Avoid Deck Rot with Flashing Tape - Pressure-treated lumber that stays wet will eventually rot. Flashing tape keeps water from getting trapped between doubled-up joists. If you're resurfacing an existing deck frame, tape over any joists that have a lot of holes from the previous nails or screws. Buy black tape if you can find it; shiny silver and white tapes may be noticeable between the gaps in the decking. The tape shown will be covered by the perimeter deck board.