Base flashing is a waterproofing component installed at the base of walls or vertical surfaces to prevent water intrusion.

Base flashing is a flashing material installed at the intersection of a vertical surface—such as a wall, parapet, or curb—and a horizontal surface like a roof or deck. Its primary function is to prevent water from entering the building by directing moisture away from vulnerable transition points in the building envelope.

In roofing and waterproofing systems, base flashing works in conjunction with counterflashing and membranes to create a continuous watertight barrier. It is commonly used at roof-to-wall connections, chimneys, mechanical curbs, and parapet walls. Materials for base flashing may include metal, modified bitumen, rubberized asphalt, or single-ply membranes, depending on the system design.

Proper installation of base flashing is critical to long-term building performance. Inadequate height, poor adhesion, or improper integration with adjacent materials can lead to leaks and premature system failure. Building codes and manufacturer specifications typically define minimum flashing heights, attachment methods, and overlap requirements to ensure effective water protection.

Many roof leaks occur not in the field of the roof, but at flashing details—making base flashing one of the most critical components of a roofing system.

• Aluminum Flashing
• Asphalt Base Course
• Base Isolation