Oil canning in asphalt shingles refers to a visible waviness or uneven surface that looks like the shingles are buckling or rippling. This effect happens when shingles have uneven tension during installation, or if they were stored or installed in extreme temperatures that caused them to expand and contract unevenly. Sometimes, shingles with a flatter profile are more prone to this issue, especially if the roof decking has slight imperfections or if shingles were installed over a rough surface. While oil canning isn’t usually a sign of immediate failure or leaks, it can be unsightly and may make the roof more vulnerable to wind damage over time.
To check for oil canning yourself, look at your roof in bright sunlight or from an angle to spot any signs of waviness or buckling in the shingles. Gently press on the affected shingles to see if they feel loose or don’t lay flat, but avoid walking on the roof if you’re unsure about safety. If oil canning is noticeable or worsening, it’s time to call a roofing professional to assess the installation quality, the roof deck condition, and whether any repair or replacement is needed. When contacting a contractor, good questions to ask are: “What can be done to fix or minimize the waviness without voiding my shingle warranty?” and “Do you recommend checking the roof decking for imperfections that might be causing this?” These questions help ensure any solution is lasting and won’t cause future problems.