9.1 Edge Metal & Drip Edge: Code Rules (IBC 1507.2.8.3 / IRC R905.2.8.5), FORTIFIED Upgrades & ES-1 Edge Securement

Edge Metal Flashing: Drip Edge, Gutter Aprons & Edge Securement

Roof edges are the most vulnerable part of a steep-slope roof. Wind pressures are highest at eaves, rakes, and corners. Once wind gets under the edge, it can drive rain under the shingles, peel back the underlayment, and start a progressive peel of the roof covering. Drip edge sheds water off the deck edge and away from the fascia, and it stiffens and protects the edge of the roof covering. Under the IBC and IRC as adopted in the Louisiana State Uniform Construction Code (LSUCC), drip edge is required on asphalt shingle roofs.

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1. The Code Rule: IBC 1507.2.8.3 and IRC R905.2.8.5

The PSI Louisiana Residential Roofing exam references the 2021 IBC, which states the rule in Section 1507.2.8.3:

IBC 1507.2.8.3 Drip Edge: "A drip edge shall be provided at eaves and rake edges of shingle roofs. Adjacent segments of the drip edge shall be lapped not less than 2 inches (51 mm). The vertical leg of drip edges shall be not less than 1 1/2 inches (38 mm) in width and shall extend not less than 1/4 inch (6.4 mm) below sheathing. The drip edge shall extend back on the roof not less than 2 inches (51 mm). Underlayment shall be installed over drip edges along eaves. Drip edges shall be installed over underlayment along rake edges. Drip edges shall be mechanically fastened at intervals not greater than 12 inches (305 mm) on center."

The 2021 IRC R905.2.8.5, used for one- and two-family dwellings, has the same laps, 1/4-inch projection, 2-inch flange, eave and rake sequence, and 12-inch maximum fastener spacing, using the shingle fasteners of R905.2.5.

The Numbers to Memorize

How It Is Enforced

Missing drip edge at an eave or rake, the wrong lap order, or fasteners spaced wider than 12 inches are code deficiencies an inspector can cite (permits and inspections are covered in Chapter 1). Programs such as FORTIFIED set stricter rules (Part 5 below and Section 5.3).

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2. Sheet Metal Material Specifications and Gauges

Edge metal must survive decades of sun, humidity, and salt air.

Code Minimums for Flashing Metal

• IBC 1503.2.1 and IRC R903.2.1: where flashing is metal, it must be corrosion resistant and at least 0.019 inch thick (No. 26 galvanized sheet).
• IBC 1507.2.8.1: base and cap flashing for asphalt shingles must be corrosion-resistant metal of nominal 0.019-inch thickness. Base flashing may instead be mineral-surfaced roll roofing weighing at least 77 pounds per 100 square feet.

Common Edge Metal Materials

• Galvanized Sheet Steel: ASTM A653 with a G90 zinc coating is the usual specification, in 26 gauge or heavier. Lighter 28- or 30-gauge products bend during installation and fall below the 0.019-inch flashing minimum.
• Aluminum: ASTM B209 sheet, commonly about 0.019 to 0.032 inch for drip edge. Open valley linings of aluminum must be at least 0.024 inch (IBC Table 1507.2.8.2).
• Copper: cold-rolled copper, ASTM B370, 16 ounces per square foot (about 0.0216 inch). Use copper or compatible fasteners.
• Stainless Steel: used on severe salt-exposure sites near the Gulf.
• Coastal fasteners: FORTIFIED requires hot-dip galvanized or stainless steel fasteners and connectors within 3,000 feet of saltwater (Section 5.3).

Galvanic Corrosion Mitigation

Roofing contractors must prevent galvanic corrosion caused by coupling electrochemically dissimilar metals. Direct contact between aluminum drip edge and copper gutters, or between galvanized steel flashing and copper nails, speeds corrosion in Louisiana's humid, salty air. Fasteners must match or be galvanically compatible with the flashing:

• Galvanized steel edge metal -> Hot-dipped galvanized steel roofing nails.
• Aluminum edge metal -> Aluminum or stainless steel nails, or hot-dipped galvanized nails where the manufacturer allows.
• Copper edge metal -> Copper or compatible (bronze or stainless) nails.
• Treated lumber contact: copper-based preservatives such as ACQ and copper azole corrode aluminum and plain steel. Wood-treatment and flashing manufacturers call for a separation layer, such as self-adhered membrane or felt, or a compatible metal.

