What Is Drip Edge, and Is It Required on a Shingle Roof?

Drip edge is a strip of formed metal, bent roughly into an L, nailed along the edges of the roof deck. One leg lies flat on the deck. The other hangs down past the edge of the deck and over the top of the fascia board, often with a small kick at the bottom.

It does three jobs. It terminates the roof edge cleanly, so the shingles and underlayment end on metal instead of a raw wood edge. It sheds water off the roof and away from the fascia. And it gives the first course of shingles a straight, stiff line to overhang.⁴

The physics behind the "drip" is surface tension. Water running off a shingle edge doesn't just fall. It clings to the underside and can travel back toward the building before it drops, wetting the top of the fascia and the cut edge of the deck. A drip edge's downturned leg holds the water away from the wood and gives it a clean line to fall from.

Yes, on asphalt shingle roofs. Metal drip edge became a requirement in the 2012 edition of the International Residential Code.³ Section R905.2.8.5 requires:¹²³

• Drip edge at the eaves and rake edges of shingle roofs.
• Adjacent pieces overlapped at least 2 inches.
• A vertical leg that extends at least 1/4 inch below the roof sheathing.
• A flange that extends at least 2 inches back onto the roof deck.
• Mechanical fastening to the deck at no more than 12 inches on center, using roofing nails of the kind the code specifies for shingles.
• Underlayment installed over the drip edge along the eaves and under it along the rakes.

The code's drip edge section is written for asphalt shingles. NRCA notes the IRC has no specific drip edge requirement for clay and concrete tile, metal shingles, slate, or wood shakes and shingles, and recommends considering one on those systems based on climate and edge framing.⁴

Stronger programs go further. The IBHS FORTIFIED high wind and hail re-roofing checklist calls for drip edge that extends 1/2 inch below the sheathing and at least 2 inches back on the roof, overlaps 3 inches at joints and is fastened at 12 inches on center, staggered.⁵

This is the detail most often done backwards, and it is worth understanding rather than memorizing.

At the eaves, water flows downhill across the underlayment toward the edge. NRCA describes the drip edge being applied directly to the deck with its flange covered by the underlayment.⁴ Any water on the underlayment then runs onto the top of the metal and off the drip leg. Put the underlayment under the drip edge here and water on the underlayment runs off its edge behind the metal, straight onto the fascia.

At the rakes, water isn't flowing toward the edge. The risk is wind-driven rain pushing sideways under the edge. So the underlayment goes on first and the drip edge laps over it, sealing the edge of the underlayment under metal. NRCA adds that rake pieces should start at the eave and run up the slope, so each piece laps over the one below and sheds water shingle fashion.⁴

Where a self-adhering ice barrier membrane is used at the eaves, NRCA notes the drip edge can go over the membrane and be stripped in with a 6- to 10-inch strip.⁴ Owens Corning's instructions likewise call for underlayment over the drip edge at the eave and under it at the rakes, or as local code requires.⁶

The drip edge sets the line; the shingles finish it. Owens Corning's instructions call for starter shingles to overhang the drip edge along the rakes and eaves by 1/4 to 3/4 inch, and allow shingles to be flush with D, F or T-style drip edge.⁶ NRCA gives the same range for L-type drip edge, and flush to about 3/4 inch for T-type.⁴

Too little overhang and water runs down the face of the metal. Too much and the unsupported shingle edge can sag in summer heat and gives wind more edge to grab.

• Missing entirely. Possible on older roofs, since the code only began requiring drip edge in 2012.³ Water wicks back to the fascia and the deck edge, which rot slowly from the outside in. The first sign is often peeling paint or soft wood along the fascia, not a ceiling stain.
• Underlayment on the wrong side at the eave. Water that reaches the underlayment drains behind the metal. The roof looks perfect and the fascia rots anyway.
• Reverse laps on the rake. Pieces installed from the top down, so each lap points uphill and catches water instead of shedding it.
• Short laps or gaps between pieces. Each joint under 2 inches is a place water can get behind the metal.¹
• Under-fastening. Nails spaced too far apart let the edge flex and lift. Roof edges, eaves, hips and ridges are where wind damage tends to concentrate,⁷ so a loose edge is the start of a bigger failure. See wind damage to shingles.
• Wrong overhang. Shingles cut flush with an L-style edge, or hanging well past it.
• Gutter conflicts. At the eave, drip edge and gutters have to work together so runoff lands in the gutter and not behind it. See our gutter page.

A reroof is the right time to add or replace drip edge, because the underlayment has to lap with it correctly at the eave. Some cities make that explicit. Fort Worth's roofing FAQ says drip edges are required during re-roofing even if none existed before.⁸ Universal City's re-roofing bulletin states that drip edge is required on all asphalt shingle roofing projects and that seams must overlap properly.⁹

On a full roof replacement, old drip edge should come off with the old roof and new metal should go on in the right lap order. Reusing bent or rusted edge metal saves little and locks in the old detail. On an overlay, the edge is usually built up instead of rebuilt, one of several reasons we don't recommend roofing over old shingles.

Fixing drip edge alone, without a reroof, is possible but fussy, because the first courses of shingles and the underlayment have to be lifted to lap the metal correctly at the eave. It is quoted as a roof repair; Atrium's repair minimum is $250.

Central Texas spring storms bring heavy rain and strong gusts together. That is the worst case for a rake edge with the wrong lap, because wind pushes water sideways under the edge exactly where the drip edge is supposed to seal it. It is also the worst case for a loosely fastened edge.

Requirements also vary across the metro. Universal City requires drip edge on all asphalt shingle projects.⁹ If you live in Universal City or another city with its own bulletin, a quote that leaves drip edge out isn't just missing a line item. It is missing a requirement.

Drip edge is an inexpensive component and an expensive one to omit, because the damage it prevents is fascia and deck rot. Because the code requires it on shingle roofs, a shingle replacement quote should list it. When you compare quotes, check that drip edge is included at both eaves and rakes. Our roof cost guide lists the other line items worth comparing.