by Dirtman » Mon Sep 11, 2006 5:16 am
A 4' x 8' piece of sheeting equals 32 square feet (length in feet x width in feet = square feet).
20' x 26' equals 520 square feet. As there is 32 square feet in a 4' x 8' piece of plywood, divide 520 by 32, which equals 16.25 pieces. You'll need 17 pieces of 4' x 8' sheeting, IF you have a flat roof.
If your roof isn't flat, you'll need more than that.
George