11.1 Drip Edge & Roof-Edge Metals (R905.2.8.5 and R903.2)

Why Edges Need Metal

Water running off a roof edge clings to the edge and can wick back behind the shingles, soaking the sheathing edge and fascia. Wind also drives rain under rake edges. A drip edge supports the shingle overhang, directs water clear of the fascia, and protects the deck edge. In Michigan, the eave detail must also work with the ice barrier (Section 8.3).

The Code Rule (R905.2.8.5)

A drip edge shall be provided at eaves and rake edges of shingle roofs. Adjacent segments of drip edge shall be overlapped not less than 2 inches. Drip edges shall extend not less than 1/4 inch below the roof sheathing and extend up back onto the roof deck not less than 2 inches. Drip edges shall be mechanically fastened to the roof deck at not more than 12 inches o.c. with fasteners as specified in Section R905.2.5. Underlayment shall be installed over the drip edge along eaves and under the drip edge along rake edges.

General Flashing Rules (R903.2)

• R903.2: flashings must keep moisture out of walls and roofs through joints in copings, through moisture-permeable materials, and at intersections with parapet walls and other penetrations.
• R903.2.1 locations: flashing is required at wall and roof intersections, wherever there is a change in roof slope or direction, and around roof openings. It also requires a flashing that diverts water away where the eave of a sloped roof meets a vertical sidewall, which is the kick-out (Section 11.2).
• Metal thickness: where flashing is metal, it must be corrosion-resistant and at least 0.019 inch (No. 26 galvanized sheet).
• R903.3: parapet walls need noncombustible, weatherproof coping at least as wide as the wall.

The code sets drip edge dimensions and fastening but does not give a separate drip edge gauge table. Choose a durable, corrosion-resistant product, such as galvanized, prefinished steel, aluminum, or copper, compatible with the gutters and other metals. Use the shingle manufacturer's accepted profiles where a system warranty is involved.

Common Profiles

Installing Drip Edge

At the Eave

1. Install the drip edge directly on the deck along the eave. Set the face tight to the fascia, and extend it at least 1/4 inch below the sheathing.
2. Nail through the deck flange at no more than 12 inches on center, into the deck. Don't nail through the face into the fascia, because face-nailing can buckle the metal as it moves with temperature.
3. Lap pieces at least 2 inches. Many installers lap in the direction that sheds water away from prevailing winds.
4. Apply the ice barrier and underlayment over the drip edge flange (R905.2.8.5).

At the Rake

1. Install the underlayment first, running it to the rake edge.
2. Install the rake drip edge over the underlayment, and nail at no more than 12 inches on center.
3. At the bottom of the rake, lap the rake piece over the eave piece so water running down the rake flows onto the eave metal, not behind it.
4. At the top of a gable, lap the lower piece under the upper piece so water sheds downslope, or miter it neatly per the manufacturer.

Shingle Overhang

Shingles overhang the drip edge slightly, commonly about 1/4 to 3/4 inch, as the manufacturer specifies. The starter course's sealant near the edge keeps the first course from lifting.

Gutters and Drip Edge

• The drip edge or gutter apron should shed water into the gutter, not behind it. Set gutters so the drip edge extends past the gutter's back edge.
• In Michigan, ice and snow load gutters heavily. Use strong hangers at close spacing, per the gutter manufacturer. Keep downspouts discharging away from foundations.
• Gutters are a separate M&A trade (siding and gutters). A roofer may do incidental gutter work related to the roof, such as removing and reinstalling gutters (MCL 339.2404(3)).

Material Compatibility

• Don't mix copper with galvanized steel or aluminum where runoff or contact causes galvanic corrosion. Copper runoff also stains and corrodes aluminum gutters.
• Use fasteners of a compatible metal: galvanized with galvanized, stainless or copper with copper. The code requires compatible materials (R904.2).
• Prime metal before adhering bituminous products where required (R908.6 for reroofing flashings).

Reroofing

On a reroof, replace rusted, damaged, or deteriorated edgings and flashings (R908.5). Installing new drip edge on a tear-off lets you set the ice barrier over the flange properly. On a legal recover, the new roof must still meet Chapter 9, including drip edge (R908.1).