Metal Roofing Applications

Underlayment is the first layer of material laid prior to metal roofing panels. Roof underlayment plays a vital role in any roofing application. Its primary purpose is to act as a water-shedding layer, providing a secondary layer of protection from weather, shielding the roof deck during construction and is often required for warranty adherence as well as roofs that must meet Underwriter’s Laboratory (UL) fire ratings.

There are four basic types of underlayment that can be used under metal roofing coverings:

Slope Limitations:  On low-slope roofs, which include 2:12 up to 4:12 pitch, felt courses should overlap a minimum of 19 inches. This provides a double layer of underlayment across the entire roof.

On steep-slope roofs (4:12 and steeper), the upper courses of felt underlayment should overlap lower courses by at least 2 inches.


Fastening: Atlas recommends that all underlayment be mechanically fastened using plastic cap fasteners.

Atlas recommends the use of any of the above underlayments to be used under metal roofing.

For highest overall performance Atlas recommends the use of:

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