What Drip Edge Does
Drip edge is a thin metal flashing — typically aluminum or galvanized steel — installed along the eaves (lower edges) and rakes (side edges) of a roof. Its functions:
- Directs water off the roof edge and into the gutters rather than letting it run down the fascia board
- Prevents water from wicking back under the first course of shingles by capillary action
- Protects the exposed deck edge from water infiltration
- Provides a clean finished appearance at the roof edge
- Creates a defined edge that keeps shingles from overhanging too far
What Happens Without Drip Edge
Roofs without drip edge suffer predictable problems over time:
- Fascia rot: Water running down the face of the shingles hits the fascia board directly. Over years, this causes wood rot that eventually requires fascia replacement.
- Deck edge deterioration: The exposed OSB or plywood deck edge wicks moisture and delaminates, creating weak spots at the roof perimeter.
- Shingle back-wicking: In heavy rain, water can travel back up under the starter course of shingles — the same mechanism that ice dams exploit in winter.
- Gutter issues: Water running behind gutters instead of into them can damage soffit and fascia, and direct water to the foundation.
Correct Drip Edge Installation
At the eaves (bottom edges), drip edge is installed UNDER the underlayment. At the rakes (side edges), drip edge is installed OVER the underlayment. This sequence matters:
- Eave drip edge under underlayment allows water that gets under the underlayment to drain out over the drip edge
- Rake drip edge over underlayment directs water off the side edge before it can get under the underlayment
- Reversed installation — rake drip edge under underlayment — is a common installation error that allows water entry
Drip Edge Materials and Styles
- Aluminum: Most common. Lightweight, rust-resistant, paintable. Available in many colors to match the roof or fascia.
- Galvanized steel: Stronger than aluminum, used in high-wind areas. May rust at cut edges over time.
- Type C (standard): L-shaped, basic drip edge. Most commonly used.
- Type D (T-style): Has a longer leg with a drip groove that extends further away from the fascia. Better water management in heavy rain areas.
Frequently Asked Questions
What does drip edge do on a roof?
Directs water off the roof edge and into gutters, prevents water from wicking back under shingles, and protects the deck edge and fascia from water infiltration.
How do I know if my roof is missing drip edge?
Look at the roof edge meeting the gutters. If you see bare wood fascia, shingles with no metal beneath them at the edge, or signs of fascia rot, drip edge may be missing or incorrectly installed.
Can drip edge be added without replacing the whole roof?
Yes. A contractor can install drip edge on an existing roof by lifting the first course of shingles, sliding drip edge underneath, and re-securing the shingles. More labor-intensive but worthwhile for active damage.
Get a Roof Edge Inspection
This page is for general informational purposes only. Building code requirements for drip edge vary by jurisdiction. Consult a licensed roofing contractor for an assessment of your specific roof installation.