In the world of metal roofing, the term “oil canning” evokes a mix of
concern and curiosity. This phenomenon, characterized by visible
waviness or distortion in the flat areas of metal panels, often sparks
debate among architects, builders, and homeowners alike. While
primarily an aesthetic issue, oil canning can influence perceptions of
quality and craftsmanship, making it a topic worth exploring.
The Origins of Oil Canning
To understand oil canning, one must delve into the journey of a metal
panel, from raw material to finished product. Metal roofing panels are
typically made from thin sheets of steel, rolled and formed into specific
profiles. During this manufacturing process, internal stresses can
develop within the metal. These stresses, if not adequately managed,
become the seeds of future oil canning.
The phenomenon is named after the old oil cans, which, when pressed,
would exhibit a similar waviness. Like those cans, metal roofing panels
are susceptible to slight deformations when subjected to external
pressures or internal stresses.
Factors Contributing to Oil Canning
Several factors contribute to oil canning, each playing a role in the final
appearance of a metal roof:
Material Stress: The process of rolling and forming metal panels can
introduce internal stresses. If these stresses are not uniformly
distributed, they can cause the metal to warp slightly, leading to oil
canning.
Thermal Expansion and Contraction: Metal expands when heated
and contracts when cooled. These temperature-induced changes can
cause the panels to buckle slightly if not allowed to move freely.
Installation Practices: The way panels are installed can significantly
impact their appearance. Over-fastening, uneven substrates, or improper
handling during installation can all lead to oil canning.
Handling and Storage: Damage during transport, handling, or
storage can leave dents or bends in the metal, predisposing it to oil
canning when installed.
Mitigating Oil Canning
While oil canning cannot be entirely eliminated, several strategies can
help mitigate its appearance:
Proper Panel Design: Designing panels with stiffening ribs or using
thicker materials can reduce the likelihood of oil canning. These features
add rigidity to the panels, helping them maintain their shape.
Proper Panel Specifications*: Utilizing a textured finish paint will
mitigate the appearance of oil canning. Increasing the gauge rto 26 Ga.
for residential and 24 Ga. for commercial metal roofing systems can be
an effective approach. * We do not recommend a smooth finish with
dark colors.*
Correct Installation Techniques: Following manufacturer guidelines
for installation, including the proper use of fasteners and allowances for
thermal movement, can minimize oil canning. Ensuring the substrate is
even and stable is also crucial.
Quality Control in Manufacturing: Using high-quality materials and
maintaining strict quality control during manufacturing can help minimize
internal stresses. Stress-relieving techniques, such as annealing, can
also be employed.
Education and Communication: Educating clients about oil canning
is essential. By setting realistic expectations and explaining that oil
canning is a naturally occurring phenomenon, builders and
manufacturers can help clients appreciate the functional integrity of their
roofing, despite minor aesthetic imperfections.
A Case Study: The Modern Office Building
Consider a modern office building with a sleek metal roof. The architects
selected standing seam metal panels for their clean lines and
contemporary look. However, as the seasons changed, subtle waves
appeared on the surface of the panels. Concerned about potential
structural issues, the building owners consulted a roofing expert.
Upon inspection, the expert explained that the waviness was due to oil
canning, primarily a result of thermal expansion and contraction. The
metal panels, though slightly wavy, remained structurally sound. To
address aesthetic concerns, the expert recommended installing
additional stiffening ribs on future panels and ensuring proper installation
practices were followed.
Conclusion
Oil canning in metal roofing is a reminder of the material’s dynamic
nature. While it can pose aesthetic challenges, understanding its causes
and implementing strategies to mitigate its effects can help maintain both
the visual appeal and structural integrity of metal roofs. As the industry
continues to innovate, the quest for a perfectly smooth metal roof may
remain elusive, but the pursuit itself drives advancements in materials
and methods, benefiting all involved.
At the end of the day it’s all about risk vs. reward. Standing seam metal
roofs offer a life expectancy of 50-60 years, are virtually maintenance
free, are made from upwards of 90% recycled steel, are 100%
recyclable, and can help reduce utility load by 20%. With rewards that
high, metal roofing can’t be ignored.
