Use this 3 part SimpleSpecs™ master specification to specify custom-fabricated sheet metal components flashing and trim, gutters, downspouts, copings, facias, and through-wall scuppers, which can be fabricated from a variety of metals.
Sheet metal flashing and trim can be fabricated from a variety of metals including galvanized steel, precoated galvanized steel, aluminum-zinc alloy coated steel, precoated aluminum-zinc alloy coated steel, stainless steel, copper, copper-clad stainless steel, and aluminum. Other metals are also available and can be added to this section.
Sheet metal is difficult to make watertight due to its high coefficient of thermal expansion. For this reason, sheet metal flashings should be placed over a layer of flexible flashing or weather barrier.
Sheet metal is susceptible to waviness in the metal as the metal expands and contracts referred to as oil canning. Oil canning is primarily an aesthetic issue and is worse on wide, flat surfaces. Detailing sheet metal to allow for expansion and contraction will minimize oil canning. In no case should the metal be fastened in a manner that prevents movement. Increasing the gage of the metal has little effect on oil canning.
Refer to the following for assistance in selecting and detailing sheet metal roofing:
– Architectural Sheet Metal Manual by the Sheet Metal and Air Conditioning Contractors National Association (SMACNA) are available line at smacna.org,
– Technical resources by the Copper Development Association (CDA) are available at copper.org
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