Deck flashing diverts water runoff in the face of the building away in the ledger board, that is the joist that is connected to the side of your residence. The flashing, made of galvanized or plastic steel, seldom corrodes, but it might get moldy. You will need to remove decking boards to mend it.
To prevent water from seeping behind the deck’s ledger board and rotting the board along with the siding, the flashing must cover the surface of the ledger board and bend over the border. The flashing utilized for this function is called Z-flashing; the opposite end of this “Z” goes beneath the siding. The decking boards usually cover the flashing, and that means you have to remove them to make repairs.
If the decking boards operate parallel to the siding, it is possible to simply remove the previous board to access the flashing. When the boards run perpendicular, you can avoid having to remove all of the boards covering the flashing by cutting off enough in the ends to find the flashing you will need to fix and filling the gap with a brand new board when you are done. Remove cracked flashing by prying it off with a pry bar; install new flashing by sliding one border below the shingles and securing the bottom edge of the shingles to the sheathing with caulk or roofing nails.