What does drip edge do, and why does the lap order matter?
Drip edge is bent metal at the edge of the roof that forces water to let go and fall, instead of curling back underneath and running onto the fascia. It is required at both the eaves and the rakes of a shingle roof, and the underlayment order is deliberately opposite at each: at the eave the drip edge goes on the deck first and the underlayment laps over it, so the ice barrier can bond down over the metal and seal its fasteners; at the rake the underlayment goes down first and the drip edge is fitted over it, so water running on top of the underlayment exits over the metal rather than behind it. Segments should lap not less than two inches, fasteners run along the deck leg rather than the face, and the metal should be new. Reusing the old drip edge is the tell, because it is the same age as the shingles being torn off and reusing it makes the correct order impossible to build.
The one force it exists to defeat
Water does not simply fall off an edge. Run a tap slowly over the lip of a glass and watch the stream bend back under the rim and travel along the underside — that is surface tension holding the drop to the solid it is touching. A roof edge does the same thing, all winter, in slow motion.
The consequence is specific and expensive. Water leaving the bottom course of shingles curls around the edge of the sheathing and runs back, onto the top of the fascia board and down its face behind the gutter. Fascia is usually painted pine or a composite trim, and it is being wetted from the side nobody looks at and nothing can dry. The paint stays perfect while the wood behind it goes. By the time the fascia looks bad it has been wet for years.
Drip edge is one bend of metal that turns a clinging film of water back into a falling drop.
That is what the profile does. The lower leg of a drip edge kicks out, away from the fascia, and terminates in an edge — often a folded hem — that water cannot travel around. The drop reaches the end, has nothing to cling to, and falls. Every other job drip edge does is secondary to that one.
The secondary jobs are still worth having. It stiffens and protects the raw cut edge of the sheathing, which is the most absorbent surface on the whole roof. It gives the starter course a straight, supported line to sit on. It keeps wind from getting under the first course at the most exposed point on the roof. And at the rake it stops water travelling sideways off the underlayment into the edge of the deck.
The lap order is opposite at the eave and the rake, on purpose
This is the detail that separates a roof built to the requirement from a roof built by habit, and it is the one thing on this page worth memorising: underlayment over the drip edge at the eaves; underlayment under the drip edge at the rakes.
At the eave: metal first, then underlayment
The drip edge is fastened to the deck, and the ice-and-water membrane is then bonded down over the top of it. Two things happen as a result. The membrane seals every fastener holding the metal, and the bottom edge of the assembly becomes continuous — so under an ice dam, water standing on the membrane has nowhere to get behind the metal.
Fails when: Drip edge fitted last, on top of the membrane. The fasteners are then exposed to standing water at the exact location standing water occurs, and there is a lap facing uphill at the eave.At the rake: underlayment first, then metal
The rake is the sloped gable edge, and water there runs down the slope on top of the underlayment. The metal must sit over that surface so the water crosses onto it and off. Nothing is standing at a rake, so nothing needs to be bonded over the metal.
Fails when: Drip edge tucked under the underlayment at the rake, which routes water off the underlayment straight into the edge of the deck and down the rake board — a detail that rots a gable trim from the inside.The corner where they meet
Eave metal runs first and continues past the corner; rake metal starts at the bottom and laps over the top of it, so the higher piece always shingles over the lower one. On good work the corner is cut and folded rather than butted, so there is no open joint at the most exposed point of the roof.
Fails when: Two square ends butted together at the corner with a bead of sealant across the gap. The sealant fails first and the corner is the last place anyone looks.The laps between segments
Segments lap in the direction of flow — the upper piece over the lower — by not less than two inches. On a long eave that is a dozen laps, and each one is either right or a small funnel.
Fails when: Butted ends, or upper segments tucked behind lower ones, which turns each joint into an entry point.Why reuse is the tell. A quote that says "reuse existing drip edge" is not only reusing metal the same age as the shingles being torn off, at the most weather-exposed line on the building. It has also made the eave order impossible: the new membrane cannot bond over metal that is already buried under the old assembly, so the fasteners stay unsealed and the continuity at the edge is gone. The saving is a few dollars a linear foot. The cost is the one detail the eave depends on.
