If you have ever looked up at a metal roof and noticed what appears to be subtle waves or ripples across an otherwise flat panel surface, that is oil canning. It is a common occurrence in the metal roofing industry and what causes oil canning and how to address it will help you make more informed decisions throughout the entire roofing process.
What Is Oil Canning?
Oil canning on a metal roof is defined as a perceived waviness in light-gauge, cold-rolled flat metal products. It is an inherent characteristic of metal panels and can appear across any type of metal used in roofing construction, including steel, aluminum, copper, and zinc. The waviness tends to be most visible in the broad, flat areas between panel seams, and its appearance can vary significantly depending on the angle of view, the time of day, the season, and the amount of direct sunlight hitting the surface.
One important distinction to understand is that oil canning is a cosmetic issue, not a structural one. It does not compromise the waterproofing, durability, or long-term performance of a metal roof system. For this reason, most paint, substrate, and weathertight warranties do not cover oil canning as a claimable defect. While the waviness may be visually noticeable, a panel exhibiting oil canning is still performing exactly as intended.
Causes of Oil Canning on Metal Roofing
Oil canning does not have a single root cause, which is part of what makes it so difficult to completely eliminate. It can originate during manufacturing, storage, transportation, or installation, and in many cases, several contributing factors are present simultaneously.
During the production process, three specific stress conditions can be introduced into the metal: a full center condition, where the middle of the sheet is longer than the edges and creates buckling down the center; a wavy edge condition, where the edges of the sheet or coil are longer than the middle; and camber, where the sheet or coil curves slightly when laid flat rather than lying in a straight line. Any of these production stage stresses can set the stage for visible oil canning once panels are installed.
Beyond manufacturing, metal has a memory. When a coil is roll-formed or slit into panels, the metal is always trying to return to its original pre-formed state. This internal tension can cause warping and waviness as the material moves subtly over time.
Improper fastener installation is another frequent contributor. Over-driven fasteners place concentrated stress on the male leg of a standing seam panel, and fasteners driven in at an angle introduce uneven pressure that distorts the flat panel surface. Both scenarios can trigger oil canning that would not have otherwise appeared.
Thermal movement is also a significant factor. Metal naturally expands in heat and contracts in cooler temperatures. When panels are double pinned at their edges, this movement is restricted, causing stress to build up and manifest as waviness across the panel face. Allowing panels adequate room for thermal expansion during installation is essential.
An uneven substrate is one of the most common on-site causes. Whether the roof deck is made of plywood, OSB, or metal, any bowing, concave areas, or out-of-plane sections will be reflected through the installed panels. Metal conforms to what it is laid upon, meaning an irregular surface below will translate into visible irregularities above. Similarly, underlayment that is not laid flat creates an unstable base that produces the same result.
Panel misalignment during installation can also cause oil canning. If panels are not correctly aligned from ridge to eave and stress is applied to force them into position without reinstalling, the resulting tension in the metal will often appear as waviness. Panels that are handled improperly during transport and installation are also at risk. Metal panels should always be carried perpendicular to the ground and supported every 10 to 12 feet. Allowing panels to sag in the middle during handling can introduce permanent distortion.
Finally, settling of a building structure after installation can put tension on already-secured panels, causing stress wrinkling in metal siding and roofing that was initially installed flat.
What to Look for Before and During Installation
Preventing oil canning is far easier than addressing it after panels are fully installed. There is a straightforward inspection process that contractors, installers, and building owners can use to catch the problem early.
Start by inspecting the storage conditions before installation begins. Materials should be stored dry, fully supported, and positioned so that no twisting or uneven pressure is placed on the packaged panels. From there, remove a panel or two from the bundle and hang them horizontally, supporting them along the top rib every 10 to 12 feet. Observe them for any signs of waviness in their natural, unrestrained state.
Watch how panels are handled as they move from the bundle to the installation area. Movement in both horizontal and vertical orientations can reveal stress or warping that is already present. Before fastening anything, lay the panels flat on the roof deck without any attachments and observe them carefully. This step also serves as an opportunity to check the deck itself for bowing, concave areas, or uneven planes.
Once installation begins, install one panel adjacent to an already-secured panel and observe for flatness before continuing. Then install clips and fasteners according to the manufacturer’s specifications and check for any newly apparent waviness. If what appears to be excessive oil canning is noticed at any point during this process, stop installation and have the project owner assess the situation before proceeding.
7 Ways to Minimize Oil Canning on Metal Roofing
No approach guarantees complete elimination of oil canning because it is an inherent property of metal. However, the following measures significantly reduce the likelihood and visibility of the issue.
Choose a thicker metal gauge. Heavier gauge metal is physically harder to distort, which makes it more resistant to the stresses that cause oil canning. A 22-gauge panel, for example, is thicker and more resistant to waviness than a 26-gauge panel.
