Standard Roofing Practices for the Edge of a Roof

Galvanized Steel or Aluminum

• Drip edge flashing should be installed along both eaves, where the roof goes over the wall, and the rake, the slope side of a gable roof. Every exposed shingle edge should be covered. Most drip edge is aluminum or galvanized steel shaped at a 90-degree angle with one flat side and one side that has a lip at the edge to direct water away from the house. The most common type is 1 1/2 inches on both sides, but widths and styles vary.

Drip Edge During Roofing

• Install the drip edge after the roof is decked with plywood or oriented strand board (OSB) but before any roofing paper or moisture underlayment is put down. Start at one end of an eave, and set the drip edge in roofing cement, placing it tight against the roof decking and the fascia or facing board. See that the end of the drip edge is flush with the side trim or rake board. Nail both ends of the edge first to hold it firmly, and add nails in between about 18 inches apart.

Overlap Edging Sections

• Put down roofing paper only after the bottom drip edge is installed, and add drip edge along the rake or gable sides on top of the paper to insure that any water that gets in under the shingles goes down the drip edge on the side and over the drip edge on the bottom. Overlap drip edge pieces at least 2 inches from top to bottom and away from any prevailing winds on the eaves.

Add Drip Edge to the Existing Roof

• You can add drip edge on an existing roof by lifting the bottoms of the shingles enough to slide the metal flashing underneath the shingles. Secure this drip edging with roofing cement on both sides of the metal, rather than nails. Press the shingles down firmly onto the cement, and hold them a few seconds until the cement bonds. If you can lift the shingles high enough, add nails at the ends, but don't break the shingles.

Nail the Overlaps

• Overlap edging at the corners with the rake edge overlapping the eave edge. Cut the edging with tin snips to remove the bottom portion so the edging corner is flush. At gable peaks, cut a V from the lower half of a section of edging, and bend the top piece over the peak so the V sides overlap. Cut and form this peak section, and finish installing down the sides, but ensure overlaps are from the top. On overlaps, nail through both pieces of edging. An alternative at the peak is to run one strip clear to the peak; then cut out a piece of the bottom of an adjoining section, and fold the top piece over the peak.