Choosing a metal roof means choosing one of the most durable, beautiful, and high-performing roofing systems available. That said, even the best roofing materials have some quirks. For example, a concern sometimes associated with a metal roofing system is the potential for visible “waviness,” which is known as oil canning. This does not indicate a structural problem; it is primarily a cosmetic issue. But it does deserve some thoughtful consideration because a metal roof is a significant investment. With proper design, material selection, and installation practices, this potential issue can be minimized, ensuring customers’ new or retrofitted roofs deliver the lasting beauty metal systems are known for.
Oil canning is a subtle waviness or rippling that can appear on the flat surfaces of metal roofing panels. It is often most visible in direct sunlight, especially in the afternoon when light reflects across the panel surface. Fortunately, oil canning is not a material or structural defect, but primarily a cosmetic issue.
This phenomenon occurs for several reasons. Stresses introduced during coil production, the handling and roll-forming process, pan widths and metal gauge, and deck irregularities can lead to slight panel distortion. Fasteners that are over-tightened may add additional stress to the panel and limit natural movement, which increases the likelihood of oil canning. Because flat sheet metal is susceptible to small distortions when exposed to substrate irregularities or fabrication variances, oil canning should be approached as an expected behavior rather than a defect.
Minimizing oil canning begins with increasing the rigidity of the panel itself. Heavier-gauge metal and reduced panel width help to enhance stiffness, while the addition of ribs and striations add further structure to the panel. Ensuring the roof deck is flat and free of irregularities further prevents the substrate from telegraphing into the finished panel causing unintended buckling. Equally important is avoiding over-tightening fasteners, allowing proper spacing for thermal expansion and contraction. As a final safeguard, choosing a low-gloss finish can reduce glare and reflections, making any remaining waviness far less noticeable.
Oil canning is a cosmetic issue and can be minimized by using heavier-gauge materials, adding ribs or striations, choosing narrower panels, preparing a smooth deck surface, and selecting a low-gloss finish. While no method guarantees the complete elimination of oil canning, combining these best practices greatly reduces its visibility and helps ensure a more uniform appearance across the roof’s surface. When designers, fabricators, contractors, and building owners collaborate, expectations are aligned, and best practices are followed, the result is a high-performance metal roof that delivers long-term satisfaction and stunning curb appeal.
For project-specific assistance or additional technical guidance, contact your local Drexel Metals representative or our technical services team. We’re here to ensure that your metal roofing system not only meets performance standards but exceeds them.
