# Exact waste factor on paper



## Slyfox (Jun 13, 2008)

Your question sounds more like your a roofer than a diy'r,
there is a sister forum for contractors to use Contractor Talk.


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## jlhaslip (Dec 31, 2009)

There is never any waste on my jobs.
We roll up our cigarettes with the stuff we cut off. Doubles the tar intake. Cheaper than smokes...


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## Yoyizit (Jul 11, 2008)

Justen said:


> . . .if there is 450lf of perimeter, how many shingles will have to be cut.


If I correctly understand your question this may take some back and forth, and maybe a small computer program.

In the simple and unrealistic case of one layer of non-overlapping shingles:

for a square shape 
with 450 lf perimeter 
the area is (450/4)^2 = 12656.25 sf. 
This will take 4218.75 shingles of dimension 1' x 3'.

For a rectangle shape of 1:3 ratio
with 450 lf perimeter
the area is 9492.1875 sf 
and will take 3164.0625 shingles.

How much shingle overlap? 
What other complicating factors are there?

Let's work out one case at a time.


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