A new asphalt shingle roof is only as good as its installation. Even premium shingles fail prematurely if installed incorrectly. Here are the most common asphalt shingle installation mistakes and how to avoid them.
1. Improper Nailing. Nails must be placed in the correct location (the nailing strip) and driven straight. Overdriven nails tear through shingles; underdriven nails don’t hold. Too few nails reduce wind resistance. A quality installer knows the exact nail pattern.
2. Skipping Underlayment or Flashing. These hidden components are critical. See our guide on underlayment and flashing for why they can’t be skipped.
3. Inadequate Ventilation. Poor attic ventilation causes heat and moisture buildup that destroys shingles and decking. Ensure your contractor addresses ventilation during installation.
4. Overlaying Instead of Tearing Off. Installing new shingles over old ones hides damage and shortens the new roof’s life. Always insist on a full tear‑off.
5. Incorrect Shingle Alignment and Overlap. Improper stagger patterns or insufficient overlap create leak paths. This is purely a workmanship issue.
6. Reusing Old Flashing. Always replace flashing during a full roof replacement. Reusing old metal invites leaks.
To avoid these mistakes, choose a licensed contractor carefully—see how to choose a licensed installer. For the process where these errors occur, see what to expect during installation. For material choices, see types of shingles. And for maintenance after the job, see maintenance tips.