What causes oil canning and how should it be addressed with product specifications

Oil canning is something you see when a metal panel appears wavy or distorted. Oil canning is an inherent characteristic of cold-rolled flat metal panels and isn’t cause for rejection but it can be an aesthetic concern in some cases.

While oil canning can happen with all metal products regardless of the material substrate (think metals like aluminum, copper, zinc, and steel), It is most commonly an issue with standing seam roof and architectural wall systems.

What causes oil canning?

Determining the root cause of oil canning is difficult to definitively identify but possible causes include:

• Inconsistencies in the roof substructure
• Panels being twisted during installation
• Over-driving fasteners
• Movement of the underlying structure
• Uneven stresses at the fastening points
• Temperature variation along the roof if one part is in direct sunlight and another in the shade)
• Installing wider panel widths
• Issues with the rolling process at the mill including poorly adjusted or worn roll formers
• Distortions introduced during the slit or forming process

How to Address Oil Canning within Product Specifications

Since there are several possible causes for oil canning, the next logical question is what can be done to avoid the issue. As a designer and specifier you have control over some of them.

First and foremost, have a frank conversation with your building owner during the design phase. Metal panels offer a great number of benefits ranging from life expectancy to performance but their Achilles heel “can be” the topic of oil canning. But that doesn’t have to be the case. Explain the phenomena to your owner and learn their appetite for oil canning on their project. Many owners understand and have minimal concerns; others however have a near zero tolerance. While nothing can guarantee the absence of oil canning, consider addressing the following in your specification and/or product selection for those situations where oil canning is a major concern.

1. Ensure suitability of substructure/roof deck. As mentioned in our eBook “18 Ways to Reduce Risk When Specifying a Standing Seam Metal Roof Panels,” it is critically important to set the expectation in your specification that the installer accepts the substrate before commencing installation. This means the deck is within the required plane and free from defects. Any deviation in the deck, issues with squareness or camber of the underlayment can cause stress on the panel and inadvertently bind the clips or panels which can result in oil canning.
2. Specify Striations for Pan Conditions. One of the easiest (and cheapest!) ways to address oil canning is by specifying a pan condition called striations. Striations involve putting a very minor bend in the flat of the panel every few inches. These striations can help absorb thermal cycling and reduce the appearance of oil canning. Once the panel is installed, these minor bends are rarely noticeable. Pan conditions such as pencil ribs or planks are also available but are usually more noticeable after installation. Most reputable manufacturers do not charge extra for these pan conditions so they have quickly become a common approach to address oil canning concerns..
3. Minimize panel widths. Wider panel widths are more prone to oil canning. So if a panel is offered in 16”, 18” and 24” panel widths, 16” width typically will exhibit the least oil canning. While that seems simple enough, it’s important to remember the economics involved. Material and labor costs will both be higher for narrower panels. Compare for a moment the difference between a 16” panel and an 18” panel on a 100’ single sloped building. 75 panels 16” wide would be required but only 67 panels at 18”. That means 10% more panels are being produced, packaged and shipped by the manufacturer, not to mention handled and installed by the contractor. Narrower panels can be an effective approach to minimize oil canning but they do so with an added cost.
4. Increase the panel gauge. Commercial standing seam panels are most commonly produced in 24 Ga. steel; however, increasing the gauge to 22 gauge for example can also be an effective approach to reduce oil canning. While this approach doesn’t involve any additional production or transportation costs from the manufacturer, the raw material will cost approximately 20% more than 24 ga. steel products. Further some installers will increase their labor due to the fact that the heavier panels require more crew personnel to adequately handle and install. And it’s important to note that if the structure is out of plane, even heavier gauge panels won’t adequately prevent oil canning.
5. Require Contractor Experience. It’s often said that the best defense is a good offense. The same holds true with efforts to reduce oil canning. Reputable contractors understand the importance of a deck that is in plane and free of defects. And they especially understand the nuances regarding the installation of metal panels. Experienced installers know what they should do to avoid oil canning and how to address it if it occurs. There is simply no substitute for contractor experience and setting the expectation in your specification is the place to start.

Want to learn more? Check out this article about oil canning in Metal Construction News.

If you’d like some help with this part of your specification (or any other) Contact Us, we’d love to help.