How should the second course of three-tab, square-butt shingles be laid?

The second course of three-tab, square-butt shingles should be laid with a strip from which one-half tab has been cut away to achieve proper shingle alignment and weather resistance. This method ensures that the joints between the shingles of the second course are staggered relative to the first course. Utilizing a half-tab cut allows for a more effective overlap, reducing the likelihood of water penetration through the seams and enhancing the overall durability of the roofing system.

This staggered joint is crucial for creating a balanced appearance and maintaining the roof's integrity against wind and rain. If a full strip were used for the second course, or if it began with an uncovered tab, the risk of water pooling and potential leaks increases, compromising the roof’s waterproof barrier. Cutting one-half tab away is a standard practice that reinforces the weatherproofing characteristics of the installation.