striation
a parallel series of small grooves, channels, or impressions typically within a metal roof panel used to help reduce the potential for oil-canning.
striation: grooves that flatten metal panels and stop them wavy
A striation is a series of shallow, parallel grooves pressed or formed into a metal roof or wall panel, running the length of the panel. These grooves, typically spaced 4 to 6 inches apart and less than 0.1 inches deep, serve a critical structural and visual function: they stiffen the panel and break up the flat surface in a way that makes oil-canning, or visual waviness, much less noticeable to the eye.
Oil-canning occurs when large flat expanses of thin metal move subtly under thermal stress, wind load, or foot traffic, creating visible waves or ripples that make a panel look cheap or defective even though it is structurally sound. Striations interrupt this effect by creating anchor points that resist the movement and by dividing the visual field so the eye cannot track a continuous wave across the panel. A smooth panel 24 inches wide will show oil-canning far more readily than a striated one of the same thickness.
Common striating patterns
Metal roof panels may have striations running lengthwise along the panel (parallel to the ridge line), or in a herringbone or diamond pattern. In standing-seam metal roofing, the ribs themselves function partly as striations. In flat-lock and metal wall panels, manufacturers often add striations as a cosmetic feature as much as a structural one. The pattern is usually part of the coil or blank design, created during the rollforming or stamping process before panels leave the factory.
The depth and spacing of striations are not standardized, so a panel specified as "striated" may differ from one supplier to another. Thinner materials, such as 0.016 inch aluminum or 24-gauge steel, rely more heavily on striations to control perceived flatness. Thicker panels may be striated for appearance alone. The grooves also create slight shadow lines that give a panel visual texture and can hide minor dust or water streaking.
Installers and specifiers should be aware that striations do not eliminate oil-canning in very large single panels or under extreme thermal cycling, and they can trap dirt and water if panel slopes are too shallow or if gutters are poorly maintained. In coastal or dusty environments, striations may require more frequent cleaning than smooth panels.