144 
BULLETIN 414, U. S. DEPARTMENT OE AGRICULTURE. 
from 3 to 6 inches, the larger laps being used on the lower pitches. 
For the side lap it is recommended that each alternate sheet be laid 
upside down and lapped as shown in (a) rather than (b), figure 9. By 
this method, when water is blown through the first lap, it will stop 
and not pass the half lap, but run down and out at the end of the 
sheet. 
In applying to the sheathing or wooden strips, the sheets should be 
secured by nailing through the tops of the corrugations, the nails 
being driven through every alternate corrugation at the ends and 
about 8 inches apart at the sides. 
In ordering corrugated sheets an allowance must be made for the 
laps. The following table (17) gives the number of square feet 
Fig. 9.— Proper (a) and improper (b) manner of laying corrugated roofing. 
necessary to cover 100 square feet of actual surface, using sheets 8 
feet long. If shorter sheets are used, the allowance must be slightly 
increased. 
Table 17. — Number of square feet of corrugated sheets to cover 100 square feet of roof . 
End laps. 
1 inch. 
2 inches. 
3 inches. 
4 inches. 
5 inches. 
Square 
feet. 
Square. 
Square 
feet. 
Square 
Square 
feet. 
feet. 
fat. 
110 
Ill 
112 
113 
114 
116 
117 
118 
119 
120 
123 
124 
125 
126 
127 
6 inches. 
Side lap, one corrugation 
Side lap, one and one-half corrugations. 
Side lap, two corrugations 
Square 
feet. 
115 
121 
128 
Cement Concrete. 
Portland cement concrete may be used in a convict camp for vari- 
ous purposes, such as the construction of floors, building foundations, 
well casings, and protective coverings, etc. Necessary information 
