How to Install Drip Edge: Eaves Under the Membrane, Rakes Over the Underlayment
A strip of bent metal along the roof edge that sends water into the gutter and off the wood. The order of layers is the whole trick.
- Intermediate
- 2 to 4 hours for a typical house
- Updated
The short answer
Install drip edge by fastening it directly to the bare deck at the eaves, then laying ice and water shield and underlayment over its top flange. At the rakes, put the underlayment down first and fasten the drip edge over it. Lap joints about 2 inches, nail along the top flange about every 12 inches, and cut mitres at corners so water is directed into the gutter and away from the fascia.
Drip edge is a thin metal flashing bent to fit over the edge of the roof deck and down over the top of the fascia. Its job is simple: to direct water away from the wood. Without it, water can curl under the edge of the shingles and run behind the gutter and down the fascia, where it rots the board and the ends of the rafters. With it, water drops clear of the wood into the gutter.
It also stiffens the first row of shingles and protects the deck edge, and most shingle manufacturers call for it. The critical point is the order of the layers. At the eaves the drip edge goes under the underlayment and membrane, so water that gets through the roof runs onto the metal. At the rakes it goes over the underlayment, so wind-driven rain cannot be blown under the metal. Get this backwards and you build a slot that pulls water in.
This guide covers the installation. The membrane that goes with it is in how to install ice and water shield, and the wider edge detail is in how to install gutter apron. Metal panel roofs use a matching eave trim instead, see how to install metal eave trim.
Tools
- Tin snips (straight cut and offset)
- Hammer or coil nailer
- Chalk line
- Tape measure
- Hand seamer
- Utility knife
- Speed square
- Cut-resistant gloves
Materials
- Drip edge in 10 foot lengths, aluminum or galvanized steel, sized for the fascia
- Corrosion-resistant roofing nails, 1 inch to 1-1/4 inch
- Ice and water shield and underlayment
- Sealant compatible with metal for corner joints
- Touch-up paint for cut ends on coloured metal
Safety first
- Stay tied off. Edge work puts you near the eave, where a fall is most likely.
- Cut metal edges are razor sharp. Wear cut-resistant gloves and glasses when snipping.
- Never stand on a loose length of drip edge, which slides on the deck.
- Keep the ladder stable and tied off, and do not lean out past your belt buckle at the eaves.
Step by Step
Step 1: Check the fascia and the deck edge first
Press a screwdriver into the fascia top and the deck edge. Rotten wood does not hold nails, and metal over rot only hides the problem. Replace bad boards first using how to replace a rotten fascia board. Check that the deck edge is level with or slightly above the fascia top so water runs onto the flange, not into a gap.
Decide the type of drip edge. Standard T-style has a flange on the deck and a hemmed leg over the fascia, and an L-style is simpler. Match the depth of the leg to the fascia so it covers the top but does not hang low.
Step 2: Install the drip edge at the eaves first, directly on the deck
Start at one end and work across. Set the flange tight to the deck, snug to the fascia leg, and make sure the drip kicks out slightly so water falls clear, not onto the fascia. Some roofers leave about 1/4 inch of space. Nail along the upper part of the flange, near the top edge where the membrane will cover it, about every 12 inches. Some products call for closer spacing, so check the packaging.
Do not nail through the face on the fascia leg unless the manufacturer says to. Nail holes in the vertical face let water in and stain the metal.
Step 3: Lap the joints about 2 inches and stagger
At the eaves, water flows along the gutter and to the downspouts, but the main water flow is down the roof, so the lap direction is less critical than at the rake. Still, lap each joint by about 2 inches and nail through both layers near the top. Keep laps away from valley ends where water concentrates, and stagger them so they do not land at the same place as the gutter joints.
Some roofers overlap so the joint faces away from the prevailing wind. Check the BC Building Code and the shingle maker for the lap requirement.
Step 4: Install the membrane and underlayment over the eave drip edge
With the drip edge fixed to the deck, stick the eave membrane over the flange and onto the deck, and then lap the field underlayment over it. The layers lap downhill over the metal, so any water that gets through runs onto the metal and out. See how to install ice and water shield.
