What does double coverage mean in asphalt roofing?

• A. A technique for building a double-height roof.
• B. A method of installing two decks on top of each other.
• C. The overlapped portion is at least 2 inches wider than the exposed portion, resulting in two layers over the deck.
• D. A type of shingle with two rows of tabs.

Answer: (C)

Double coverage describes a roofing setup where each area over the deck is covered by two layers of shingles. This happens when the part of the shingle that is overlapped by the next course is at least 2 inches wider than the part that remains exposed. In other words, the overlap is intentionally larger so two shingles lay over the same spot, giving extra protection against water intrusion and wind uplift. It’s not about building a double-height roof, stacking two decks, or using a shingle with two rows of tabs—the idea is the deliberate, wider overlap that creates two layers over the deck.