What flashing goes on the gable end of a roof?
The rake edge: drip edge or gable trim
The IRC requires drip edge at both the eaves and the rakes of an asphalt shingle roof. At the rake the layering is reversed from the eave: the underlayment goes down first and the drip edge goes on top of it, so water running along the edge lands on metal instead of bare decking. The metal should reach at least 2 inches back onto the deck, hang at least a quarter inch below the sheathing, overlap the next piece by 2 inches, and be nailed no more than 12 inches apart. Shingles then overhang the metal slightly, usually a quarter to three quarters of an inch under most manufacturers' instructions.
On a metal roof, the same edge gets a rake trim that wraps over the panel edge and down the fascia, fastened and sealed to the panel maker's details.
Where a roof meets a gable wall
A porch or garage roof that butts into the side of a taller gable needs sidewall flashing: individual step flashing pieces at least 4 inches up the wall and 4 inches onto the roof, one per shingle course, with the siding lapped over the vertical legs. At the bottom, a kickout flashing turns the water into the gutter instead of letting it run down the wall. A missing kickout is one of the most common reasons for rotted sheathing and stained drywall below a roof to wall corner.
Why gable edges fail in Georgia
- Rakes and corners take some of the strongest wind uplift on a roof, so thunderstorm gusts peel shingles there first.
- Without drip edge, water wicks into the fascia and rake board, which shows up as peeling paint and soft wood.
- Rake shingles cut flush expose wood, while shingles that hang too far past the edge flap and tear in wind.
For the details, see drip edge explained and roof flashing explained.