Roof Drip Edge Rake / Eave Split and Piece Count
roofing-squares returns drip edge as a bare passthrough of the perimeter, which hides the thing that matters.
Example
You enter
- Total eave length (ft, plan) 80
- Horizontal run of ONE rake (ft, plan) 14
- Number of rakes 4
- Roof pitch (rise per 12) 6
- Stock length (ft) 10
- Lap at each joint (in) 2
- Waste (%) 10
You get
- Slope factor 1.1180
- Eave (LF) 80
- Rake (LF) 62.6099
- Rake slope gain (LF) 6.6099
- Total (LF) 142.61
- Effective piece (ft) 9.83333
- Pieces 16
Details, formula, and sources
RAKES run up the slope and eaves do not. Measured off the plan, a 6:12 rake under-orders by 12% - four 14-ft rakes are 62.6 ft of metal, not 56. They are also different profiles installed opposite ways (eave under the underlayment, rake over), so they are counted separately, and pieces are figured on the stock length minus the lap.
slope factor = sqrt(1 + (rise/12)^2); rake LF = rake count x plan run x slope factor; eave LF = plan eave length; pieces = ceil(LF x (1 + waste) / (stock - lap/12)).
Roof takeoff geometry - no standard claimed; the eave-under / rake-over installation convention is manufacturer installation guidance.
Geometry; drip-edge installation direction is published in every manufacturer's instructions.
Estimate. AHJ and licensed professional govern.
Field names used by the API: eave_length_ft, rake_run_ft, rake_count, pitch_rise_per_12, stock_length_ft, lap_in, waste_pct, slope_factor, eave_lf, rake_lf, rake_slope_gain_lf, total_lf, effective_piece_ft, pieces
- Slope factor on rakes only rakes take sqrt(1 + (rise/12)^2); eaves are horizontal and take plan lengthroof geometry
- Effective stick length stock length minus the lap at each jointtakeoff practice
- Profiles differ eave drip installs under the underlayment, rake drip over; counted separatelymanufacturer installation instructions