Joist tape is a thin, waterproof adhesive material that creates a barrier against water, air, and moisture infiltration. It is applied to the tops of deck joists, beams, and ledger boards to protect the decks substructure from weathering and moisture. Joist tape is also referred to as flashing tape and is used to prevent moisture penetration of joists, protect the lumber from rot, and extend the life of the decks substructure.

Joist tape is essential for the overall health of the deck and benefits you by saving you on future maintenance/replacement costs, increasing the anticipated life of your deck, and improving your decks structural integrity so you can enjoy your deck, worry-free, year after year.

There are two primary forms of joist tape: asphalt and butyl. Butyl-based tape offers the best protection and durability with the easiest installation. Joist tape is an affordable way to protect your deck substructure, and it allows the wood to breathe because it is applied as a cap.

When selecting the best deck joist tape, you should consider ease of installation and cost. Rubberized-asphalt-based deck joist tape performs equally as well by costing nearly 50 percent less than butyl-based tape. A high-quality deck joist tape or joist flashing tape, like PolyWalls Rot Shield Joist Tape, will protect the top of the deck joist, ledger board, and rim joist against rot and wood decay.