Oil Canning in Standing Seam Metal Roofs.
- The Guardian
- Dec 1, 2025
- 3 min read
Oil canning is a common issue that can affect standing seam metal roofs, often causing concern for homeowners, builders, and architects. This phenomenon appears as visible waviness or distortion in the flat areas of metal panels, which can detract from the roof’s appearance and raise questions about its durability. Understanding what causes oil canning, how to identify it, and the best ways to prevent it can help maintain the aesthetic and functional quality of metal roofs.
What Is Oil Canning in Standing Seam Metal Roofs?
Oil canning refers to the visible waviness or buckling that appears on the flat surfaces of metal roofing panels. It looks like ripples or waves and is most noticeable on large, flat metal areas exposed to sunlight. This effect is purely cosmetic and does not usually indicate structural failure or leaks, but it can be unsightly and cause concern for property owners.
Standing seam metal roofs consist of long, vertical panels joined by raised seams. The flat areas between these seams are prone to oil canning because of the metal’s natural tendency to expand, contract, and flex with temperature changes and installation stresses.
Causes of Oil Canning
Several factors contribute to oil canning in standing seam metal roofs. Understanding these causes helps in both preventing and addressing the issue.
Metal Properties and Thickness
Metal panels have inherent stresses from the manufacturing process. Thinner metals are more flexible and prone to visible waviness. Thicker metals resist oil canning better but add weight and cost.
Panel Width and Length
Wider and longer panels tend to show oil canning more clearly because there is more flat surface area to flex. Narrower panels reduce the visible effect.
Installation Techniques
Improper installation can increase the risk of oil canning. Over-tightening fasteners, uneven fastening, or not allowing for metal expansion can cause stress that leads to waviness.
Temperature Changes and Expansion
Metal expands and contracts with temperature fluctuations. A 30' long steel panel can expand or contract about 1/2" over a 100F degree temperature change. Aluminum panels will expand and contract at about twice that rate.
Substrate and Support
Uneven or flexible roof decks can cause metal panels to flex and show oil canning. A solid, flat substrate reduces the risk.
How to Identify Oil Canning
Oil canning is easy to spot once you know what to look for:
Visible waves or ripples on the flat areas of metal panels.
Changes in appearance depending on the angle of sunlight or viewing position.
Usually more noticeable on light-colored or reflective metal panels.
Does not affect the raised seams or edges as much as the flat areas.
It’s important to differentiate oil canning from other issues like panel buckling, dents, or corrosion, which may require different solutions.
Why Oil Canning Happens More in Standing Seam Roofs
Standing seam roofs have large flat panels between raised seams, which makes oil canning more visible compared to other metal roof types with more textured or ribbed surfaces. The long, continuous panels are also more susceptible to thermal expansion and contraction, increasing the chance of waviness.
Solutions to Oil Canning
While oil canning is mostly a cosmetic issue, many property owners want to minimize or eliminate it for aesthetic reasons. Here are practical solutions:
Design and Material Choices
Use thicker gauge metal panels where possible to reduce flexibility.
Choose narrower panel widths to limit the flat surface area.
Select metals with higher yield strength to resist deformation.
Consider finishes and coatings that reduce reflectivity, making oil canning less visible.
Including striations in the panel reduces the flat surface areas, reducing the visibility and appearance of oil canning.
Proper Installation Practices
Allow for thermal expansion by not over-tightening fasteners.
Use correct fastening patterns recommended by manufacturers.
Ensure the roof deck is flat and stable before installation. Tear-off and removal of existing roofing materials, along with deck prep is just as important as the installation of the new metal system.
Avoid unnecessary handling or bending of panels during installation.
Post-Installation Fixes
Panel stretching or flattening by professionals can reduce visible waviness.
Installing additional clips or supports can help stabilize panels.
In extreme cases, panel replacement may be necessary.
Preventive Maintenance
Address any substrate issues or fastener problems during the tear-off and deck prep stage.
Keep the roof clean to avoid dirt buildup that can highlight surface irregularities.
When Oil Canning Is Not a Problem
It’s important to understand that oil canning DOES NOT affect the roof’s waterproofing or structural integrity. Many metal roofs with oil canning perform well for decades without leaks or damage. If the waviness is not aesthetically bothersome, it should be left as is. In some cases, such as in a historical area of town, oil canning may be a requirement for permitting in order to maintain the "historic look" of the property. Be sure to speak with your sales rep if you find yourself in this particular situation.
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