Use stiffening ribs or striations. Rib rollers, also called stiffening ribs, are manufactured indentations rolled into the flat portion of a panel between the seams. Common rib types include V-ribs, bead ribs, and pencil ribs. Striations are linear grooves that run parallel to the seams and span the full width of the panel. Both options reduce the amount of flat, uninterrupted surface area, which makes any waviness far less visible. Striations are considered more effective than stiffening ribs because they eliminate flat surface area across the entire panel. Neither option increases the cost of the panels.
Select a narrower panel width. Oil canning is most visible on wide, flat surfaces. Choosing panels that are 18 inches or narrower reduces the area over which waviness can develop and makes any waviness that does occur less apparent.
Opt for a low-gloss or matte finish. High-gloss finishes reflect more light, which amplifies the visual shadow effect that makes waviness noticeable. Low-gloss and matte finishes reduce reflectivity and make oil canning much harder to detect. Lighter paint colors also show oil canning less than darker tones.
Ensure the roof deck is level and in-plane. Before any panels are installed, verify that the substrate is consistent, flat, and free of bowing in either direction. Installing panels on an uneven deck is one of the leading on-site causes of oil canning, and correcting the deck before installation is always easier than addressing the result after the fact.
Purchase tension-leveled metal. Tension-leveled coil has been stretched past its yield point, meaning it can no longer return to its pre-rolled shape. This process removes the internal memory that causes metal to warp, making tension-leveled material significantly more resistant to oil canning than standard coil.
Use backer rod or shimming material under clips. For installations over solid substrates, compressible foam backer rod or other shimming materials placed beneath the clips can help redistribute pressure and reduce stress on the panel face. This technique works by causing the center of the panel to pillow slightly and uniformly, which relieves the localized stress responsible for visible waviness.
Should I Still Use Metal Roofing If There Is Oil Canning Present?
The short answer is yes. Oil canning has no effect on the longevity, weather resistance, or structural performance of a metal roof. A roof exhibiting mild oil canning will still shed water, resist wind, and outlast most other roofing materials. Metal roofing systems are commonly rated for a lifespan of 40 to 60 years, and oil canning does not reduce that performance in any meaningful way.
That said, it is worth setting realistic expectations before committing to a metal roof. Because oil canning is inherent to light-gauge metal products, no manufacturer or installer can guarantee a completely wave-free result. Any contractor who makes that promise should be viewed with skepticism. What a qualified contractor can do is follow best practices during substrate preparation, panel handling, and installation to minimize the likelihood and visibility of oil canning as much as possible.
If oil canning appears after installation, some improvement may occur on its own. Metal often works out minor stresses over multiple heating and cooling cycles as the roof goes through seasonal temperature changes. In cases where oil canning is more pronounced or concerns you aesthetically, consult with a professional roofing contractor who specializes in metal systems. They can evaluate whether the cause is installation-related and whether any corrective measures are appropriate. For most homeowners and building owners, mild oil canning becomes nearly invisible once you step back from the roof and stop looking for it. When viewed from the ground at normal angles, especially on a matte-finished or lightly colored panel, it is rarely noticeable.
FAQs: Oil Canning
Our most frequently asked questions from homeowners about their experiences with oil canning and whether a metal roof was right for them:
Is oil canning normal on a metal roof?
Yes. Oil canning is considered an industry-acknowledged, inherent characteristic of light-gauge cold-formed metal products. It is not classified as a defect, and it is not covered under standard metal roofing warranties.
How common is oil canning?
Oil canning is common across all metal roofing and wall panel systems. Because it can develop conditions at any stage from manufacturing through installation, virtually any metal roof has some degree of potential for it. The visibility varies widely depending on panel type, color, finish, and lighting conditions.
Are there different types of metal roofing that are less prone to oil canning?
Yes. Corrugated panels are the least prone to visible oil canning because they have little to no flat surface area between ribs. Standing seam panels with narrow widths, stiffening ribs, or striations perform better than wide, flat standing seam panels. Exposed fastener panels with heavy ribbing, such as PBR panels and R-panels, also show significantly less oil canning than smooth standing seam profiles. Regardless of panel type, thicker gauge metal and matte or low-gloss finishes will always reduce the visibility of oil canning compared to thinner, high-gloss alternatives.
DaBella Is the Go-To Roof Replacement Contractor Ready to Take on Your Next Project
DaBella is a trusted roof replacement contractor with the experience and certifications to handle both metal and asphalt roofing systems at a prominent level. As a GAF Master Elite contractor—a designation earned by fewer than 2% of roofers nationwide—DaBella offers access to premium products like GAF TimberSteel and GAF Timberline HDZ. Homeowners can choose from a wide range of colors and styles designed to complement virtually any home, all installed to strict manufacturer standards for long-term performance.
Projects completed by DaBella can also qualify for the GAF Golden Pledge Warranty, one of the most comprehensive warranties available in the residential roofing industry. This level of coverage reflects both the quality of the materials and the precision of the installation. If you are planning a roof replacement and want a solution built for durability, performance, and long-term value, DaBella is ready to help guide you through the process from start to finish. Contact us today at 844-DaBella.
