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Deck Ledger Flashing Length Calculator

Calculate total ledger flashing length including end overhang (kick-out allowance) for a deck ledger board.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax
19.69 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Total flashing length needed

20.18 ft

High confidence

For the dimensions entered, expect a total flashing length needed of 6.15 m. Set for United States against IRC 2024. The market selector changes both the units and the code cited.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Flashing length = ledger board length + 2 x end overhang, providing a kick-out allowance to direct water away from the wall at each end of the ledger

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Frequently asked questions

Why does the flashing need to extend past the ends of the ledger board?
Extending the flashing past each end of the ledger (a kick-out allowance) directs water running down its face away from the wall, past the ledger's ends, instead of letting it run behind the siding at the joint where the ledger stops.
Is a bigger end overhang always better?
A larger overhang gives more margin against water tracking behind the siding, but the flashing still needs to be properly integrated with the wall's water-resistive barrier and siding at each end — check your local code and flashing manufacturer's details for the specific required dimension.
Does this calculate the flashing height or profile, too?
No — this calculates linear flashing length only. The flashing's height, bend profile, and integration with the ledger and siding are separate details that should follow your local code and manufacturer's installation instructions.