Profiles, and the one most roofs should have
Edge metal is sold in a handful of profiles, and the names get used loosely. What matters is the geometry: how far the metal reaches out past the sheathing, whether it kicks away from the fascia, and whether it lands inside the gutter or above it.
| What it looks like | Where it belongs | What it gets wrong | |
|---|---|---|---|
| Plain L drip edge | A simple right angle: one leg on the deck, one down the face. | Rakes, and eaves without gutters. | The vertical leg is short and sits close to the fascia. On a gutter run the water can bridge the gap and get behind the gutter. |
| Extended-face drip edge | An L with a longer face leg and a kick-out at the bottom. | The general-purpose eave and rake profile. This is the default on decent work. | Nothing much, provided the face leg is long enough for the fascia depth and the kick actually clears it. |
| Gutter apron | A wider profile with a long lower leg bent to reach out and down into the gutter trough. | Any eave with a gutter, and the single best retrofit on a house with fascia staining. | Frequently not quoted at all, because plain drip edge is cheaper and looks the same from the ground. |
| Rake edge | Same family, run up the gable. Often a slightly different profile so it sits over the underlayment cleanly. | Every rake. It is not optional and it is the piece most often skipped. | Omitted entirely on re-roofs, or the eave profile is used and the corner never closes properly. |
Drip edge and gutters are one detail, not two
A gutter hangs on the fascia, below and slightly outboard of the roof edge. There is a gap between the back of the gutter and the fascia, and if the metal above does not reach past that gap, water crossing it lands behind the gutter rather than in it — which is the same fascia-wetting failure as having no drip edge at all, just moved an inch. A gutter apron closes it by reaching over the back of the trough. If you have dark streaking on the fascia under a gutter, or peeling paint on the soffit at the eave, this is the first thing to look at, and it can be fitted without touching the roof.
The material details that are worth a sentence each
- Gauge and hem. Thin unhemmed aluminium waves visibly along a long eave and dents when a ladder touches it. A folded hem at the bottom edge stiffens the whole strip and removes the raw cut edge, which is where corrosion and paint failure start.
- Aluminium and treated lumber do not mix. Modern pressure-treated wood uses copper-based preservatives, and copper in contact with aluminium in the presence of water corrodes the aluminium. If edge metal is being fastened to treated fascia or treated framing, it needs to be isolated or a compatible metal used instead.
- Do not mix metals at the edge. Aluminium drip edge with copper gutters, or steel fasteners through aluminium, sets up a galvanic couple that eats the less noble metal. Fasteners should match the metal they are driven through.
- Fastener spacing. Along the deck leg, roughly every foot or closer, never through the face. A nail through the visible face of a drip edge is a hole in the water path with a nail head sitting in it.
- It must overhang the sheathing. The metal should project past the edge of the deck by a small but real amount, and turn back up onto the deck by a couple of inches. Metal set flush with the sheathing has nowhere to shed to.
How to check your own edge metal from the ground
Almost everything on this page is visible from a driveway with a phone camera. Nobody should be on a ladder to do it.
How to check the drip edge on your own roof from the ground
Do it once on each elevation. Photograph what you see, so you have a before-and-after if anything gets done later.
- Look for metal at the eave Stand back and look along the bottom edge of the roof, at the line where the shingles end. There should be a clean strip of metal visible below the shingle edge, running the full length. If the shingles simply end and you can see the edge of the plywood or the top of the fascia, there is no drip edge there.
- Look for metal up the rake Now look at the sloped gable edge, from the eave up to the peak. This is the piece most often missing entirely. The same clean metal line should run all the way up. Compare the two edges in your photos, because a house with eave metal and no rake metal is common and obvious once you know to look.
- Check where the metal lands relative to the gutter Look at the back of the gutter where it meets the fascia. Ideally the metal above reaches out over the back of the trough. If you can see a gap between the fascia and the gutter with nothing spanning it, water crossing that gap is running down behind the gutter.
- Read the fascia and soffit for evidence Dark vertical streaks on the fascia, peeling or blistered paint along its top edge, staining on the soffit boards at the eave, or a soft patch in the trim at a corner. Those are the symptoms of water getting behind the edge, and they appear years before anything shows up inside the house.
- Photograph every corner Go to each corner where an eave meets a rake and take a close photograph. Look for a folded, closed corner rather than two square ends with a gap or a smear of sealant across them. Corners are where edge details are finished quickly and they are the last place anyone inspects.
If that check turns up missing rake metal, no gutter apron, or streaked fascia, none of it is an emergency and none of it needs a whole roof. It does need to be on the scope in writing next time anyone works on that edge, which is the reason to have the photographs.
What we specify, and why
Edge metal is new, listed twice, and quoted by the linear foot
Drip edge is one of the least expensive line items on a roof replacement and one of the most consequential, which is precisely the combination that gets it left off a summary. It appears twice on our scopes because there are two edges.
- New drip edge at the eaves — never reused — set on the deck before the membrane
- New drip edge at the rakes, listed separately, fitted over the underlayment
- Linear feet stated for each, so the quantity can be checked against the roof
- Gutter apron where there is a gutter, so the metal reaches into the trough
- Laps of at least two inches, upper over lower, in the direction of flow
- Fasteners in the deck leg at close spacing, never through the visible face
- Corners cut and folded rather than butted and sealed
- Compatible metals and fasteners, and isolation where metal meets treated lumber
How to tell whether a contractor is cutting this corner
The metal is the same age as the roof coming off, at the most weather-exposed line on the house, and reusing it makes the correct eave order impossible — the new membrane cannot bond over metal that is already buried.
