Valley Flashing Takeoff (Metal, Pieces, Ice Barrier)
step-flashing-count is roof-to-wall, ice-barrier-coverage does eaves and calls valleys a separate add, and hip-valley-rafter gives framing but no metal. A valley is the longest run on the roof for its plan dimension because it goes diagonally AND uphill: the multiplier carries 288 under the radical where a common rafter carries 144, so a 12-ft plan run at 6:12 is exactly 18 ft of valley against 13.4 ft of common. Ordering off the plan comes up badly short.
Formula and source
valley multiplier = sqrt(pitch^2 + 288)/12 (the framing-square 17-inch rule) against a common rafter's sqrt(pitch^2 + 144)/12; valley length = plan run x multiplier; pieces = ceil(LF x (1 + waste)/(stock - lap/12)); metal area = LF x width/12.
Valley geometry by the framing-square 17-inch rule - public geometry, no table reproduced.
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