Oil Canning and Flush Metal Wall Panels

Oil canning is a broad term in the world of metal panel products and is considered one of the most vexing issues facing metal panel installations. The Metal Construction Association (MCA) defines oil canning as a “visible waviness in the flat areas of metal roof and metal wall panels.” Oil canning, also known as elastic buckling or stress wrinkling, occurs in all types of metal panels. While it is a common concern, there are steps you can take to minimize the problem.

Here, we’ll focus specifically on oil canning/distortion with metal flush wall systems, which for MBCI products includes our FW Panels and Designer Series. The type of oil canning that occurs with flush wall systems is not caused by anything dealing with the product itself or with how it’s manufactured. Rather, it is a consequence of what installers are putting the metal panels on and how the installation is done.

Installers must verify the substructure is in frame to prevent oil canning of panels.
Installers must correct any out-of-plane areas of the substructure to prevent metal panels from oil canning.

The simplest way to explain the phenomenon is that if the substructure is out of plane, i.e., not in alignment, stresses are put onto the panels that will create an appearance of oil canning. After all, as the old adage goes, you only get out what you put in. In the case of flush metal wall systems, the panels will look no better than what they are put on top of. If the substructure is wavy, out of plane, up or down, in or out, that condition will affect the panels’ performance and appearance.

Certain tolerances will have an effect on the panels’ appearance. With MBCI’s FW and Designer panels, tolerances would be 1/4 inch and 20 feet outward (away from two attachment points) and 0 inch and 20 feet inward. This means that if panels are forced into an inverted convex position, they will show stress rippling or oil canning more severely than when they’re stretched over a concave position, i.e., there can be some tolerance outward but zero inward.

With these types of panels, the biggest concerns with oil canning/distortion are aesthetics, but performance problems are also of concern, including possible engagement or sealing of the side joints.

Minimizing Oil Canning/Distortion of Panels

Prior to installation, installers should be checking the substructure with string lines or lasers and correcting or shimming any areas that are out of plane, especially since oftentimes substructures, such as stud walls or structural walls that the metal panels are attached to, are installed by other trades. Metal panel installers need to scrutinize each aspect for alignment and then either correct or shim to bring it within tolerance and within plane.

As is true with any metal panel product, for best results, proper handling and installation go a long way towards preventing the problem of oil canning in the field.

To find out more on how to minimize oil canning on your MBCI metal wall panels, contact your local MBCI representative, and sign up for our newsletter to subscribe to our blog.

Spray Polyurethane Foam (SPF) Insulation on Metal Roof and Wall Panels

With building code compliance and sustainable building envelopes at the forefront in today’s marketplace, spray polyurethane foam insulation (SPF) applied to single skin metal roof and wall panels is an alternative to insulated metal panels with a manufacture-applied polyurethane foam core. SPF insulation improves a building’s energy efficiency and provides thermal, air and vapor barrier capabilities.

What Is Spray Polyurethane Foam (SPF) Insulation?

SPF insulation consists of isocyanate and polyol resin that is chemically combined and applied to surfaces using a spray gun. SPF insulation can be open cell or closed cell.  Open-cell foam provides insulation and air sealing for a building, but is water and vapor permeable. Closed-cell foam provides better insulation than open cell and also functions as an air barrier. Closed-cell foam differs from open cell in that it prevents water entry, minimizes moisture vapor permeability and decreases air leakage, making it the preferred insulation to apply to metal panels.

Spray Foam Insulation with Metal Panels
Spray Polyurethane Foam Insulation with Metal Panels. Image courtesy of Spray Polyurethane Foam Alliance

SPF insulation is well suited for use as interior insulation for metal wall and through-fastened metal roof panels. The traditional thermal insulation layer—one or two layers of batt insulation with a facer—has its intricacies; for example, compressed areas and difficulty taping seams at edges and penetrations for air barrier performance.  But because of SPF’s inherent physical characteristics and spray application method, SPF overcomes many obstacles.

8 Application and Safety Tips for SPF

Using SPF to fully insulate and seal a building with metal panels can have unintended consequences if the material characteristics and project parameters are not well thought out. The Metal Construction Association (MCA) recently conducted research with the Spray Polyurethane Foam Alliance (SPFA) and published their findings in a technical bulletin. It includes the following best practices and considerations for installing SPF.

Image courtesy of Spray Polyurethane Foam Alliance
  1. Utilize a certified foam spray technician to ensure the insulation meets the desired thickness, density and adhesion.
  2. Only apply SPF to clean, dry areas.
  3. SPF should not be used on standing seam metal roof panels because it may restrict the thermal movement of the panels, causing distortion.
  4. Follow a “picture frame” application technique, further detailed here, to prevent SPF from getting between girts and metal panels, causing deformation.
  5. Notify other contractors, including HVAC and electrical, to ensure necessary precautions are made.
  6. Follow building code requirements for fire protection because in some instances SPF may meet thermal barrier requirements.
  7. Prevent SPF chemicals from being drawn into a building’s ventilation system during and after installation. There may be a mandated wait time before other occupants can reenter the space.
  8. Consult with your metal panel manufacturer before applying SPF.

