What is Oil Canning?

According to the Metal Construction Association, oil canning can be defined as “visible waviness in the flat areas of metal roofing and metal wall panels.” Basically, the metal panels can “wrinkle” under stress, which is called oil canning.

Oil canning is a very common occurrence, and is not a cause for rejection or a warranty claim.

Oil canning may be more or less visible depending on the time of year, the position of the sun, and the angle from which it is viewed.

What causes oil canning?

A number of factors can contribute to oil canning, including stress caused in the production of the metal coil or the manufacturing. Other causes could include an uneven roof structure and poor installation practices.

Are there ways to reduce oil canning?

While there is no guaranteed method to eliminate it 100%, there are steps you can take minimize the appearance of oil canning.

• Metal Thickness: Purchase a thicker metal, which will bend and warp less than thinner metal.
• Patterns: Purchasing metal with V-ribs or striations can make oil canning less obvious, although it will not eliminate it entirely.
• Textured: Oil canning is less noticeable with textured panels since textured panels reflect less light. High gloss metal reflects more light, which increases the visibility of waviness and warping.
• Panel Width: Choosing a narrow width panel can reduce the appearance of oil canning. The wider the panel, the more flat space there is for oil canning to appear.
• Handling: Always carry the panels perpendicular to the ground, supporting them every 10 to 12 feet. Avoid twisting the panels.
• Measuring: Precise measurement and installation helps avoid misalignment of the panels, which causes stresses that could result in oil canning.
• Inspect the Roof Deck: Before installation, check the roof deck for any bowing or uneven planes. An uneven roof deck is one of the most common causes of oil canning.
• Fastening: Avoid over-driving the fasteners and avoid angling the fasteners. Both can cause stress to the panels which will show up as oil canning.
• Backer Rod: Some designers recommend adding compressible foam strips called backer rods behind the panel to relieve panel stress.
• Ridge Cap: Installing a Snap-Z ridge cap can help reduce or eliminate oil canning in the ridge cap. See this article for more information.

Conclusion

If you notice some mild oil canning on your roof, don’t panic! In many cases, some of the stress on the panels will work out over time, reducing the appearance of oil canning. It may take several seasons until your roof completely adapts to its final form.

For a more in-depth explanation of oil canning, we recommend this article by the Metal Construction Association.