Deck flashing creates a barrier to prevent moisture from entering the house in the openings you create when attaching your ledger board connection.
You can buy flashing either in roll form or in rigid Z or L shaped 10' sheets made of stainless steel, copper or vinyl material. Never use galvanized steel or aluminum flashing in contact with an acq pressure treated wood ledger board because it will corrode. Vinyl flashing may not work as well in area with extreme temperature fluctuations. If you are installing copper flashing from a roll make sure you use copper nails to secure it into place to prevent corrosion. Copper works well because it is compatible with the chemicals used in commonly sold acq treated lumber and is easy to bend. Because flashing comes in different widths make sure your flashing will be the right size to tuck up behind the house siding at least a couple of inches. We recommend that you install a bead of silicon caulk to fill any openings.