A drip edge is a bent metal strip that the 2021 International Residential Code (IRC) requires at the eaves and rake edges of shingle roofs, overlapped at least 2 inches, extended at least 1/4 inch below the sheathing, and fastened at not more than 12 inches on center (Section R905.2.8.5). It sheds water clear of the fascia and roof deck edge.
Drip edge, also sold as edge metal or eave flashing, is a thin formed-metal flashing that wraps the roof deck edge: part lies flat on the deck and part hangs down over the edge. Its job is to break the path water takes by clinging to the underside of the deck and rotting the edge boards.
Key facts
- Drip edge must be provided at the eaves and rake edges of shingle roofs (2021 IRC Section R905.2.8.5).
- Adjacent segments of drip edge must overlap not less than 2 inches (2021 IRC Section R905.2.8.5).
- Drip edge must extend not less than 1/4 inch below the roof sheathing and up onto the roof deck not less than 2 inches (2021 IRC Section R905.2.8.5).
- Drip edge must be mechanically fastened to the roof deck at not more than 12 inches on center (2021 IRC Section R905.2.8.5).
- Underlayment goes over the drip edge along eaves and under it along rake edges (2021 IRC Section R905.2.8.5).
- Fasteners must be those specified in 2021 IRC Section R905.2.5: roofing nails of galvanized steel, stainless steel, aluminum or copper.
Is drip edge required by code?
Yes, for shingle roofs. Section R905.2.8.5 of the 2021 IRC reads as a single requirement: a drip edge shall be provided at eaves and rake edges of shingle roofs. It sits within the asphalt shingle provisions, under the flashing section R905.2.8, so it is a flashing component and not a decorative trim.
Local adoption matters. The code edition and any amendments your jurisdiction has adopted govern the project, and the shingle manufacturer's installation instructions are part of what the code requires (Section R905.2.8 says flashing for asphalt shingles must comply with the section and the shingle manufacturer's approved instructions).
What are the 2021 IRC drip edge requirements?
Section R905.2.8.5 contains five requirements: overlap, projection below the sheathing, return onto the deck, fastening, and order relative to underlayment.
2021 IRC Section R905.2.8.5: drip edge requirements for shingle roofs.
| Requirement | Value | Where it applies |
|---|---|---|
| Location | Eaves and rake edges | All shingle roof edges |
| Overlap of adjacent segments | Not less than 2 inches | End to end along the edge |
| Extension below roof sheathing | Not less than 1/4 inch | Hanging leg |
| Extension back onto roof deck | Not less than 2 inches | Flat leg |
| Fastening | Mechanical, not more than 12 inches on center | Into the roof deck |
| Fastener type | As specified in Section R905.2.5 | Roofing nails |
| Underlayment order | Over drip edge at eaves, under at rakes | Eave versus rake |
The code does not set a metal gage, a minimum thickness for drip edge, or a profile, such as T-style or L-style. Where a manufacturer lists a metal or finish, follow that.
What fasteners does drip edge need?
Section R905.2.8.5 points to Section R905.2.5. That section calls for galvanized steel, stainless steel, aluminum or copper roofing nails, with a minimum 12-gage (0.105 inch) shank and a minimum 3/8 inch diameter head, long enough to penetrate through the roofing materials and at least 3/4 inch into the roof sheathing. Where the sheathing is thinner than 3/4 inch, the fasteners must go through it. Nails of a different metal from the drip edge can corrode where they touch, so match the metals.
What is the difference between eave and rake drip edge?
Eave drip edge runs along the bottom edge of the roof where water leaves the deck, and rake drip edge runs up the sloped gable edges. The metal is often similar, but the underlayment order is reversed.
How drip edge relates to underlayment at eaves and rakes under 2021 IRC Section R905.2.8.5.
| Edge | Where water goes | Underlayment | Drip edge position |
|---|---|---|---|
| Eave | Flows off into gutter or drip line | Installed over the drip edge | Drip edge lies on the deck first |
| Rake | Wind-driven water pushes up from the side | Installed under the drip edge | Drip edge lies on top of underlayment |
At the eave, the underlayment laps over the metal so water running down the roof is carried over the metal and off the edge, not behind it. At the rake, the metal goes over the underlayment so the edge of the felt or synthetic sheet is covered and cannot be lifted by wind. For the roof edge terms, the parts of a roof page labels eave, rake, fascia and soffit.
