What Is a Drip Edge?

Drip edge is usually aluminum or galvanized steel bent into an L or T profile, with a short flange that lies flat on the deck and a lip that projects just past the edge. Water runs off the lip and falls free instead of tracking along the underside of the shingle to the wood. Layering order matters. At the eaves, the underlayment is laid over the metal, so water that gets under the shingles runs down the underlayment and out over the lip. At the rakes, the metal goes over the underlayment, so wind-driven rain cannot be pushed beneath it.

On an estimate, drip edge is priced by the linear foot, so aerial measurement reports list eave and rake lengths separately. On an insurance claim it is a regular source of friction. Plenty of older roofs went on without it, and an adjuster may leave it out of the scope because the original roof had none. Contractors respond that the model residential code has called for it for over a decade and that a new roof has to meet the code where the house stands. Whether the carrier pays turns on the policy’s code-upgrade wording and on local adoption.

Two mistakes come up again and again. One is reversing the layers, with metal over the underlayment at the eave, which hands water a path in behind it. The other is accepting a substitute. A bead of caulk, or a shingle that simply overhangs the edge, does not do the same job, and bare overhanging shingles droop and wick moisture into the edge of the deck.