Metal Roofing: Understanding Oil Canning, Causes Behind It And Preventive Techniques
With an average life expectancy between 40 to 70 years and an ability to reduce cooling costs by 10 to 25%, it is no wonder why metal roofing is becoming more and more popular. Understanding how to maintain and repair issues that concern metal roofing is crucial for homeowners who are making a decision regarding whether they would like to upgrade to metal shingles or not. Metal roofing is prone to a unique problem known as oil canning. This article will explain exactly what oil canning is, what causes it, and how to prevent it.
What Is Oil Canning?
Let's get down to business. Oil canning is best described as an observed waviness or buckling across flat sheets of metal that is most obvious under specific lighting conditions. Technically speaking, oil canning is basically elastic buckling, or stress wrinkling, and can occur in any type of metal shingles regardless of whether it is made from copper, zinc or even aluminum. Generally speaking, the amplitude of the waviness in metal shingles will be more pronounced when the panel width increases or when the panel thickness decreases.
Oil canning is strictly an aesthetic concern, as it does not compromise the structural integrity or ability of the metal roofing. Oil canning can, however, affect the market value of the home. Regardless, many homeowners tend to be unhappy with the look, and would like to call in a roofer to fix the problem.
What Causes Oil Canning to Happen?
To put it simply, oil canning is caused by a difference in the stresses within the metal itself. As the sheets of metals attempt to relieve the stresses, they will buckle in different areas that cause the waviness to emerge. There are many different causes that can lead to the buildup of these stresses. They include:
- Metal coil production. The production of metal shingles begins with metal coil production. Stresses that are induced during the coil production, such as if the coil is longer in the middle of the strip, deviate from the side edge or is longer at the edges, lead to oil canning.
- Coil processing and panel fabrication. If stresses have already been introduced into the metal coils, then different processes in coil processing and panel fabrication can redistribute the stresses to different areas of the metal. For example, if a master coil is slit to make smaller ones, the stresses in the metal will be released and redistributed. This can lead to oil canning in the metal shingles.
- Misalignment in the support systems that hold the metal shingles up. This generally happens when the supporting frame is not flat against the metal shingles. Misalignment can also cause instability in the positioning of the metal shingles, which can allow for movement in the primary structure.
- Improper panel installation. Many problems can arise if the roofers are not experienced in metal roofing installation. For example, overdriving of fasteners is an extremely common problem that can create stresses to emerge in the panels. Metal roofing experts also need to account for thermal expansion and contraction, and install accordingly.
If your metal roofing shingles are exhibiting oil canning, it is important that the roofer performs a thorough analysis and examination in order to determine what the underlying problem may be. Unless the correct underlying problem is identified, proper repair cannot be performed.
How Can Oil Canning Be Prevented?
Due to the fact that oil canning is aesthetically displeasing, a lot of effort is spent on ensuring that preventive techniques are implemented. Do your due diligence in researching the conditions and properties of the metal shingles that you have chosen to make sure that they are able to minimize the chances of oil canning. Some properties to look for include:
- Thickness. Generally speaking, thicker metal shingles are less likely to exhibit oil canning since the shingles can absorb the stresses, and elastic buckling is not likely.
- Panel finish. By choosing metal shingles with a lower gloss, oil canning will be less perceptible. Low gloss finishes tend to be less reflective to make oil canning less obvious.
- Panel design. Keep in mind that the metal shingles will expand and contract with time, as well as the entire panel framing. Choose a panel design that is more forgiving of thermal stresses. Some panel designs have stiffening ribs added to them that can help prevent oil canning from happening.
Although oil canning does not affect the abilities and durability of the metal shingles, most homeowners are not happy with the overall look that they contribute to their home. If you are dealing with oil canning, then chances are that there were some issues in the metal shingle production or the installation. You will need to speak with a professional roofer or read more here in order to determine what the best solution may be for your situation.