DIY Guide: Roof Flashing Techniques for Exterior Corners

Proper roof flashing is essential for preventing water infiltration at exterior corners, especially on dormers and other protrusions. Below are two foolproof methods for flashing exterior corners to ensure water is directed away from vulnerable areas, keeping your roof dry and leak-free.

1. Wrapped Corner Method (Common Method)

This is the most common method for flashing exterior corners. It’s quick and effective, making it an ideal option for most DIY roofers.

Steps for the Wrapped Corner Method:

1. Position the Flashing Under the Weather Barrier:
   • Start by placing the flashing under the weather barrier on the dormer. If you’re working on a masonry chimney, the flashing should be nailed as far up the roof as possible.
   • Cap flashing (counter flashing) should be inserted into mortar joints to cover the top edge of the flashing.
2. Run the Base Flashing:
   • Extend the base flashing 4 to 5 inches beyond the dormer and cut the top section to match the dormer edge.
   • Bend the flap of the base flashing down and nail it along the top edge. This will create a seal at the top of the corner.
3. Notch the First Step Flashing:
   • Cut and notch the first step flashing, leaving a 1-inch flap. Bend this flap around the front of the dormer.
   • Nail the step flashing along its upper edge, ensuring it’s secured.
4. Continue With Additional Step Flashing:
   • Continue layering the shingles and adding step flashing above the first layer, ensuring the flashing fits snugly along the dormer and covers any gaps.
5. Caulk the Joint:
   • To seal any remaining gaps, apply a thin bead of caulk over the leftover joint at the corner and along the bottom edge where the flashing meets the shingles. This will prevent water from seeping in.

2. Soldered Corner Method (Premium Method)

The soldered corner method is a more durable and long-lasting technique, as it eliminates the potential for leaks that can occur at caulked joints. This method is best if you want to ensure a completely waterproof seal, though it requires more skill and special tools.

Steps for the Soldered Corner Method:

1. Measure and Order Custom Flashing:
   • You’ll need to measure your roof slope and have a custom piece of flashing made to fit the corner. This flashing should be crafted out of a material that can be soldered, such as copper (aluminum and galvanized steel cannot be soldered easily).
   • If necessary, take your measurements to a sheet metal or gutter-making shop to have the custom flashing fabricated.
2. Lay the Soldered Flashing:
   • Position the soldered corner flashing around the corner, making sure it covers the base flashing and overlaps properly with the shingles.
   • Nail the flashing to the dormer near the top edge, ensuring that it stays in place.
3. Secure the Lower Edge:
   • In some cases, you may need to nail the lower edge of the flashing to keep it flat. If you do this, make sure to cover the nail head with a dab of silicone to prevent water entry.
4. Continue with Shingles and Step Flashing:
   • Add shingles over the flashing, and proceed with step flashing as needed to complete the water-tight seal.

Conclusion

Both methods effectively seal the corner and prevent water infiltration, but the Wrapped Corner Method is faster and more accessible for DIYers, while the Soldered Corner Method provides a more permanent, leak-free solution. Whether you choose the quick and reliable wrapped method or the durable soldered technique, both will help ensure your roof stays dry and protected from the elements for years to come.