be cheaper, 

 while the design shown is suitable for brickwork. 



The pilaster, such as is shown by Plate XXVI, figure 3, is of value in sup- 

 porting loads carried by the wall and gives some added stability to tlie wall, 

 particularly if it is tall, but the pilaster is not a satisfactory substitute for 

 the butti-ess in resisting buckling fi'om expansion. 



Walls longer than 200 feet should contain expansion joints at intervals 

 not exceeding 200 feet, and should have these free ends buttressed- 



The parapet height is not figured into the height of the wall for purposes 

 of determining thickness. 



In the rare instances when a panel wall is used, the same principles should 

 be applied to it except that the total thickness and breadth of each pilaster 

 <or, more properly, column) should be, at the bottom, equivalent to one- 

 eighth of this height. At least one beam should be used near the top of the 

 wall, the beam having a depth of 12 inches or more and a breadth eqnal t<) 

 the greatest thickness of the column but not exceeding 24 inches. This broad 

 beam should supply the necessary resistance to buckling from expansion. The 

 thickness of the panel would be subject to the same limitations stated for 

 similar use in the fire-resistive construction. 



Fire walls for one story buildings with a low story height of only 9 feet 

 may be of 12 inch brickwork. 



