# What Is Oil Canning on a Metal Roof, and Is It a Defect?

> Oil canning explained — what causes the wavy, rippled look on metal panels, whether it is a defect, and what actually reduces it.

URL: https://metalroofingboise.net/guide/oil-canning-metal-roof/

Oil canning is the wavy, rippled appearance that can develop on flat sections of metal panels, caused by minor stresses in the metal from rolling, forming, or thermal movement. It is almost always cosmetic, not structural, and is more visible on lighter colors, lower-gauge panels, and flatter panel profiles like standing seam.

## 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.

## FAQ

**Is oil canning covered under a metal roof warranty?**

Most manufacturers explicitly exclude oil canning from warranty coverage because it is considered an inherent characteristic of flat metal panels rather than a manufacturing defect. Worth confirming with the specific manufacturer, but don't expect it to be a warrantable issue.

**Does oil canning mean my roof was installed incorrectly?**

Not necessarily — it can happen even on a correctly installed roof, since it relates to the metal coil's inherent flatness variation and thermal movement. That said, incorrect clip spacing or an uneven substrate underneath can make it worse, so it's worth asking your installer about their approach.

**Can oil canning get worse over time?**

It can become more visible as the panel goes through repeated thermal cycles, particularly on lighter-colored panels in direct low-angle sun. It generally does not worsen to the point of functional failure — it stays a cosmetic characteristic rather than progressing into a structural issue.