Field guide

Drip Edge: The Two-Dollar Detail That Decides Whether Your Fascia Rots

Drip edge is a formed metal flashing at the eaves and rakes that breaks the path water takes as it clings to the underside of the shingle edge. Without it, water wicks back onto the fascia and rots it from the outside in. IRC Section R905.2.8.5 has required it on asphalt shingle roofs since the 2012 code cycle.

Water does not fall off a roof. It clings

The physics is unglamorous and it is the whole story. Water running off a shingle edge does not just drop. It clings to the underside through surface tension and travels back toward the building before it falls, wetting the top of the fascia and the cut edge of the deck. A drip edge is a narrow strip of formed metal, usually aluminum or galvanized steel, bent roughly into an L and nailed along the edges of the roof deck. Its downturned leg holds the water away from the wood and gives it a clean line to fall from, into the gutter.

Without it, the damage is slow and mostly invisible. Water repeatedly wicks behind the shingle edge and saturates the wooden fascia board. In a hot, humid climate that wood starts to rot within a few years, and replacing fascia on a full roofline typically runs $1,500 to $3,000. The metal that would have prevented it runs roughly $1 to $2 per linear foot. Drip edge costs less than one percent of most roof budgets, and it is still the single most common reason roofers find rotted fascia, water-stained soffits, and premature deck failure.

What the code actually requires

Metal drip edge became a requirement in the 2012 edition of the International Residential Code. Section R905.2.8.5 requires drip edge at the eaves and rake edges of shingle roofs, with five specifics: adjacent segments must overlap at least two inches, the vertical leg must extend at least a quarter inch below the sheathing, the flange must extend at least two inches back onto the roof deck, fasteners go at no more than twelve inches on center, and the underlayment goes over the drip edge at the eaves and under it at the rakes.

That last detail is the one crews get backwards. At the eave, the drip edge goes down first, directly on the deck, and the underlayment laps over it, so water running down the underlayment flows onto the metal and off the roof. At the rake the order flips: underlayment first, drip edge on top. Put the underlayment under the drip edge at the eave and water on the underlayment runs off its edge behind the metal, straight onto the fascia. The roof looks perfect and the fascia rots anyway. The code sets no metal gauge or profile, so Type C, Type D, and Type F gutter apron are all acceptable; the layering order is what matters.

The warning signs on an older roof

The first sign is rarely a ceiling stain. It is peeling paint or soft wood along the fascia, or water stains on the siding below the roof edge, behind the gutter. Gutters do not substitute for drip edge: they catch the water, but drip edge is what keeps it from running behind the gutter onto the fascia, and the code requirement applies either way on a shingle roof. Homes built before 2012 often have no drip edge at all, which is why a reroof on an older house is the moment the deficiency gets found.

If a contractor skips drip edge to save a few hundred dollars on your project, they are not just cutting a corner, they are violating code, and a building inspector can flag it during the roof replacement permit inspection. The work may not pass until it is added. When you get the quote, check that drip edge is a line item at both eaves and rakes, and check the crew's layering order at the eave before the underlayment goes down. After the shingles are on, the order is uncheckable.

A two-dollar part with a three-thousand-dollar failure mode

Roofing has plenty of expensive components, and this is not one of them. The cost of drip edge is trivial next to the cost of the fascia, soffit, and deck edge it protects, and the code has required it for fourteen years. If your roof has no drip edge, the fix is a reroof item, not a repair, because the metal has to go under the first course of shingles. That is the real reason to check for it now rather than at the next replacement: the next replacement is when it gets fixed, and the fascia is rotting in the meantime.

Frequently asked questions

Is drip edge required by code?

Yes, on asphalt shingle roofs. The International Residential Code has required it since the 2012 edition, in Section R905.2.8.5. It must be installed at eaves and rakes, with the underlayment over it at the eaves and under it at the rakes.

How much does drip edge cost?

Standard aluminum drip edge runs roughly $1 to $2 per linear foot for materials, less than one percent of most roof budgets. Skipping it to save a few hundred dollars can lead to fascia replacement costing $1,500 to $3,000.

Can gutters replace drip edge?

No. Gutters catch water, but drip edge is what keeps water from running behind the gutter onto the fascia. The code requirement applies whether or not the house has gutters.

What happens if drip edge is installed backwards?

Water gets trapped behind the metal and causes the damage the flashing was supposed to prevent. At the eave, underlayment must lap over the drip edge; at the rake, the drip edge goes over the underlayment. Installed the wrong way round, the roof looks fine while the fascia rots.