A 40-foot gable roof needs more drip edge than its edge length suggests. This worked example turns two 40-ft eaves and four 24-ft rakes into a checked 25-stick order, with every extra stick accounted for.
What does this example roof measure?
A simple rectangular gable roof has 2 eaves along the low edges and 4 rakes running up the gable ends. The rake runs are measured along the roof slope, not along the ground.
| Run | Count | Length each | Total |
|---|---|---|---|
| Eaves | 2 | 40 ft | 80 ft |
| Rakes | 4 | 24 ft | 96 ft |
| Total edge | 6 runs | 176 ft |
The roof measurement guide shows how to lay out and record each run. Pieces do not span corners, so every run is converted to sticks on its own.
How many sticks does one run need?
Drip edge sells in 10-ft sticks. Adjacent sticks on the same run need at least a 2-in overlap at every joint under IRC R905.2.8.5. The piece count for one run is the run length minus one overlap, divided by the stick length minus one overlap, rounded up:
Sticks per run = ceil((run length - 2 in) / (120 in - 2 in))
40-ft eave run. 480 in of run: (480 - 2) / 118 = 4.0508, which rounds up to 5 sticks.
24-ft rake run. 288 in of run: (288 - 2) / 118 = 2.4237, which rounds up to 3 sticks.
Four sticks would cover the eave at 474 in of installed coverage, 6 in short of 480 in. The fifth stick is not waste; it is the only way to finish the run.
What is the whole-roof stick count?
| Run | Runs | Sticks per run | Sticks total |
|---|---|---|---|
| Eaves | 2 | 5 | 10 |
| Rakes | 4 | 3 | 12 |
| Roof total | 6 | 22 |
Why does dividing the total edge length give the wrong answer?
Dividing 176 ft by 10 ft gives 17.6, which rounds to 18 sticks. That shortcut assumes sticks span corners and laps cost nothing. Both assumptions fail on the roof.
| Method | Sticks | What it misses |
|---|---|---|
| Whole perimeter divided by 10 ft | 18 | Lap joints and per-run rounding; 4 sticks short |
| Per-run count with 2-in laps | 22 | Cut waste and spare pieces |
| Per-run count with 10% allowance | 25 | Nothing: this is the order total |
Sixteen lap joints at 2 in each consume 32 in, about 2 ft 8 in of paid material. Corner rounding costs the other 4 sticks: a run that needs 5.05 sticks still needs 5 sticks, and the 0.05 remainder cannot come from the next run's leftover.
How much extra belongs in the order?
Add 10% to the 22-stick count on a roof this simple: 22 x 1.10 = 24.2, which rounds up to 25 sticks. That allowance covers mitered corners, cut-offs, kinked pieces, and one re-cut.
The 10 to 15% allowance is a trade planning habit, not a code value. No building code sets a waste percentage. The ordering and waste guide explains when the 15% end of the range fits better.
How do you check the answer?
Check 1: coverage on every run. Installed coverage is the stick count times 120 in, minus one 2-in lap per joint. A 40-ft eave covered by 5 sticks gives 600 - 8 = 592 in, which clears 480 in. A 24-ft rake covered by 3 sticks gives 360 - 4 = 356 in, which clears 288 in. The final offcut is 112 in (9 ft 4 in) on each eave and 68 in (5 ft 8 in) on each rake.
Check 2: the material ledger balances. Twenty-five 10-ft sticks buy 250 ft of material. Add the recorded edge (176 ft), the lap loss (2.67 ft), the offcuts (41.33 ft), and the 3 spare sticks (30 ft):
176 + 2.67 + 41.33 + 30 = 250 ft
Every foot of the 250 ft bought is named. When the ledger does not balance, one step above was skipped.
Which mistakes does this example prevent?
- Dividing total edge length by the stick length and ordering the result.
- Copying one run's stick count to a run of a different length.
- Assuming offcuts will cover another run, when pieces cannot span corners.
- Treating the waste allowance and the lap overlap as the same correction.
Sources and scope
- ICC, 2018 IRC Chapter 9, R905.2.8.5: drip edge required at eaves and rakes of shingle roofs; joints overlapped not less than 2 in; fastened to the deck at not more than 12 in on center. Retrieved 2026-10-20.
- EngineerFix, "How to Calculate How Much Drip Edge You Need": 10-ft standard stick length and 10 to 15% waste factor practice. Retrieved 2026-10-20; used for product facts, not code proof.
- Roofmaxx, "A Guide to Drip Edge Sizes for Residential Roofs": 10-ft sections with one extra section for overlaps. Retrieved 2026-10-20; used for product facts, not code proof.
Scope: the worked example computes a stick count for the stated roof dimensions, stick length, and code-minimum overlap. It does not establish code compliance for a specific jurisdiction, product choice, price, or fall-protection planning. Material and installation rules live in the linked materials guide and mistakes guide.
Review responsibility: Saleem Sial owns the published calculation, source, and editorial checks. Waseem Sial, External Reviewer and Engineer, remains listed for ongoing external review; no completed external-review date is claimed.
Next, use the drip edge measurement guide to record runs on your own roof, or return to the Roofing Calculators hub.