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3. Profile Anatomy: Drip Edge vs. Gutter Apron

Sheet metal flashings for roof perimeters are bent into specialized geometric profiles designed to optimize water discharge, break surface tension, and prevent wind-driven blow-in.

          STANDARD DRIP EDGE (T-STYLE / L-STYLE)                 GUTTER APRON PROFILE

          <──────── 2" to 3" Flange ────────>                 <───── 2" to 3" Flange ─────>
          ===================================                 ============================
                                            ║                                             ║
                      Roof Deck Substrate   ║                                             ║
                                            ║                                             ║
                                  Vertical  ║                                   Vertical  ║
                                  Face Leg  ║                                   Face Leg  ║ 2-1/2" to 3"
                                 (1-1/2")   ║                                  (Angled)   ║ (Drops into
                                            ║                                             ║  Gutter)
                           Kicked-Out Hem   ║<── 1/4" Gap                                 ║
                                     ───────╝    from Fascia                              ║
                                       /                                                  ║
                                      / 30°-45° Kick                                      ║
                                     o Hemmed Drip Edge                                   o Hemmed Apron

Anatomy of Drip Edge Flashings

1. Horizontal Roof Flange: Rests flat on the roof deck and extends back at least 2 inches (code). Wider flanges make room for staggered nailing.
2. Vertical Drop Face: Runs down the fascia or rake trim. The IBC requires it to be at least 1-1/2 inches and to extend at least 1/4 inch below the sheathing.
3. Kicked-Out Drip Hem: The bottom edge of the vertical face is angled outward and usually finished with a folded hem. The hem adds structural rigidity to the metal strip and forces descending water droplets to break surface tension and drop cleanly away from the building rather than clinging to the fascia wood.

Gutter Apron Flashing Mechanics

A gutter apron is an alternative edge metal profile installed specifically along eave edges equipped with exterior gutters:

• Extended Vertical Drop: Unlike standard drip edge that has a sharp 90-degree corner and short drip kick, a gutter apron features a deeper vertical drop (2-1/2 to 3-1/2 inches) angled slightly outward to match the slope of the fascia board.
• Direct Gutter Discharge: The extended drop leg hangs inside the back of the gutter, so water that runs down the metal lands in the trough instead of behind the gutter.

4. The Critical Installation Sequence: Eaves vs. Gable Rakes

The single most critical exam concept and field installation rule governing edge metal is the relationship between the drip edge and the roof underlayment. The sequence differs completely between eaves (horizontal drainage edges) and rakes (sloping gable edges).

                  EAVE INSTALLATION SEQUENCE                  RAKE INSTALLATION SEQUENCE
                  (Water-Shedding Hierarchy)                  (Wind-Uplift & Blow-In Defense)

          [ Course 1: Asphalt Shingles ]              [ Course 1: Asphalt Shingles ]
                        │                                           │
                        ▼                                           ▼
          [ Course 0: Starter Shingle Strip ]         [ Course 0: Starter Shingle Strip ]
                        │                                           │
                        ▼                                           ▼
          [ Underlayment / Ice & Water ]              [ EDGE METAL DRIP EDGE ] <── Over Underlayment
                        │ (Laps OVER Metal)                         │
                        ▼                                           ▼
          [ EDGE METAL DRIP EDGE ]                    [ Underlayment / Ice & Water ]
                        │ (Installed First)                         │ (Lapped to Edge First)
                        ▼                                           ▼
          [ Bare Structural Wood Deck ]               [ Bare Structural Wood Deck ]

A. Eaves Installation Protocol (Underlayment OVER Drip Edge)

Along the horizontal eaves of the roof, the primary hazard is water draining downward across the roof plane under gravity:

1. Step 1: The bare wood roof deck is cleaned, inspected, and verified flush.
2. Step 2: The drip edge metal is applied directly to the bare wood deck sheathing along the entire eave length before any underlayment is unrolled.
3. Step 3: The roof underlayment (synthetic underlayment, #30 felt, or ASTM D1970 self-adhering membrane) is installed OVER the horizontal metal flange of the drip edge.
4. Hydraulic Principle: If water bypasses the shingles at the eave, it flows down across the waterproof underlayment, transitions seamlessly onto the metal flange of the drip edge, and discharges safely into the gutter. If the drip edge were placed over the underlayment at the eave, runoff would hit the top edge of the metal flange and seep directly beneath the underlayment onto the wood deck.

