Oil canning is a common issue in PVC roofing and metal panel installations, where large flat surfaces show visible waviness or slight buckling that looks like ripples or dents. It’s caused primarily by thermal movement, uneven tension during installation, or substrate irregularities. PVC roofing membranes and panels expand and contract with temperature changes, and if the material isn’t properly secured or is installed over an uneven surface, this movement can create those unsightly waves. Sometimes, oil canning occurs because of over-tightening fasteners or improper panel alignment, which leads to tension imbalances. Simple DIY checks include inspecting for loose fasteners, ensuring panels or membranes lie flat without gaps, and looking under the edges for uneven substrate or debris that might push the material upward.
If you notice persistent waviness or buckling, it’s a good idea to call a professional roofer to assess the situation. They can check for structural issues, such as warped decking, improper fastening techniques, or whether thermal expansion joints are correctly installed. When talking to a contractor, ask if the panels or membranes were installed with adequate expansion space and whether fasteners were uniformly tightened without over-torquing. Also, check what methods they use to ensure the substrate is smooth and stable before installation. These questions help ensure the roofer understands the causes of oil canning and is prepared to fix it without compromising your roof’s warranty or long-term performance.