Cutouts in the membrane allowed it to slip over the tops of the posts, minimizing seams; an open cutout at the outside corner column accommodates the membrane turn-down along both edges.
The upper edge of the first sheet of membrane is screwed to the deck at 12-inch intervals. A preprinted line 4 inches from the edge marks the correct overlap for the next sheet.
Turned-down membrane edges are secured to the PVC fascia with double-sided tape approved by the TPO manufacturer.
Seams at inside corners leave a potential pinhole leak where the deck and walls intersect.
A prefabricated corner piece is heat-welded to all three surfaces.
Peel-and-stick membrane flashing adhered to the sheathing serves as a counterflashing. It will later be covered with housewrap.
Square-sectioned flashing boots are temporarily secured with provided band clamps before being welded to the deck with the heat gun and roller.
The orange-handled tool next to the post is a pointed probe that’s run carefully along welded seams to pinpoint any missed areas. The boot’s overlapping split side — which allows it to be wrapped around a continuous column — is welded closed. The open top of the finished boot will be covered with flexible flashing.