CONVICT LABOR FOE KOAD WOEK. 



143 



CORRUGATED IRON AND STEEL SHEETS. 



Corrugated sheets of iron and steel, usually galvanized, are used 

 frequently for roofing convict camps. The best grades are made 

 of double-refined box-amiealed iron or steel. The weight and thick- 

 ness of the metal from which the corrugated sheets are rolled is 

 represented by gauge numbers based on standard gauges established 

 by act of Congress and known as United States standard gauge'. 



The following table gives the weights and thicknesses of the dif- 

 ferent gauges from No. 16 to No. 28, between which limits are 

 included practically all the weights useful for ordinary roofing. 

 Galvanizing the sheets adds about 2h ounces per square foot to the 

 weights given. 



United States standard gauge for sheet iron or steel. 



No. of gauge. 



16 

 17 

 18 

 19 

 20 

 21 

 22 



Approxi- 

 mate 



thickness 

 ia frac- 

 tions of 



an inch. 



Weight 



per square 



foot ia 



No. of gauge. 



23 



24 

 25 

 26 

 27 



28 



Approxi- 

 mate 

 thickness 

 fn trac- 

 tions of 

 an inch. 



TSTJ 



Weight 



per 

 square 

 foot in 

 ounces. 



The sheets generally used have corrugations measuring 2J inches 

 from center to center. They are made in all gauges from No, 16 to 

 No. 28, and are carried in stock in 4, 5, 6, 7, 8, 9, and 10 foot lengths, 

 and can be obtained as long as. 12 feet at a cost of 5 per cent extra 

 per foot. The 8-foot length is most commonly used. The width 

 of the sheets, as a rule, is 24 inches between the centers of the 

 outer corrugations. All sheets are sold by the square (100 square 

 feet), measuring the actual widths and lengths of the corrugated 

 sheets. 



The thickness or gauge required depends upon the distance between 

 the supports on which the sheets are laid. The maximum distances 

 between supports for the various gauges should be as follows : 



For No. 26 to 28 gauge, from 1 to 2 feet, center to center. 



For No. 24 gauge, from 2 to 2| feet, center to center. 



For No. 22 and 20 gauge, from 2 to 3 feet, center to center. 



For No. 18 gauge, from 4 to 5 feet, center to center. 



For No. 16 gauge, 5 to 6 feet, center to center. 



The least pitch which should 1)0 given to roofs that are to be 

 covered with corrugated sheets is 3 inches to th(^ foot, and the 

 sheets, as laid on the roof, should have a lap at the lower end of 

 53577"— Bull. 414—10 10 



