What Is Oil Canning on a Metal Roof?

What oil canning actually is

Oil canning is the wavy, rippled visual distortion that can appear on the flat sections of metal roofing and siding panels — most noticeable on standing seam’s large flat pans, less visible on exposed-fastener’s ribbed or corrugated profiles because the ribs physically interrupt the flat surface. It’s caused by minor internal stresses in the metal coil from the rolling and forming process, combined with the panel’s thermal expansion and contraction over its life.

Is it a defect?

No — it’s an inherent characteristic of flat metal panels, not a manufacturing flaw or an installation failure by default. Every major metal panel manufacturer explicitly excludes oil canning from warranty coverage for this reason. That doesn’t mean nothing can be done about it — it means it’s a known tradeoff of the material and profile, not a problem to fix under warranty.

What makes it more or less visible

• Panel gauge — heavier gauge (thicker) panels resist oil canning noticeably better than lighter gauge. This is one of the real reasons to spec heavier gauge on a visible roofline.
• Color and finish — darker colors and matte finishes hide oil canning better than light, glossy finishes, which reflect light in a way that emphasizes surface irregularities.
• Panel width — narrower panels show less oil canning than wide flat pans, simply because there’s less flat surface area to distort.
• Striations — some standing seam profiles roll shallow ribs or striations into the panel face specifically to break up the flat surface and reduce visible waviness.
• Substrate flatness — an uneven deck underneath can telegraph through the panel and make oil canning worse; a flat, well-prepared substrate helps minimize it.
• Clip spacing — correct clip spacing, matched to the manufacturer’s engineering spec, reduces the stress concentration that contributes to oil canning.

Should it change which panel you choose?

Not necessarily. Oil canning is a real, valid consideration on a highly visible roofline in direct sun, but it’s a cosmetic tradeoff, not a reason to avoid standing seam or metal roofing generally. If it’s a specific concern for your project, we’ll walk through gauge, color, and profile options at the inspection that meaningfully reduce it — including whether exposed- fastener’s ribbed profile might be a better fit if the flat-panel look isn’t essential to you.

Bottom line

Oil canning is a cosmetic characteristic of flat metal panels, not a defect or a sign your roof is failing. It’s real, it’s visible in the right light, and it can be minimized with gauge, color, and installation choices — but it’s not a reason to rule out metal roofing. Call (208) 279-6903 if you want to talk through panel options that reduce it for your specific roof.