Can shingles replace tar and gravel on a roof that is flat or with a slight slope?
The building code states that asphalt shingles are not allowed on slopes less than 2 inches of vertical rise for every horizontal foot of run of the rafter. For asphalt shingles installed on slopes of 2:12 to less than 4:12 the shingles must be self-sealing and installed with 2 layers of type 15 felt underlayment. Wood shingles are not permitted on slopes less than 3:12 and wood shakes are not permitted below 4:12.
