Metal slope requirements

Structural metal panel roof systems have become a common choice for low-slope roofing applications. These systems are an appealing alternative to using low-slope roof membrane systems for several reasons. For example, structural metal panels have the strength and capability to span structural members, therefore eliminating the need for a roof deck. In addition, structural metal panel roof systems can be attractive and provide long-lasting, cost-effective service lives.

However, roof system designers who specify structural metal panel roof systems need to be aware of varying recommendations for minimum roof slope by different sectors of the construction industry.


The NRCA Roofing and Waterproofing Manual, Fifth Edition, states the minimum slope for structural metal panel roof systems should be 1/2-in-12 (2.4 degrees). This recommendation conflicts with some manufacturers who list 1/4-in-12 (1.2 degrees) as an acceptable minimum slope.

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