Understanding Oil Canning on Metal Roofs: Definition and Causes

Oil Canning on Metal Roofs
June 10, 2024

What is Oil Canning?

Oil canning is a visual phenomenon where metal panels, particularly those on roofs and siding, exhibit waviness or distortion. It is an inherent characteristic of light-gauge, cold-rolled flat metal products and is primarily considered an aesthetic issue rather than a structural one. This waviness can appear across various types of metals, including steel, aluminum, zinc, and copper.

Oil Canning on Metal Roofs

Causes of Oil Canning on Metal Roofs

Several factors can contribute to the occurrence of oil canning in metal roofs:

  1. Thermal Expansion and Contraction: Metals expand when heated and contract when cooled. This natural movement can cause stress in the metal panels, leading to visible distortions if the panels are not allowed to move freely​​.
  2. Improper Handling and Installation: Over-tightening fasteners, incorrect alignment, and mishandling during transport and installation can introduce stresses that result in oil canning​​. Panels should be handled with care to avoid unnecessary bending or twisting.
  3. Uneven Substrate or Underlayment: Installing metal panels over uneven surfaces can cause the panels to stress and deform. A flat and even substrate is crucial for minimizing oil canning​​.
  4. Roll Forming and Manufacturing Processes: The stresses induced during the roll forming and slitting processes can also contribute to oil canning. Poorly maintained or calibrated equipment exacerbates this issue​.

Impact of Oil Canning on Metal Roof Performance

While oil canning is primarily a cosmetic issue, its presence can affect the perceived quality of the roof. It does not impact the structural integrity or functionality of the roofing system but can be an aesthetic concern for property owners​​.

Identifying Oil Canning on Metal Roofs

Oil canning is usually identified by its characteristic wavy appearance on the flat surfaces of metal panels. It can be more pronounced under certain lighting conditions and viewing angles. Panels with darker colors and high-gloss finishes tend to show oil canning more prominently than lighter, matte-finish panels​​.

Preventing and Minimizing Oil Canning

To prevent and minimize the occurrence of oil canning, consider the following measures:

  1. Material Selection: Using heavier gauge metals and selecting panels with striations or minor ribs can reduce the likelihood and visibility of oil canning​​.
  2. Proper Installation Techniques: Ensure panels are correctly aligned, avoid over-tightening fasteners, and allow for adequate thermal movement. This helps to reduce stress on the panels​.
  3. Surface Preparation: Install panels on a flat and even substrate, and use appropriate underlayment to provide a stable base for the metal panels​​.
  4. Handling and Storage: Proper handling and storage practices, such as carrying panels perpendicular to the ground and providing adequate support during transport, can prevent the introduction of stresses that cause oil canning​​.
Oil Canning on Metal Roofs

Solutions for Existing Oil Canning Issues

If oil canning is already present, there are several solutions to mitigate its appearance:

  1. Adjusting Fasteners: Loosening or re-aligning fasteners can sometimes relieve stress and reduce oil canning​​.
  2. Panel Replacement: In severe cases, replacing affected panels with ones that have striations or are of a heavier gauge can help​.
  3. Using Backer Rods: Installing a backer rod under the center of each panel during installation can significantly reduce stress wrinkling by pushing any ripples towards the edges where they are less noticeable​​.

Conclusion: Maintaining Aesthetic and Functional Integrity of Metal Roofs

Oil canning is a common issue in metal roofing that, while primarily aesthetic, can be minimized with proper material selection, handling, and installation techniques. Understanding its causes and implementing preventive measures can help maintain the visual appeal of metal roofs.

For more information on metal roofing solutions and professional advice, visit Roof for Life Alberta.

By following best practices and seeking professional installation services, homeowners can enjoy the durability and aesthetic appeal of metal roofs while minimizing the impact of oil canning.