What is drip edge metal, and does a metal roof need it?
What it is made of
- Aluminum: light, rustproof, sold prepainted in many colors.
- Galvanized or painted steel: stiffer and more dent resistant.
- Copper: for high-end or historic work.
It comes in 10-foot pieces in profiles such as L-style, D-style with a kick-out, and gutter apron.
How it works on a shingle roof
At the eaves, drip edge goes on the deck first and the underlayment laps over it, so water running down the underlayment lands on the metal and drips into the gutter. At the rakes, underlayment goes first and the drip edge over it. The code requires a flange at least 2 inches onto the deck, a lip at least 1/4 inch below the sheathing, and fasteners no more than 12 inches apart.
How metal roofs handle it
Metal roofs use an eave trim, sometimes simply called drip edge, that the panels sit on or hook over, and a rake or gable trim that covers the panel edge. Some manufacturers install a separate drip edge under the eave trim, while others combine the two. The sequence with underlayment varies, so the panel maker's installation details govern.
Matching metals
Keep dissimilar metals apart: aluminum against copper, or steel panels draining onto copper, can corrode. Use compatible fasteners too.
Why it matters
Without a proper edge, water wicks back onto the fascia and deck edge, causing rot that is often discovered only at tear-off. See drip edge explained and metal roofing in Georgia.