Abstract: A conjoint facia, flashing and water dam for use as a roof deck appurtenance is provided and includes dam means, and facia and flashing means, together contributing means having normally upper longitudinal laterally entrant grooved structure and normally upper longitudinally laterally projecting tongue means which are engaged for stabilizing the facia and flashing means horizontally, while upward thrust for maintaining the facia and flashing means in an installed position is transmitted by flashing means reactively upon exerting pressure upon a roofing sheet on the dam means, with facia means of the facia and flashing means being anchored.