An end dam is a flashing detail that blocks water at the ends of flashing to prevent leaks and moisture intrusion.

An end dam is a raised or sealed termination point installed at the ends of flashing components to prevent water from running off the edge and entering the building assembly. It is a critical moisture-control detail used in roofing, waterproofing, and window or door flashing systems.

In construction, end dams are commonly used with sill flashing at windows and doors, roof edges, balconies, and horizontal flashing conditions. They are formed by bending metal flashing upward at the ends or by installing pre-manufactured or field-applied end dam components. This detail forces water to drain outward instead of escaping laterally into wall or roof assemblies.

Properly designed and installed end dams are essential for long-term building durability. Without them, water can bypass flashing systems and cause hidden moisture damage, rot, or mold. Many building codes, manufacturer details, and best-practice guidelines specifically require end dams as part of effective water management strategies.

End dams are often hidden once construction is complete—but they’re one of the most important details for keeping water out of buildings.

• Ice Dam