What is the difference between a gutter apron and drip edge?
The profiles
- L-style (sometimes called C-style). A simple right angle: one leg on the roof deck, one down the face of the fascia.
- T-style or D-style. Adds a small outward kick at the bottom that throws drips clear of the fascia. Common on Georgia replacements.
- Gutter apron. The roof leg is similar, but the lower leg is longer and bent so it hangs down inside the back of the gutter. It is used only at eaves, typically where the gutter sits low or a gap has opened between gutter and fascia.
What the code requires
The International Residential Code requires drip edge at the eaves and rake edges of asphalt shingle roofs. It calls for pieces to overlap at least 2 inches, extend at least a quarter inch below the sheathing, run at least 2 inches back onto the deck, and be fastened at no more than 12 inches on center. At the eaves the underlayment laps over the metal, and at the rakes the metal goes over the underlayment, so water always flows onto the next layer down instead of under it.
Why it matters for your gutters
Water clings to surfaces. Without metal bridging the roof edge to the gutter, a thin stream rolls back under the shingles, down the fascia and behind the gutter. Over a few years that rots the fascia and the ends of the rafters and stains the soffit. Shingles should also overhang the metal slightly, commonly a quarter to three quarters of an inch, so water drips cleanly into the trough.
Gutter apron can be slipped in on an existing roof by lifting the first course carefully, but the cleanest time is a full replacement. More on the details in drip edge explained and roof flashing explained.