What is flashing on a deck ledger?
Flashing is a metal or membrane strip installed along the deck-to-house connection to prevent water infiltration into the ledger board and rim joist.
The ledger board connection is where a deck attaches to the side of your house, and it is one of the first places water causes damage. Flashing is the metal or membrane material installed at this joint to redirect water away from the rim joist and band board underneath your home's siding. Without proper flashing, water seeps behind the ledger, saturates the wood, and causes rot that compromises both the deck structure and your house frame.
Flashing typically comes as aluminum or galvanized steel L-channel that sits under the house siding and over the deck rim board, or as peel-and-stick membrane tape that bridges the gap. The material must overlap the siding above and extend past the rim board below so water runs off rather than pooling. Poor flashing installation or missing flashing is the root cause of most ledger failures in older decks across the Charlotte area, where humid summers accelerate wood decay.
When hiring a deck builder, confirm that flashing will be installed correctly during initial construction or repair. Proper flashing extends the life of your deck structure and protects your house from costly water damage. If you're buying an older home with an existing deck, check the ledger connection for gaps, separation, or deteriorated siding around the attachment point, as these are signs that flashing has failed or was never installed. Custom deck design-build providers in Greater Charlotte can assess your ledger and recommend flashing upgrades if needed.