What is the purpose of deck flashing?

Deck flashing serves a crucial function in managing water associated with a deck installation. Its primary purpose is to divert water away from the deck ledger, which is the horizontal board attached to the house that supports the deck. When water collects at or near the ledger board, it can lead to rot and deterioration of wooden materials, possible structural damage, and the growth of mold or mildew.

By using flashing, typically made from metal or a waterproof membrane, the deck is effectively protected from moisture intrusion that could compromise both the structural integrity of the ledger and the wall it is attached to. Proper installation of deck flashing is key to ensuring that water runs off effectively, preventing long-term issues that could require costly repairs.

The other options do not adequately describe the functional role of deck flashing. While aesthetics can play a role in exterior construction, the primary function of flashing relates to water management. Similarly, holding the deck in place or providing insulation are not purposes served by flashing; these responsibilities are managed through different means, such as proper fasteners or structural supports.