Oil canning in metal roofing: What roofers need to know

By Justin Ache, Gibraltar Building Accessories.

Oil canning, while a natural cosmetic trait of metal roofing, can easily be addressed with proper care.

If you have ever finished a standing seam roof only to notice a wavy, rippled look in the flat sections, you have seen oil canning. It is one of the most common call-backs in metal roofing and while it is not a performance failure, it can turn into a big headache when owners expect a perfectly flat look. 

What is oil canning? 

Oil canning is the visible waviness in flat areas of metal panels. It happens in roofing and siding, especially with light-gauge steel and wide-flat “architectural” panels. It is not a defect. It is a characteristic of the material. Depending on the time of day and sunlight angle, the waviness can look more or less noticeable. 

Why it happens 

• Thermal movement – Panels expand and contract with temperature swings. If restrained, they can bow or distort in flat areas. 
• Fastener restraint – Over-driving screws or uneven clip spacing can set up stress lines that show as waves. 
• Handling damage – Carrying or twisting panels incorrectly can build in stress before they are even on the roof. 
• Finish and profile choice – Glossy finishes and wide flats magnify the look. 

Oil canning usually comes from a mix of these factors rather than just one mistake. A roof might look flat on install day, but once the sun beats down and the panels start to move, any stress points or wide, glossy surfaces will make the waviness stand out. That is why roofers often notice it showing up later or looking different depending on the time of day. 

Ways to minimize oil canning 

• Choose striated, ribbed or narrower-flat panels over wide-flats. 
• Step up to thicker gauge material when possible. 
• Avoid high-gloss finishes that reflect every ripple. 
• Follow manufacturer handling and installation practices to the letter. 
• Watch your fastener torque. Over-driving is a big culprit. 

Talking to owners 

The biggest frustration with oil canning usually comes from unmet expectations. Educating building owners and GCs before installation is critical: 

• Stress that oil canning is cosmetic, not structural. 
• Show samples with striations or ribs to demonstrate alternatives. 
• Put manufacturer guidance into the spec and submittals. 

Takeaway for roofers

Oil canning is part of the game with architectural metal roofing, but you can limit call-backs by controlling what you can. Panel selection, finish choice, handling and installation technique all matter. Most importantly, set the expectation up front so you are not the one answering the “why does my roof look wavy” call after the job is done. 

For a deeper dive, check out the Metal Construction Association’s educational material on oil canning: metalconstruction.org