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Roofing
The estimated roof area is 2,818 square feet
or 261.8 square meters or 313.1 square yards.
To have 10% buffer would require 31 roof squares.
By United States standard, the roof will need:
85 bundles of composition shingles (each bundle will cover ~33 ft2)
29 rolls of roll roofing (~36 in × 36 ft for each roll)
8 rolls of #15 felt (~36 in × 144 ft for each roll)
15 rolls of #30 felt (~36 in × 72 ft for each roll)
Roofing
To have 10% buffer would require 25 roof squares.
By United States standard, the roof will need:
67 bundles of composition shingles (each bundle will cover ~33 ft2)
23 rolls of roll roofing (~36 in × 36 ft for each roll)
6 rolls of #15 felt (~36 in × 144 ft for each roll)
12 rolls of #30 felt (~36 in × 72 ft for each roll)