How to create a drip edge and proper flashing around a shed roof
A well-installed drip edge and flashing keep water from infiltrating your shed roof, protecting the structure and extending the life of roofing materials. This short guide walks you through practical steps you can do in a weekend with basic tools and common materials. Safety and precision matter—measure twice and take your time to get tight seams and proper overlaps.
Step 1: Measure roof edges and overhangs
Measure the length of each eave and rake edge and note the overhang from the fascia; record lengths to the nearest 1/8 inch. Add 6 inches per run for overlaps and 10% extra for waste when ordering drip edge and flashing; accurate measurements reduce seams and callbacks.
[Illustration: person with tape measure across shed eave, notebook with numbers]
Step 2: Choose materials and gather tools
Select galvanized or aluminum drip edge and flashing in lengths of 8 to 10 feet, plus corrosion-resistant roofing nails or screws (1-inch to 1.5-inch), roofing sealant, metal snips, hammer, chalk line, utility knife, and safety gear. Buy one box of 1-inch roofing nails per 50 linear feet and one 10-ounce tube of sealant per 50 linear feet as a rule of thumb.
[Illustration: pile of metal drip edge, flashing, hammer, nails, sealant tube on plywood]
Step 3: Cut and pre-bend drip edge pieces
Use aviation snips to cut drip edge into measured lengths and, for rakes, bend the end at a 90-degree or 45-degree miter to match roof slope. Label each piece and deburr edges; neatly pre-fitting pieces on the ground saves time on the ladder and avoids gaps at seams.
[Illustration: hands cutting metal drip edge with snips and bending on a workbench]
Step 4: Install drip edge at eaves first
Starting at an eave, align drip edge so the flange sits over the roof underlayment and the small lip projects past the fascia by 1/4 to 3/8 inch. Fasten every 8 to 12 inches with roofing nails into the fascia or rafter tails, keeping nails about 1/2 inch from the top edge to prevent splitting; proper placement ensures water sheds past the fascia instead of behind it.
[Illustration: worker nailing drip edge into eave with ladder and measuring tape]
Step 5: Overlap and miter corners properly
When joining two drip edge pieces, overlap them 2 inches with the upper piece over the lower for eaves and reverse for rakes so water flows over seams. At rakes and valley intersections, cut 45-degree miters and butt them tightly, then seal seams with a 6-inch bead of roofing sealant; neat overlaps prevent capillary action and leaks.
[Illustration: close view of two drip edge pieces overlapped with sealant at a mitered corner]
Step 6: Install flashing along rakes and roof-to-wall junctions
Fit continuous flashing along rake edges and where the shed roof meets walls, sliding the top flange under siding or trim by 1/2 inch when possible and lapping upper pieces over lower pieces by 3 inches. Fasten flashing every 12 inches and seal the top edge with a continuous 1/4-inch bead of roofing sealant to block wind-driven rain; this redirects water away from joints and framing.
[Illustration: flashing being inserted under siding at roof-wall junction, caulking gun nearby]
Step 7: Finish with shingles and final seal
Install shingles or roofing material over the drip edge following manufacturer spacing, trimming so the shingles overhang the metal lip by 3/8 to 1/2 inch. Press a small bead of sealant at any exposed seams and check for loose nails after 24 hours; a final inspection after the first heavy rain ensures everything sheds water as intended.
[Illustration: worker laying shingles over drip edge, checking alignment with a ruler]
- Work from lowest eave upward so pieces overlap correctly and you avoid working over installed sections.
- Use stainless steel or hot-dipped galvanized nails in coastal or high-humidity areas to prevent corrosion.
- If the shed is taller than 10 feet, use a scaffold or two-person ladder setup for safer access to roof edges.
- Mark cut lines with permanent marker and re-check fit before fastening to reduce metal waste.
- Carry an extra 10% of materials for scrap and mistakes—buy slightly longer flashing lengths to minimize seams.
- Allow sealant to cure as directed (usually 24–48 hours) before subjecting seams to heavy water exposure.
- Do not install metal flashing in wet or freezing conditions; sealants often won’t adhere and metal can become brittle when cold.
- Avoid overdriving nails; pounding flush or countersinking metal will distort the drip edge and create paths for water.
- Never work on a roof alone; always have a partner and use fall protection for roofs steeper than 6/12 pitch.
- Do not trap underlayment under the flashing—always maintain the correct underlayment overlap to the drip edge to prevent water being wicked back under roofing materials.
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