Strips of membrane material that seal the critical joint where a horizontal roof deck meets a vertical surface like a parapet wall, curb, or column. It ties directly into the field membrane and runs up the wall, forming the primary waterproofing layer before being protected by metal counterflashing.
Heard on the job
Run the base flashing up the parapet at least eight inches above the roof line.
Related terms
Counterflashing
Flashing set into the wall above a base flashing, overlapping it downward to shed water off its top edge.
Flashing
Thin sheet metal or membrane installed at joints and interruptions in a wall or roof to direct water back outside.
Cap sheet
The topmost layer of a multi-ply roofing system that protects the underlying membrane from weather and traffic.