Low slope roofing insulation board installed over steel decking should be applied in a MINIMUM of two layers

While proper drainage is crucial in roofing systems, the application of insulation in multiple layers does not directly relate to drainage capabilities. Instead, drainage is typically managed through the roofing design and slope, rather than the number of insulation layers.

There is no specific requirement linking the number of insulation layers to a thickness of 2 inches. The necessity for multiple layers is based on minimizing thermal breaks and gaps rather than solely on the thickness of the insulation.

The method of fastening does not dictate the need for multiple layers of insulation. Mechanical fastening may be applicable in single or double-layer installations; however, the rationale for applying multiple layers focuses on minimizing thermal breaks, regardless of the fastening method.