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Understanding Striations and Preventing Oil Canning in Metal Roofing

Metal roofing with striations
Striations can help prevent the visual appearance of oil canning. Photo courtesy of K&L Roofing, Inc.

Metal roofing has become a popular choice for both residential and commercial buildings due to its durability, energy efficiency, and modern aesthetic. However, one common issue that can arise with metal roofing is the appearance of oil canning. Understanding oil canning and knowing how to prevent it using striations (and other best practices) is crucial for ensuring a high-quality, visually appealing roof.


Metal roof with striations
Striations add stiffness to the metal panels.

What Are Striations?

Striations refer to deliberate, shallow grooves or lines rolled into the surface of metal roofing panels. These lines can be either subtle or more pronounced, depending on the design. The primary purpose of striations is to enhance the structural integrity of the metal panels and improve their aesthetic appeal.



Striations help to:

1. Minimize Glare: By breaking up the surface of the metal, striations reduce the amount of light that reflects off the roof, thereby reducing glare.

2. Prevent Oil Canning: Striations add stiffness to the metal panels, helping to reduce the visible waviness known as oil canning.


Metal roof with oil canning
Metal roof with oil canning from improper installation. Photo courtesy of Metal Roofing Alliance.

What Is Oil Canning?

Oil canning is a term used to describe the visible waviness or distortion that can appear on flat metal surfaces, such as roofing panels. This effect is often most noticeable in the broad, flat areas of the panels and can be caused by several factors, including:

1. Material Stress: Residual stresses from the metal manufacturing process can lead to oil canning.

2. Thermal Expansion: Temperature fluctuations can cause the metal to expand and contract, leading to waviness.

3. Improper Installation: Incorrect fastening techniques or inadequate support can exacerbate oil canning.

4. Panel Width: Wider panels are more prone to oil canning than narrower ones.


Preventing Oil Canning

While it is impossible to eliminate the risk of oil canning entirely, several strategies can significantly reduce its likelihood and severity:

True Metal Supply's DuraLock 100 metal roof panel with striations
True Metal Supply's DuraLock 100 metal roof panel with striations

1. Design Considerations:

  • Striations: Incorporating striations into the design of metal roofing panels adds rigidity and reduces the flat surface area, helping to minimize oil canning. (See DuraLock 100 standing seam metal roof panel with striations.)

  • Embossing or Stamping: Adding embossed or stamped patterns can also help to break up flat areas and reduce visible distortions. (See stamped Victorian Shingles below.)

Stamped Victorian Metal Shingles
Stamped Victorian Metal Shingles
  • Ribbing: Including ribs or stiffening ribs along the panel can further enhance structural integrity. (See Tuff-Rib metal panel image below.)

Ribbing Example: True Metal Supply's Tuff-Rib metal roofing.
Ribbing Example: True Metal Supply's Tuff-Rib metal roofing. Photo courtesy of Friend In Roofing

2. Material Selection:

  • Thicker Gauge Metal: Thicker metal is less prone to oil canning due to its increased rigidity.

  • High-Quality Alloys: Using higher quality metal alloys can improve performance and reduce the risk of oil canning.


3. Installation Techniques:

  • Proper Fastening: Ensuring that fasteners are correctly spaced and adequately tightened can help to prevent stress points that lead to oil canning.

  • Adequate Support: Providing proper support for the roofing panels during installation can reduce the chance of distortion.

  • Allowing for Thermal Expansion: Designing the roof to accommodate thermal movement, such as using floating clips, can mitigate the effects of temperature changes.


4. Manufacturing Practices:

  • Stress Relieving: Ensuring that the metal undergoes proper stress-relieving processes during manufacturing can help to reduce residual stresses that contribute to oil canning.

5. Using Backer Rods:

  • Additional Support: Backer rods can also be used in metal roofing to provide additional support and minimize the appearance of oil canning. Placing backer rods behind the metal panels can help distribute stress more evenly and reduce the likelihood of waviness.

  • Installation: When installing backer rods, ensure they are positioned correctly and securely behind the panels to offer consistent support across the entire surface area.


Conclusion

Striations play a crucial role in both enhancing the appearance and structural integrity of metal roofing panels. By understanding the causes of oil canning and implementing design, material, and installation strategies to prevent it, you can ensure a durable and aesthetically pleasing metal roof. While some degree of waviness may be inherent to the nature of metal roofing, careful planning and attention to detail can significantly mitigate its impact, resulting in a more visually appealing and long-lasting roof.

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