Ask instead: for new drip edge at eaves and rakes, as two separate line items with linear feet.One line for two different edges with two different lap orders. It is also the phrasing used when only the eaves are priced, because the eaves are what a homeowner looks at.
Ask instead: how many linear feet at the eaves and how many at the rakes.Gutters and drip edge solve different halves of the same problem. A gutter catches water that has already left the roof; the metal is what makes it leave cleanly instead of curling back onto the fascia.
Ask instead: whether a gutter apron is included, since that is the profile that bridges the gap behind the gutter.Sealant is a finishing detail, never a substitute for geometry. At a corner it is being asked to bridge an open joint at the windiest, wettest point on the roof, and it has a service life of a few seasons.
Ask instead: for the corners to be cut and folded closed.Possibly fine. But gauge, hem and face length are the difference between a straight edge that lasts and a wavy one that dents, and aluminium against treated lumber is a corrosion detail, not a preference.
Ask instead: what gauge, whether the bottom edge is hemmed, and how long the face leg is relative to the fascia.It is required at both eaves and rakes on a shingle roof, and the rake is the piece most often absent on a re-roof because nobody looks up the gable.
Ask instead: to be shown the rake edge on a finished job before you sign.Drip edge questions DMV homeowners ask
Is drip edge actually required, or is it optional?
It is required at both the eaves and the rake edges of a shingle roof under the model residential code that Maryland and Virginia build from, along with rules for how it is lapped and fastened: segments lapping not less than two inches, mechanical fastening along the deck leg at close spacing, the metal extending past the edge of the sheathing and turning back up onto the deck. It is also one of the least expensive components on the roof. If a quote does not name it at both edges, that is worth a question before anything else on the page.
What is the difference between drip edge and gutter apron?
Geometry, not category. A gutter apron is a drip edge with a longer lower leg bent to reach out and down into the gutter trough, so water crossing from the roof lands inside the gutter instead of in the gap between the gutter and the fascia. Plain drip edge often stops short of that gap, and water bridging it runs down the back of the fascia where nothing can dry and nobody looks. On any eave with a gutter, the apron profile is the right one, and it is a very effective retrofit on a house that already shows fascia staining.
Should underlayment go over or under the drip edge?
Both, depending on which edge. At the eaves the drip edge is fastened to the deck first and the underlayment or ice barrier laps over the top of it, so the membrane seals the metal fasteners and the bottom of the assembly is continuous against water standing behind an ice dam. At the rakes the order reverses: underlayment first, drip edge over it, so water running down on top of the underlayment crosses onto the metal and off rather than draining behind it into the edge of the deck. Getting the rake backwards is a common and quiet mistake that rots gable trim from the inside.
Can drip edge be added without replacing the roof?
A gutter apron can, in most cases, because it slides up under the first course of shingles and over the back of the gutter without disturbing the field of the roof. Full drip edge at an eave is harder to retrofit properly, since the correct order puts the metal under the underlayment, and rake edge can usually be added with care. If your issue is water getting behind the gutter and staining the fascia, the apron is usually the right answer and it is a small job. If the edge metal is missing altogether on a roof that is already near the end of its life, it is a reason to plan the replacement rather than patch the edge.
Why is my fascia rotting when the roof looks fine?
Because the two failures are on opposite sides of the same edge. Water leaving the bottom course of shingles will curl back under the edge of the sheathing if nothing forces it to let go, and it then runs onto the top of the fascia and down the face behind the gutter. The paint on the outside stays intact while the wood behind it stays wet, so the roof looks perfect and the trim quietly fails. Missing drip edge, drip edge that does not reach past the back of the gutter, and reused metal at a re-roof are the three usual causes, and all three are visible from the ground.
Where to go next
The edge is one of the four places a roof plane stops. The others are the valley, the wall and the penetration — and each has its own metal.
Valleys: open, closed-cut and woven
One channel carrying the runoff of two roofs. Which construction belongs on which geometry, and where the fasteners must not be.
Read the standard →FlashingFlashing and penetrations
Step, kick-out, apron, counterflashing, crickets and boots — named, with what fails in each.
Read the standard →Ice barrierIce-and-water shield: where it must go
The membrane that bonds over your eave drip edge, and the 24-inch rule most quotes get wrong.
Read the standard →ServiceGutters and downspouts
The other half of the edge detail — sized, pitched and hung so the water the roof sheds actually leaves the building.
See the service →