What term describes the distance from the lower edge of a top shingle to the upper edge of the shingle two courses below?

What term describes the distance from the lower edge of a top shingle to the upper edge of the shingle two courses below?

• A. Headlap
• B. Toplap
• C. Exposure
• D. Sidelap

Answer: (A)

Headlap is the vertical overlap between successive courses. The distance from the lower edge of the top shingle down to the upper edge of the shingle two courses below is exactly that overlap—the amount the upper course covers the one below to shed water and seal joints. This is different from exposure, which is how much of the shingle you can see after installation, and from sidelap, which refers to horizontal overlap along the roof face. Toplap isn’t the standard term for this measurement here, so the correct term is headlap.

Headlap is the vertical overlap between successive courses. The distance from the lower edge of the top shingle down to the upper edge of the shingle two courses below is exactly that overlap—the amount the upper course covers the one below to shed water and seal joints. This is different from exposure, which is how much of the shingle you can see after installation, and from sidelap, which refers to horizontal overlap along the roof face. Toplap isn’t the standard term for this measurement here, so the correct term is headlap.