Roof Underlayment Calculator
Flat Area =
Calculates the total rolls of felt underlayment needed for a roof. This takes into consideration a 4in side lap and 6in end lap.
-Rise: Roof rise in units of inches per 12 inches. For example, if the gable rises 4 inches for each 12 inches of horizontal run, enter 4.
-Flat Area: Area covered by the roof.
-Underlayment: 15#, 20# or 30# felt underlayment.
-#Rolls: Total rolls of felt.
Calculate the total rolls of felt underlayment needed for a roof that is 8:12 slope using 30 pound underlayment. The square feet of the home, factoring in the overhang, is 1894ft².
-Flat Area: 1894ft²
-Underlayment: 30# (3' x 72')