Quandaries and Queries


According to my study material 4:12 multiplying factor for shingles is 1.054.  The question reads as follows:  A building with a floor plan of 3350 sq. ft. and a roof slope of 4:12 will require _______ bundles of standard asphalt shingles.
Please show me how to find the multiplying factor 1.054 from 4:12 roof slope.
Thanks again.


Hi Larry,

A roof slope of 4:12 means that in a "run" of 12 units there is a "rise" of 4 units as in the diagram below.

The triangle in the diagram ia a right triangle so, by Pythagoras' Theorem,

L2 = 122 + 42 = 114 + 16 = 160

Thus L is the square root of 160 which is 12.6491.

 12.6491/12 = 1.054 and hence the length of L is 1.054 times the run.



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