Step 5: Install the rake drip edge over the underlayment
At the rakes, the underlayment runs to the edge of the deck first. Then the drip edge goes over it, so that wind-driven rain pushed up the rake cannot slip under the metal and into the deck edge. Start at the eave and work up the rake so each piece laps over the one below, like a shingle. The lowest rake piece should lap over the eave drip edge.
Nail at about 12 inches in the top flange, and keep the nails at least 1/2 inch from the edge. Keep nail heads flat so they do not show through the shingles.
Step 6: Cut and fit the corners
At the eave-to-rake corner, cut the eave piece so it stops flush with the rake edge, and lap the rake piece over it. At inside corners, such as at a dormer, mitre the pieces or overlap them. Use a hand seamer to fold tabs and snips to cut relief notches. Seal the mitre joint with compatible sealant where the manufacturer permits, but rely on the lap rather than caulk.
Tip: Cut a few test corners on scrap first. Clean corners are what people see from the ground.
Step 7: Check the finished edge before shingles go on
From the ground, the metal should look straight and tight. On the roof, check that nail heads are flush, laps are in the correct direction, and the metal does not stand more than a hair off the deck. Shingles should overhang the drip edge by about 1/2 inch to 3/4 inch at the eaves, as the manufacturer specifies, so the water drips clear.
Eave or Rake: The Order of Layers
- Eaves: deck, then drip edge, then membrane and underlayment, then shingles. Water runs onto the metal.
- Rakes: deck, then underlayment, then drip edge, then shingles. Wind-driven rain cannot get under the metal.
- Rule of thumb: the layer upslope always laps over the layer downslope where water flows, and the metal goes over the underlayment where wind drives water uphill.
Fraser Valley Notes
Wind and rain off the valley floor blow up rake edges, and long wet winters test every gap at the eaves. Use corrosion-resistant metal and nails, and be careful with aluminum near fresh cedar or treated lumber, which can corrode it. Check the fascia for rot before covering it with new metal.
Common Mistakes
- Eave drip edge on top of the membrane. Water running down the membrane goes behind the metal and into the fascia.
- Rake drip edge under the underlayment. Wind-driven rain gets between the deck edge and the metal.
- Short laps. Under about 2 inches, joints let water through.
- Nailing through the front face. It leaves holes where the water runs, and rust stains.
- No kick at the drip. Water runs back under the metal onto the fascia instead of dripping free.
- Covering rotten fascia. The metal hides the rot until it spreads.
When to Call a Professional
Drip edge is a manageable job on a low roof with sound fascia. Call a roofer if the eaves are high, the fascia is rotten, the gutters are in the way, or the roof edge has complicated corners and dormers.
A roofer can also check that the drip edge, the gutter and the membrane work together, which is where most edge leaks start.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Fascia and Soffit service or the towns we cover.
How to Install Drip Edge: Questions
Does drip edge go under or over the underlayment?
It depends on the edge. At the eaves, the drip edge goes directly on the deck and the underlayment and ice and water shield go over it, so water runs onto the metal. At the rakes, the underlayment goes on first and the drip edge goes over it, so wind-driven rain cannot get under the metal. The two edges are opposite.
Do you install drip edge before or after the felt?
At the eaves, before: the drip edge is fastened to the bare deck and the underlayment is laid over it. At the rakes, after: the underlayment runs to the edge and the drip edge is nailed over it. Both are installed before the shingles, in that order, so the layers lap correctly.
How far apart do you nail drip edge?
A common spacing is about every 12 inches along the top flange, and closer at corners and laps. Keep nails near the upper edge where the next layer will cover them, and not through the vertical face. Always check the manufacturer's instructions and the shingle maker's rules for your roof.
How much should drip edge overlap?
Overlap joints by about 2 inches, with the upper piece over the lower in the direction the water flows. At rakes the lap runs from the eave upward. Nail through both layers near the top flange. Different products specify different laps, so follow the instructions on the package.
Can you add drip edge to an existing roof?
It is possible, but harder. At the rakes you can slide it under the shingle edge and nail it, and at the eaves it has to go under the underlayment, which usually means lifting the first course of shingles. The best time is during a re-roof, when the deck is bare and the layers can go on in the right order.
Related Guides
All Roof Edges, Fascia and Soffit guides|The full How-To Library
This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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