B. Gable Rake Installation Protocol (Drip Edge OVER Underlayment)

Along the sloping rake edges (gables), the hydraulic dynamics are reversed. Gravity water flows parallel to the rake, while the primary threat is lateral wind-driven rain driving inward from the gable end:

1. Step 1: The roof underlayment is rolled completely to the gable rake edge, trimmed flush with the outer edge of the roof deck sheathing, and fastened.
2. Step 2: The drip edge metal is installed OVER the underlayment along the rake slope.
3. Step 3: The starter shingle strip and shingles are applied over the rake drip edge flange.
4. Wind and Water Principle: Placing the rake drip edge over the underlayment clamps the outer edge of the underlayment to the deck. If lateral wind drives rain under the rake shingles, the water hits the upper face of the underlayment and drains down slope. If underlayment were placed over the metal at the rake, crosswinds could catch the underlayment edge, peel it open, and channel water straight to the bare sheathing.

FORTIFIED exception at eaves: A FORTIFIED roof has a sealed deck under the underlayment, so FORTIFIED puts the drip edge over the underlayment at eaves too and seals the eave with flashing cement or a self-adhered starter (Part 5). Know both answers: the code answer at eaves is underlayment over drip edge.

Detailed Edge Metal Comparison Matrix: Eaves vs. Rakes

5. High-Wind Edge Details: FORTIFIED Drip Edge & Low-Slope Edge Securement (ANSI/SPRI ES-1)

In hurricanes, roof coverings often fail by peeling from the edge. Wind that hits a wall is deflected up over the eave and rake, creating strong suction on the edge metal and the first courses of the roof, and outward pressure on the face of the metal.

                                  WIND VORTEX FORCES ON EDGE METAL

                  Intense Negative Pressure (Uplift Suction)
                               ▲    ▲    ▲    ▲
                             ┌───────────────────────┐ <── Shingle Starter Course
     Accelerated             │ ===================== │ <── Edge Metal Deck Flange
     Wind Stream             └───────────┬───────────┘ <── Fasteners (code: 12" o.c. max)
          ▲                              │
          │             Horizontal Deck  │
          │                              ▼
     ─────┴─────┐           ┌────────────────────────┐
                │           │ Fascia Board           │
                │           │                        │
                │ <──── Prying Force Pushes Inward   │
                │      and Outward on Vertical Face  │
                │                                    │

Code Minimum vs. FORTIFIED Roof (Detail F-DE-1)

The Louisiana amendments approved in 2026 for the 2024 IRC (effective January 1, 2027) add an exception to R905.2.8.5: on a roof built to IBHS FORTIFIED standards, the FORTIFIED drip-edge requirements govern.

Good Practice at Corners and Laps

• Laps: On rakes, lap the upper piece over the lower piece so water runs over the joint, not into it. Nail through both layers near each lap.
• Corners: At eave-to-rake corners, install the eave piece first, running it slightly past the corner. Notch and fold it around the gable end. Then lap the rake piece over it so water running down the rake lands on top of the eave metal.
• Nails: Ring-shank nails hold better than smooth shanks. Use a metal compatible with the drip edge.

Low-Slope Roofs: ANSI/SPRI ES-1 (IBC 1504.6)

ANSI/SPRI/FM 4435/ES-1 is the test standard for edge systems on low-slope roofs (2:12 or less). IBC 1504.6 requires metal edge systems (except gutters and counterflashing) on built-up, modified bitumen, and single-ply roofs with slopes below 2:12 to be designed for Chapter 16 wind loads and tested with ES-1 methods:

• RE-1: tests the roof-edge termination of ballasted or mechanically attached membranes, where the membrane is not adhered or fastened within 12 inches of the edge.
• RE-2: a pull-off test for edge flashings (fascia-type metal whose exposed horizontal part is 4 inches or less), pulling outward on the vertical face.
• RE-3: a pull-off test for copings (exposed horizontal part more than 4 inches), pulling up and out at the same time.

Gutters used to secure a low-slope membrane edge must instead be tested to SPRI GT-1 (IBC 1504.6.1). ES-1 does not govern ordinary drip edge on steep-slope shingle roofs, which follows IBC 1507.2.8.3 or IRC R905.2.8.5.