Illinois Roofing License IDFPR #19HC00108700 · GAF Certified Contractor
Drip edge is L-shaped metal trim installed at the eaves and rake edges of a roof. It’s small, inexpensive, and required by the Illinois building code on every residential roof. But on older homes – and on cheap roofing jobs – it’s often missing or installed incorrectly, which causes fascia rot, water damage behind the gutters, and a host of other problems that don’t show up for years. This guide covers what drip edge actually does, the correct install sequence, and how to spot when yours is wrong.
What drip edge actually does
Drip edge serves three functions on a residential roof:
- Directs water off the roof and into the gutter (at eaves) – without drip edge, water can wick back under the shingle edge and flow behind the gutter instead of into it
- Protects the deck edge – the exposed edge of the plywood or OSB decking is vulnerable to water damage; drip edge caps it
- Provides a clean termination point for the shingles at the rakes (the gable-end edges of the roof)
It’s a small, simple component – typically a strip of bent aluminum about 5 inches wide along the eaves and rakes – but the function is critical. Without it, water finds the deck edge and rots out fascia, soffit, and decking over years.
Illinois code requirements
The International Residential Code, adopted by Illinois (IRC R905.2.8.5), requires drip edge installation:
- At eaves and rakes of all shingle roofs
- Minimum 3-inch lap over adjoining pieces
- Minimum 0.019-inch thick metal (aluminum is most common; galvanized steel and copper also acceptable)
- Extending at least 1/4 inch below the roof sheathing
This is non-negotiable for code compliance on new construction and replacement roofs. Building inspectors in Madison County check drip edge as part of the final roofing inspection.
The correct install sequence
Drip edge has to be installed in a specific order relative to the other roof layers – get it backwards and water defeats it. The right sequence:
At eaves (along the gutter line):
- Roof deck installed
- Drip edge installed directly on the deck
- Ice and water shield laid over the drip edge (so water flows over both)
- Synthetic underlayment over the ice and water shield
- Shingles on top
This sequence means any water that reaches the deck edge runs over the drip edge into the gutter. The ice barrier above the drip edge prevents water from wicking back behind it.
At rakes (gable edges):
- Roof deck and underlayment installed
- Drip edge installed over the underlayment (opposite of eaves)
- Shingles overlap the drip edge by ~1/2 inch
At rakes, drip edge goes on top of underlayment because there’s no gutter – water can flow directly off the roof at the rake.
Common installation mistakes
Drip edge installation errors we see during inspections of older or poorly installed roofs:
- Drip edge installed under the ice barrier at eaves – backwards sequence, allows water to seep behind the metal and onto the fascia
- Drip edge missing at rakes – common shortcut; rake fascia rots first
- Drip edge installed but not extending into the gutter – installed flush with the fascia, so water still misses the gutter and flows behind it
- Old drip edge reused during a re-roof – bent, corroded, or undersized drip edge that was supposed to be replaced was left in place
- No drip edge at all – common on pre-1995 IL homes that were built before strict drip edge code adoption
How to tell if your roof has drip edge
Stand at the corner of your house and look up at the eave edge. You should see a thin metal lip (~1/2 inch tall) running along the bottom of the roof, just above where the gutter mounts. If it’s there, you have drip edge. If you see exposed fascia board right up to the shingle edge with no metal trim, drip edge is missing.
Same check at the rakes (gable ends): look for a metal trim along the diagonal edge of the roof where it meets the gable wall. If shingles run all the way to the edge without a metal lip, drip edge is missing there too.
A free Trill Roofing inspection includes checking drip edge condition and code compliance on every elevation.
Cost and when to add it
For a typical 2,000 sq ft home, drip edge installation costs:
- As part of a roof replacement – included in the standard scope. No separate line item.
- Retrofit installation on an existing roof – typically $300-$700 depending on linear footage. Some shingle removal is required to insert the drip edge in the correct sequence.
If your existing roof is in good condition but missing drip edge, retrofit is worth doing – but only if the fascia is still sound. If the fascia is already rotted, you’re combining drip edge with fascia replacement, which adds significantly to the cost. At that point, evaluating the entire roof’s condition is often the right call.
Schedule a Trill Roofing inspection at /free-inspection/ – we’ll check drip edge status as part of every assessment.
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