Metal roofing is known for its durability, clean lines, and architectural appeal—but for many homeowners and builders, one visual imperfection causes concern: oil canning. This subtle waviness or rippling in flat metal panels doesn’t affect structural performance, but it can impact aesthetics and create confusion for property owners.
In this comprehensive guide, we’ll explain what oil canning is, what causes it, why it’s misunderstood, and most importantly—how to prevent or minimize it when selecting and installing a metal roofing system.
1. What Is Oil Canning?
Oil canning is the visible distortion in the flat areas of metal panels that creates a wrinkled, wavy, or dimpled appearance. It’s most noticeable in light reflections and tends to appear in flat-profile metal roofing or siding, especially on standing seam panels.
Think of it like the subtle warping you might see in a soda can or sheet metal when pressed unevenly. It’s not a defect—it's an inherent characteristic of thin-gauge metal under stress.
2. Is Oil Canning a Functional Problem?
No. Oil canning is purely cosmetic. It does not affect waterproofing, structural integrity, or product performance.
-
Panels with oil canning will still shed water and snow effectively.
-
Fastener integrity and wind resistance remain unchanged.
-
Manufacturer warranties often do not cover oil canning, as it is not a manufacturing flaw.
However, it can be a visual distraction for homeowners who expect perfectly flat surfaces, especially on high-end, modern builds.
3. What Causes Oil Canning?
Oil canning is caused by stress in the metal panel that becomes visible due to reflection or surface tension. Several contributing factors include:
A. Thermal Expansion and Contraction
-
Metal expands with heat and contracts as it cools.
-
Improper allowance for this movement causes buckling or rippling.
B. Panel Design and Profile
-
Wide, flat panels are most susceptible.
-
The thinner and wider the panel, the more likely oil canning will be visible.
C. Installation Practices
-
Over-tightened fasteners or misaligned clips can restrict natural movement.
-
Uneven substrate or improper deck preparation can transfer stress to the panel.
D. Coil Stress or Fabrication Flaws
-
Residual stress in the metal coil during manufacturing or roll forming can cause the metal to “relax” unevenly.
-
Poorly formed panels can buckle even under perfect installation conditions.
4. Where Is Oil Canning Most Noticeable?
-
Standing seam roofs with wide flat areas between seams (typically 16" to 24")
-
Wall panels in vertical siding applications
-
Light-colored or high-gloss finishes (which reflect more light)
-
Low-slope roofs where panels are more visible from the ground
Panels viewed at a shallow angle, especially during sunrise or sunset, may appear more wavy even if oil canning is minimal.
5. How to Minimize or Prevent Oil Canning
While you can’t always eliminate the possibility, you can significantly reduce its appearance through design and installation best practices:
A. Choose a Panel with Minor Ribbing or Striations
-
Ribbed, pencil bead, or striated panels break up flat surfaces and reduce the visual impact of waviness.
-
Some panel systems offer a textured or embossed finish for this reason.
B. Use Heavier Gauge Metal
-
24-gauge or thicker material is more rigid and less prone to flexing.
-
Avoid 29-gauge metal in high-visibility areas if appearance is a priority.
C. Select Low-Gloss or Textured Finishes
-
Matte or low-sheen coatings reduce the amount of light reflection, hiding surface irregularities.
-
Textured or “crinkle” finishes are especially good at masking oil canning.
D. Proper Substrate and Decking Preparation
-
Ensure the roof deck is smooth, flat, and fully supported.
-
Substrate irregularities translate directly into visible distortions.
E. Allow for Thermal Movement
-
Use slotted clips or floating systems that allow panels to expand and contract freely.
-
Avoid pinning panels with fasteners that restrict movement.
F. Work with Experienced Fabricators
-
Panels formed with proper tension leveling and maintained equipment are less prone to residual stress.
-
Ask about flatness standards and coil quality when ordering panels.
6. Why It’s Often Misunderstood
Many homeowners or builders who are unfamiliar with metal roofing may see oil canning and mistakenly assume:
-
The panel is defective
-
The installation was poor
-
The roof will fail or leak
In reality, oil canning is not a flaw—it's an aesthetic consideration, and in some architectural styles (such as industrial or rustic designs), it’s even accepted or embraced as part of the natural look of metal.
7. What Do Manufacturers Say About It?
Most major metal roofing manufacturers include disclaimers stating:
“Oil canning is an inherent characteristic of light-gauge cold-rolled flat metal and is not cause for rejection.”
Some offer guidance on how to minimize it but will not cover it under warranty.
8. What to Do If You Notice Oil Canning on Your Roof
If your roof is newly installed:
-
Contact your installer to review the installation against best practices.
-
Verify if striated panels or thicker gauge could have been used.
If you’re planning a project:
-
Ask your contractor or supplier about oil canning mitigation options upfront.
-
Request samples or photos of installed panels before choosing a profile.
Conclusion: Set Expectations, Choose Smartly, and Build Confidently
Oil canning is a natural characteristic of metal roofing—not a performance issue or defect. With proper planning, panel selection, and installation practices, it can be minimized or rendered nearly invisible.
As architectural design trends continue to favor clean lines, wide panels, and flat finishes, it’s essential for homeowners, designers, and contractors to understand oil canning and make informed choices to balance appearance with performance.
By embracing the right combination of materials and technique, you’ll enjoy a beautiful, durable metal roof that delivers both style and strength—for decades to come.
