Where does drip edge go, and how is it placed?
Short answer. Drip edge goes along every eave and every rake of the roof. At the eaves it is installed directly on the deck under the underlayment, and along the rakes it goes on top of the underlayment, so water at each edge always runs over the metal and away from the wood.
At the eaves
- The roof flange lies flat on the bare deck, and the face hangs down snug over the fascia.
- Underlayment, and any self-adhered leak barrier at the eave, laps over the top of the flange.
- With gutters, the drip edge or a gutter apron should reach over the back edge of the gutter so water drops into the trough instead of behind it.
- The starter strip and first course then overhang the metal slightly, commonly 1/4 to 3/4 inch per the manufacturer.
Along the rakes
- Underlayment goes on first, running to the edge of the deck.
- The rake drip edge goes over it, so wind-blown rain that gets under the metal lands on the underlayment.
- Shingles overhang the rake metal by a small, even amount.
Fastening and laps
Nails go high on the roof flange, where shingles will cover them, no more than 12 inches apart. Joints overlap at least 2 inches, with the upper or downstream piece lapped correctly so water runs over the seam. At outside corners, the rake piece laps over the eave piece.
Where drip edge does not go
Hips, ridges and valleys are interior lines covered by caps and valley linings. Where a roof meets a wall, step flashing and headwall flashing do the job instead. Low-slope porch roofs with membrane roofing use their own edge metal.
A common placement mistake
Setting eave drip edge on top of the underlayment lets water running down the sheet slip behind the metal and onto the fascia, the very thing drip edge is meant to prevent.