WEIGHT OF ROOF COVERING 9 



In estimating the weight of corrugated steel allow about 25 per cent 

 for laps where two corrugations side lap and 6 inches end lap are re- 

 quired, and about 15 per cent for laps where one corrugation side lap 

 and 4 inches end lap are required. Nos. 20 and 22 corrugated steel 

 are commonly used on the roof and Nos. 22 'and 24 on the sides. 



Weight of Roof Covering. The approximate weight per square 

 foot of various roof coverings is given in the following table : 



Corrugated iron, without sheathing i to 3 Ibs. 



Felt and asphalt, without sheathing 2 



Felt and gravel, without sheathing 8 to 10 



Slate, 3-16" to %", without sheathing 7 to 9 " 



Tin, without sheathing I to 1^/2 " 



Skylight glass, 3-16" to l / 2 ", including frames 4 to 10 



White pine sheathing i" thick 3 



Yellow pine sheathing i" thick 4 



Tiles, flat 15 to 20 



Tiles, corrugated 8 lo 10 



Tiles, on concrete slabs 30 to 35 



Plastered ceiling 10 



For additional data on weight of roof coverings, see Chapter XIX. 



The actual weight of roof coverings should be calculated if possible. 



Weight of the Structure. The weight of the roof can now be 



found. The weight of the steel in the sides and ends is approximately 



the same per square foot as the steel work in the roof. 



A very close approximation to the weight of the steel in the en- 

 tire structure where no sheathing is used and the same weight of cor- 

 rugated iron is used on sides as on roof, may be found as follows: 

 Take the sum of the horizontal projection of the roof and the net sur- 

 face of the sides and ends, after subtracting one-half of the area of the 

 windows, wooden doors and clear openings ; multiply the sum of these 

 areas by the weight per square foot of the horizontal projection of the 

 roof, and the product will be the approximate weight of the 'steel in 

 the structure. 



