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Pieces of ledger Z-flashing, laps and flashing tape for a deck ledger, with the cost.
With these inputs:
| Result | Value |
|---|---|
| 10 ft flashing pieces | 2 |
| Flashing run | 16.3 ft (1 lap) |
| Rim tape (11 in × 50 ft) | 1 roll · 16.3 ft |
| Flashing cost | $34.98 |
| Minimum metal thickness (DCA 6) | 0.019 in nominal |
| Run | 16 × 12 + 2 × 2 = 196 in |
| Pieces | 1 + ceil((196 − 120) ÷ (120 − 4)) = 2 |
AWC DCA 6: flashing must be corrosion-resistant metal at least 0.019 in nominal thick, or an approved non-metallic material, and aluminium should not touch preservative-treated lumber (copper in the treatment corrodes it). Laps and end runs follow Decks.com's ledger flashing guide (at least 4 in and 2 in); Trex's guide uses 3 in laps. Default price: Tamlyn BL325-PR 10 ft galvanized ledger flashing at McCoy's, $17.49 on 1 Oct 2026.
Where a deck ledger bolts to a wood-framed house, the IRC requires corrosion-resistant flashing so water can't get behind the ledger and rot the band joist. Enter the ledger length, the flashing piece length and the lap. The calculator counts the pieces with the laps and end extensions, the self-adhering tape for the ledger face, and the cost.
Yes. The IRC (R703.4) requires flashing where a deck attaches to a wood-framed wall, and the AWC's DCA 6 deck guide calls for approved corrosion-resistant flashing at any ledger board connection to a wall of wood framed construction, run continuously along the ledger.
The ledger length plus about 2 in past each end, with at least 4 in of lap wherever two pieces meet. A 16 ft ledger needs 196 in of run: one 10 ft piece covers 120 in and the second, lapped 4 in, covers the rest — two pieces.
Galvanized or stainless steel, copper, or a non-metallic flashing. DCA 6 says aluminium should not be in direct contact with preservative-treated lumber, because the copper in the treatment corrodes it. Metal flashing must be at least 0.019 in nominal thick.
At least 4 in per Decks.com's ledger flashing guide; Trex's guide uses 3 in. Seal any joint that laps less than 4 in with sealant, and run the flashing at least 2 in past each end of the ledger.
Tape is not a substitute for the metal flashing, but self-adhering butyl tape on the ledger face and over flashing seams adds protection. Trex Protect's 11 in × 50 ft rim tape is sold for rim joists and the ledger; one roll covers a ledger up to about 49 ft with the end runs.
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