Deck Flashing - Why It's Important

Often when we are replacing a deck, we discover siding, sheathing, and framing rot at the ledger board. More often than not, missing or degraded flashing is the culprit. Properly installed flashing prevents water from infiltrating the house behind the ledger board and rotting out the sheathing and framing. Wood rot behind a ledger board is often very time-consuming and expensive to repair.

Deck flashing, sometimes referred to as “Z” flashing, can be made of aluminum, copper, galvanized metal or PVC. Aluminum and galvanized flashing tend to deteriorate over time in the Outer Banks environment, while copper and PVC are more durable. When installing deck flashing, it is important that the flashing extends 4” up the exterior wall and that the house wrap is installed OVER the flashing. Because water runs downhill, it is critical that any lapped joints in the flashing do not face uphill.

Missing or improperly installed flashing can lead to problems beyond wood rot. While it’s an uncommon point for deck failure, when the ledger fails it generally causes the deck to pull away from the house. This type of deck failure can be catastrophic.