Roofing Underlayment Coverage Calculator

Field felt or synthetic roll count from roof area, pitch-based single/double coverage, and waste — not ice-and-water shield

Planning / estimating only — starting point, not gospel. Not a permit, not a substitute for the adopted code in your jurisdiction. 2018 IRC §R905.1.1 requires underlayment on asphalt-shingle roofs. Low-slope sections (2:12 to under 4:12) require double underlayment or equivalent double coverage. This tool sizes field underlayment (felt or synthetic) over the entire deck. It does not include self-adhering ice-and-water shield at eaves, valleys, or penetrations — use the ice & water shield calculator for that separate band. Confirm product labels, overlap requirements, and local amendments before you order.
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