Metal Roofing Specifications

Liabilities and Precautions

• As with any construction project, there are risks associated with roofing. Creating a metal roof has the added burden of being a project that uses as its medium a more inflexible, more unforgiving material than other roofing options such as asphalt or wood shingle. To that end, the specifications for metal roof installation may be somewhat more austere. According to Universal Steel, installers must carry a minimum liability amount for each loss. (Reference 1) The foreman must be trained in installation with a minimum of five projects of similar size and scope. Also, a third-party consultant must supervise and inspect the overall installation.

Load Specifications

• Like all roofs, metal roofs must meet certain load requirements. Put another way, there are certain amounts of weight they must be able to hold, whether from live loads--those that are temporary like rain or wind--or dead loads--like gutters and other structural components. According to Universal Steel, live load specifications state that "the panels and concealed anchor clips shall be capable of supporting a minimum uniform live load of 20 psf," while the dead load specifications call for the roof to be able to support all the necessary structural components. (Reference 1)

Material Integrity

• The specifications for any type of metal roof, whether it is copper, tin, aluminum or steel, require that it be able to withstand temperature fluctuations. Like wood, metal expands, and specifications for metal roofs require that this be considered in the design. According to McGraw Hill Construction, "Because thermal expansion and contraction affects all materials to some extent, structural panels and flashing must be designed to accommodate that same expansion. It is worth noting that steel expands 1 inch per 100 feet, given a 100-degree temperature change. Aluminum will expand 2 inches per 100 linear feet given the same 100-degree temperature change. Panels designed for a structural roofing application should also be UL-90 rated for wind resistance" (Reference 3).