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 17
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method.
Details, formula, and sources
ScopeRAKES 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.
Formula or tableslope 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)).
Source and editionRoof takeoff geometry - no standard claimed; the eave-under / rake-over installation convention is manufacturer installation guidance.
Free accessGeometry; drip-edge installation direction is published in every manufacturer's instructions.
What governsEstimate. AHJ and licensed professional govern.
API field nameseave_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