Mechanically Attached Single-Ply Fastener and Plate Takeoff
The line membrane-roof-takeoff ends on: "Fasteners, plates, and cover tape are taken off separately." On a mechanically attached system the fasteners go through the SIDE LAP and the next sheet welds over them, so the fastener rows ARE the seams -- and the rows land on the USABLE width after the lap, not the nominal roll width, which is the undercount to avoid. An 8,000 sq ft roof on 10 ft sheets with a 6 in lap has 842 LF of seam; at 12 in on center in the field and 6 in in the perimeter and corner zones over a quarter of that length, 1,054 fasteners and plates, 1,107 with waste, about 13.8 per square. Cover tape is counted only when fasteners land in the FIELD of a sheet instead of a welded lap. The spacings are NOT built in -- on-center spacing and the zone widths come from the wind-uplift calculation and the assembly\u0027s FM or UL approval, so they are inputs. A takeoff, not an uplift design.
Formula and source
usable width = roll width - side lap; seam length = area / usable width (delegated to membrane-roof-takeoff); perimeter seam = seam x share; field seam = seam - perimeter; fasteners = ceil(length x 12 / on-center spacing) for each zone; total = ceil(sum x (1 + waste)); plates = fasteners; cover tape = ceil(seam x (1 + waste)) only when fasteners land in the field of a sheet; density = fasteners / (area / 100).
Mechanically attached single-ply geometry. The rows follow the seams because the fasteners pass through the side lap and the succeeding sheet is welded over them. Spacings and zone extents are project values from the wind-uplift calculation and the assembly approval, not from this tile.
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