What order does everything go on?
The code fixes two relationships (eave: underlayment over metal; rake: underlayment under metal). The rest of the sequence follows from them.
- Confirm the deck is solidly sheathed. Asphalt shingles must be fastened to solidly sheathed decks (Section R905.2.1).
- Fasten the eave drip edge to the deck, overlapping segments at least 2 inches and nailing at not more than 12 inches on center.
- Where an ice barrier is required, install it from the lowest edge. See the next section.
- Roll the underlayment over the eave drip edge, working up the slope.
- Lay the rake drip edge over the underlayment and fasten it at not more than 12 inches on center.
- Install flashing, valley linings and then the shingles. Valley and wall flashing are covered in roof flashing and roof valley.
How does drip edge interact with ice barrier and underlayment?
The ice barrier and underlayment follow the same over-at-the-eave rule. The code text only states the order for underlayment, so where a self-adhering sheet replaces normal underlayment at the eave, follow the manufacturer's instructions.
Where an ice barrier is required for an area with a history of ice at the eaves, it consists of at least two layers of underlayment cemented together, or a self-adhering polymer-modified bitumen sheet used in place of normal underlayment. It extends from the lowest edge of all roof surfaces to a point not less than 24 inches inside the exterior wall line. On roofs 8:12 or steeper, it must also reach not less than 36 inches measured along the slope from the eave edge (Section R905.1.2). The ice and water shield guide covers when it is required.
Underlayment itself follows Section R905.1.1 and Tables R905.1.1(1) to (3). For asphalt shingles, slopes from 2:12 up to 4:12 need two layers, and slopes of 4:12 or greater one layer. Fastener patterns are in Table R905.1.1(3).
Does a metal roof need drip edge?
The Chapter 9 text for metal roof panels (Section R905.10) covers deck, slope, attachment and underlayment, and does not repeat the shingle drip edge rule. Panel systems have their own eave and rake trim, and the manufacturer's installation instructions and approved details control. Do not apply the 2 inch overlap and 12 inch nailing figures to a metal panel roof unless the panel manufacturer says the same.
For reference, the code sets minimum slopes for metal roof panels in Section R905.10.2: 3:12 for lapped, nonsoldered-seam roofs without applied lap sealant, 1/2:12 with applied lap sealant, and 1/4:12 for standing-seam systems.
Where do drip edge mistakes happen?
Most failures come from order and edge conditions, not from the metal itself.
- Underlayment under the eave metal. This lets water run behind the drip edge and onto the fascia. Section R905.2.8.5 requires underlayment over the drip edge at eaves.
- Underlayment over the rake metal. This leaves the underlayment edge exposed to wind. The code requires it under at rakes.
- Short laps. Segments overlapped less than 2 inches fall short of the section.
- Too little projection. A drip edge that does not extend 1/4 inch below the sheathing does not break the water's path off the deck edge.
- Widely spaced nails. Fastening is limited to 12 inches on center.
- Gutter conflicts. The code does not set gutter details, so coordinate with the gutter installer before the metal goes on.
Showing roof edge metal on a plan
Drip edge is a covering detail, so it belongs in the roof section or edge detail, not on the framing plan. A roof framing plan shows the overhang and rake framing the metal will sit on. See roof framing plan. Framing Plan is a preliminary drawing aid: it draws joist layouts, beams and openings and exports PNG, PDF and DXF, and does not check code or select roof coverings. It works in millimeters. The adopted code edition and local amendments govern.
Summary
For shingle roofs, 2021 IRC Section R905.2.8.5 requires drip edge at eaves and rakes, overlapped at least 2 inches, extending at least 1/4 inch below the sheathing and at least 2 inches onto the deck, fastened at not more than 12 inches on center. Underlayment goes over the metal at the eave and under it at the rake. Metal roofs follow the panel manufacturer's trim details.
Open the framing studio to draw the roof edge and overhang framing in a preliminary plan before you send it to your designer or plan reviewer.