Flashing & coil guide · 6 min read
Calculate sloped and gable flashing cuts
Build a piece-by-piece cut schedule for a single slope or gable without underestimating blanks at the high point.
Treat height as a position along the wall
On a straight slope, flashing height changes steadily from one end to the other. The calculator interpolates the height at both edges of each covered piece so the blank can include the taller edge.
Height at position = start height + (end height − start height) × position ÷ run
Handle a peak inside a piece
A gable should be treated as one continuous profile with a left end, peak, and right end. When the peak falls inside a piece rather than on a joint, the required blank must reach the peak height even if both piece edges are lower.
Do not split the gable into two unrelated runs unless the installation actually has a centre seam with its own lap. Doing so can double-count coverage or miss the peak-crossing blank.
Label the installation direction
- Choose a clear start end and keep schedule numbers consistent.
- Mark each blank with piece number, low edge, high edge, and orientation.
- Allow for the seam or lap direction required by weather exposure and the assembly.
- Recheck the field run and peak location before cutting the final pieces.