The NRCA isometric flashing detail for thermoplastic membranes,
TP-6 Base Flashing for Non-wall-supported Deck, sometimes is
referred to as a field-fabricated "roof-to-wall" insulated
expansion-joint detail. The detail shown is used where a structural
roof deck is not supported by a perimeter wall. An example of this
would be a steel frame building with precast "tilt-up" exterior
This detail accommodates independent deck and wall movement.
There are several necessary elements in this flashing detail to
make it work successfully in the field. First, the thermoplastic
base flashing sheet should not be adhered completely to the roof
membrane or wall. Instead, the flashing sheet should be adhered to
the wall and roof membrane up to where the sheet contacts the
flexible foam rod. This allows the base flashing sheet to
accommodate differential movement between the roof and wall. The
flexible foam rod also acts as a water diverter, much like a cant,
elevating the base flashing sheet in the corner to direct water
away from the roof/wall intersection.
Another key element is installation of a flexible vapor retarder
and compressible insulation. The primary purpose of insulation and
a vapor retarder sheet is to limit heat loss and prevent moisture
condensation. A secondary purpose of the sheet is to hold the
compressible insulation in place and prevent it from sliding down
Log in or register for FREE access to this article and other Professional Roofing online content.