Flashing & coil · Guide 3 of 5 · 3 min readUpdated
Calculate sloped and gable flashing cuts
Choose a repeatable way to cut tapered flashing, preserve peaks within a piece, and keep fabrication marks tied to the installed coverage.
Use scheduled tapers when the profile really repeats
For a straight measured slope, calculating the height at each coverage station can make a run of tapered blanks consistent. If the building edge is irregular, field templates or individual checks may be more useful than extending a perfect line across it. Decide which situation you actually have before batching cuts.
A gable adds a change of direction. A piece that crosses the peak must retain that high point, even when both its side edges are lower. The formed seam adds another distinction: a height at an installed coverage edge is not automatically a mark on the raw edge before folding.
Example: an older gable with an uneven edge
Use the schedule to organize the pieces, then compare intermediate field measurements with the assumed straight slopes. If the edge bows or steps, record that shape before fabrication. Cutting an entire batch from only the two ends and peak can faithfully reproduce a profile the building does not have.
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.
Use coverage stations before developing the folds
The schedule heights describe the wall profile at the beginning and end of each covered interval. Folded locks and inserted material need their own developed profile; those coverage heights are not automatically raw-edge cut marks through a fold. Add required bend-height allowance before allocating a blank.
In a 100-inch run with a centred 20-inch peak and 10-inch ends, the panel covering stations 34–67 inches contains the peak. Mark the peak 16 inches from that coverage start. Connecting only the two endpoint heights would cut away the required peak.
Technical references
Confirm the current product literature and requirements for the material and assembly being installed.