CONVICT LABOR FOE ROAD WORK. 
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-annealed 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 2'J ounces per square foot to the 
weights given. 
United States standard gauge for sheet iron or steel. 
No. of gauge. 
Approxi- 
mate 
thickness 
in frac- 
tions of 
an inch. 
Weight 
per square 
foot in 
ounces. 
No. of gauge. 
Approxi- 
mate 
thickness 
fn frac- 
tions of 
an inch. 
Weight 
per 
square 
foot in 
ounces. 
16 
V s 
i* 
40 
36 
32 
28 
24 
22 
20 
23 
8 
shs 
rihr 
■fas 
18 
17 
24 
16 
18 
25 
14 
19 
26 
12 
20 
27 
11 
21 
28 
10 
22 
• 
The sheets generally used have corrugations measuring 2\ 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 be given to roofs that are to be 
covered with corrugated sheets is 3 inches to the foot, and the 
sheets, as laid on the roof, should have a lap at the lower end of 
53577°— Bull. 414—16 10 
