For alternate courses, which guideline best describes the joint arrangement?

For alternate courses, which guideline best describes the joint arrangement?

• A. There should be no direct alignment
• B. Sidelap must be 1-1/2 inches
• C. Joints must align on every other course
• D. Joints may align on the same course

Answer: (A)

Staggering joints so there is no direct alignment between successive courses is the guideline being tested. When alternate courses are laid, you don’t want a joint of one course to land right over the joint of the course above or below. If joints line up, you get a continuous seam that can become a leak path and weaken wind resistance. By offsetting each course so the joint falls over the field of the shingles rather than over a joint, you distribute the seams, improve waterproofing, and give nails solid material to bite into. The other options don’t address this essential idea of avoiding joint alignment across courses, which is why they aren’t the best guidance for alternate courses.

Staggering joints so there is no direct alignment between successive courses is the guideline being tested. When alternate courses are laid, you don’t want a joint of one course to land right over the joint of the course above or below. If joints line up, you get a continuous seam that can become a leak path and weaken wind resistance. By offsetting each course so the joint falls over the field of the shingles rather than over a joint, you distribute the seams, improve waterproofing, and give nails solid material to bite into. The other options don’t address this essential idea of avoiding joint alignment across courses, which is why they aren’t the best guidance for alternate courses.