US Patent 11913235 Synthetic mechanically attached roof underlayment system

An underlayment system for a roof structure including underlayment material disposed in covering relation to a roof deck and a plurality of mechanical fasteners disposed and structured to interconnect the underlayment material to the roof deck. Each mechanical fastener includes an outer plate, an under plate and a connector penetrating through both the outer plate and under plate in secured relation to the roof structure. The under plate is disposed and structured to sealing engage the connector penetrating there through. The under plate is further disposed in engagement with an undersurface of said outer plate and beneath and in segregating relation between an outer peripheral edge of the outer plate and the underlayment material.