Read more recommendations and findings by the MCA by downloading their technical bulletin, Spray Polyurethane Foam Insulation on Interior Surfaces of Metal Panels, here.

How to Help Prevent Oil Canning

Oil canning is defined as the visible waviness in the flat portion of a metal panel.  Oil canning is a visual issue, not a weatherproofing or performance issue.  However, building owners will complain about waviness in metal panels on roofs, walls, and perimeter edge metal.  Edge metal and metal wall panels are more of a concern than low-slope metal panels because edge metal and wall panels are visible from the ground.  Steep-slope metal panels and shingles are also visible, so awareness of potential oil canning is important.

Oil Canning on a Metal Roof

What Causes Oil Canning?

Oil canning can happen when unwanted stresses are introduced at fasteners, clips, and over purlins and uneven substrates.  Over-driven fasteners, clips that are slightly misaligned relative to the clip/seam interface, and too much insulation between the purlins and panels can introduce these unwanted stresses.  A misaligned panel or edge metal clip, certainly after the seam or drip edge is crimped tight, will add stresses to metal panels and edge metal

Tips to Help Prevent Oil Canning

  1. Place clips correctly: Setting clips in the proper location for edge metal and metal panels (roof and wall) is critical.  The clip needs to fit into a panel seam without forcing the vertical seam out of plane.  The clip needs to be aligned correctly and sized appropriately to not compress the vertical portion of the seam.  Clips that secure edge metal need to be positioned correctly so that crimping the drip edge won’t twist or bend the edge metal.
    Although not highly visible, low-slope structural panels can oil-can at clip locations and where insulation is draped over purlins.  Compressed insulation at purlins can “push back,” adding stress to the panel and resulting in oil canning.
  2. Consider the roof color: Sometimes oil canning is inevitable.  The color of the metal or coating won’t really make a visual difference, but darker colors panels will heat up more in direct sunlight.  This may make oil canning worse in some cases.  However, striations and small ribs (which also add strength) may help prevent or hide oil canning.
  3. Choose a thick metal: Metal thickness matters, so specify metal that’s as thick as possible to avoid oil canning.  Thicker metals are stiffer, so they may resist deformation due to unwanted stresses.  This reduces the chance of oil canning in edge metal and wall panels, which are most commonly smooth-surfaced.

For more information on oil canning and its causes, see the Metal Construction Association’s white paper on the subject, which can be found at www.metalconstruction.org.

Consider these ideas on your next job.

Design to Your Client’s Mindset

Spring Fire Department Station 78

As an architect, when did you last hear your client say, “Money is no object?”  This happens … almost never!  More likely what you hear is “I want high quality for low cost.”  The challenge of the architect is to provide your client with high quality at a reasonable and appropriate price.  A large part of finding that balance is determining the values, goals and long-term perspective of your client.

If a building owner wants a metal roof, it’s likely they already have a reason why.  Perhaps their existing roof didn’t provide the service life they expected it to, or it was damaged disproportionately.  Or the building owner understands that a metal roof can last a really long time.  Or they like the look of a metal panel or metal shingle roof, with all the colors and shapes available.  As an architect, it is important to determine your client’s mindset.  In the end, the question comes down to, “How long will you own this building (or home)?”  And, although less common, a building owner may just want to build a high-end, long-lasting building no matter their desired length of ownership.

The large part of the cost of a metal roof, similar to other roof types, is the labor to remove the existing roof and install the new one.   Upgrading from a 24-gauge metal to 22-gauge metal is a minimal increase in material costs that is easily justifiable for the long term.  Metal thickness, coating type and thickness, and penetration and edge details are the areas where upgrades and enhancements occur.

Argue against value engineering.  Roofs certainly can be out of sight, out of mind to most owners, but building owners who are considering metal roof systems understand the concept of life-cycle analysis, whether they know it or not.  Overtly reinforce their long-term outlook to help ensure that high-end penetration details and edge details are designed and installed.  Look to the industry standards—SMACNA, NRCA—for details that will last the life of the metal panels.  Realize that metal panels don’t leak; joinery and flashings are the potential leak locations.  Upgrade the details to be of the highest quality.

Understanding the mindset of your client is critical to determining the level of design.  This is definitely a cost issue.  The “university” client thinks long term; the “developer” client thinks short term.  However, there is much middle ground that requires inquisitive discussion with an owner to determine his/her goals.  Ask the questions, and design a metal roof based on your client’s mindset.

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