Updated: September 16, 2013
The Metal Construction Association (MCA) defines oil-canning as: “perceived waviness in the flat areas of metal roofing and metal siding panels. Generally the period and amplitude of the wave depend on the continuous width of the flat.” Industry literature sometimes uses oil-canning synonymously with deflection, although this is a misnomer. Deflection may be indicative of genuine structural concerns, while oil-canning is at worst a visual annoyance. All general categories of metal panel are subject to oil-canning, so—while it is most commonly associated with roof sheets—wall panels, insulated metal panels, metal composite material and flashing have all been observed to oil-can.
The MCA cites a list of possible causes of oil-canning (e.g. lapses in production, fabrication or installation), but its conclusion, simply stated, is that “oil canning is an inherent part of light gauge cold formed metal products.” Some design factors that contribute to this visual phenomenon are:
- Lighter gauges in lieu of heavier gauges
- Larger flat sections in lieu of smaller sections (including longer panels in lieu of shorter panels)
- Insufficient panel supports or type of support
- Direct sun in lieu of indirect sun (also, vertical material exhibits more oil-canning than does soffit material, and metallic, mica or anodized finishes exhibit it more than opaque finishes do)
- Darker colors in lieu of brighter colors
- Similarly-colored adjacent material in lieu of contrasting adjacent material
- Smooth textures in lieu of embossed textures
Whether or not oil-canning is a cause for material rejection is a matter for contract documents to decide, therefore it is imperative for owners and architects to understand the nature of the specified material prior to its procurement.
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