Counterflashing

An inverted L-shaped metal strip built into a wall to overlap flashing and make a roof or wall watertight. A flashing turned down from above to overlap another flashing turned up from below so as to shed water.

Purpose

Counterflashing is used to prevent water penetration at the joints of roofs and walls, ensuring buildings remain watertight. It is a critical component in building construction and maintenance, protecting structures from water damage and leaks.

Examples of Use

1. Installing counterflashing on a roof where it meets a chimney to prevent water from seeping into the building.
2. Using counterflashing in conjunction with wall flashing to create a waterproof barrier at the intersection of a roof and a vertical wall.
3. Applying counterflashing during the installation of skylights to ensure that the areas around the skylight remain watertight.

Related Terms

• Flashing: A thin material, usually metal, used to prevent water penetration at joints or intersections in building construction.
• Drip Edge: A type of flashing installed at the edges of a roof to direct water away from the fascia and into the gutters.
• Underlayment: A protective layer installed under roofing materials to provide an additional barrier against water infiltration.

Notes

Proper installation of counterflashing is essential for its effectiveness. It should be inspected regularly and maintained to prevent leaks and water damage over time.