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Ledger Stains Band Board After Reflash Decision Tree

Troubleshooting Diagnostics Updated Jun 19, 2026 ยท Deck Building

Why this matters

You reflashed a deck ledger, and the rim/band board behind it still shows fresh staining. A wet band board at a ledger is the single most dangerous defect in deck building: ledger rot is the leading cause of catastrophic deck collapse. A stain reappearing after a reflash means water is still reaching the band, and the new flashing is either bypassed, misordered, or not the actual leak path. This tree isolates whether the water is coming over the top of the flashing, behind it, around a penetration, or from condensation, so the second repair stops the water instead of hiding the symptom for another season.

Symptom presentation

Read the stain before opening anything:

  • Vertical streak below the deck surface line, worst at the top of the band: water is coming over or behind the top flashing leg.
  • Stain concentrated at door thresholds or low points: threshold pan or sill flashing, not the ledger flashing.
  • Stain at bolt or lag locations: penetration leak around fasteners.
  • Diffuse damp/musty band with no clear streak, worst in cold weather: condensation from interior, not exterior rain.

Probe the band with an awl at the worst stain. Soft, punky wood means active or chronic wetting; firm wood with surface tannin staining may be historical.

Quick checks

  1. Confirm flashing layering. The wall water-resistive barrier (WRB) must lap OVER the vertical flashing leg, and the flashing must tuck UP behind the WRB and cladding, then turn out and down over the ledger top. A reflash that tucked the flashing on top of the cladding instead of behind it sheds water behind the ledger.
  2. Check for a cap/Z-flashing over the ledger top with a drip edge clear of the band, and a kick-out or end dam where the ledger meets a wall return.
  3. Inspect penetrations. Every lag/bolt through the flashing needs a sealed boot or sealant; an unsealed hole in new flashing leaks immediately.
  4. Look for a gap behind the ledger (spacers/standoffs) and weep path. A ledger fastened tight to wet sheathing with no drainage gap re-wets even with good flashing.

Isolation tree

Start with where the stain peaks.

  • Stain at the top of the band, streaking down: water over or behind the top flashing. Go to the flashing-layering branch.
  • Stain at thresholds/doors: go to the threshold branch.
  • Stain radiating from fasteners: go to the penetration branch.
  • Diffuse, cold-weather, interior-side: go to the condensation branch.

Flashing-layering branch:

  • WRB laps UNDER the flashing leg (flashing tucked over the housewrap/cladding): reverse lap. Water runs behind. This is the most common post-reflash failure. Re-detail so WRB and cladding lap over the upturned flashing leg.
  • WRB laps over correctly but no cap flashing over the ledger top: rain wicks into the ledger top grain. Add Z/cap flashing with a drip clear of the band.
  • Cap present but ends open at wall returns: missing end dam/kick-out. Water sheets behind at the ends. Add end dams.

Threshold branch:

  • No pan flashing under the door sill: door water is dumping behind the band. Install a sill pan and integrate it above the deck flashing. This is a separate leak from the ledger flashing.

Penetration branch:

  • Fasteners through flashing unsealed: seal each penetration with butyl/compatible sealant or boots. Confirm corrosion-rated fasteners; a leaking lag also corrodes and loosens the ledger connection.

Condensation branch:

  • Interior moisture, no exterior streak, cold-weather pattern: this is condensation, not flashing. Address interior vapor/air sealing and ventilation. Re-flashing will never fix it.

Confirming diagnosis

  • Flashing layering: do a top-down water test. Run a hose at low volume across the cladding above the ledger for 10 minutes and watch the band interior with a moisture meter. A rising reading confirms an exterior over-flashing path.
  • Penetration: isolate by taping over the suspect fasteners and re-running the hose. If the stain stops, the fastener was the path.
  • Condensation: meter the band on a dry, cold day with no rain for 72 hours. A wet band with zero recent rain confirms condensation.

Remediation

  • Re-detail the flashing in correct order: continuous corrosion-resistant flashing turned up behind WRB/cladding, WRB and cladding lapped over it, cap/Z-flashing over the ledger top with a drip edge clear of the band, and end dams/kick-outs at returns.
  • Provide a drainage gap behind the ledger with standoff washers/spacers so any incidental water weeps out rather than soaking the band.
  • Replace any band/ledger wood that probes soft; do not flash over rot. Re-verify the ledger connection (bolts/lags) is sound and corrosion-rated after the band is dry.
  • Install a sill pan at door thresholds, integrated above the deck flashing, as a distinct detail.

A rotted ledger or band board can fail without warning under load and cause a collapse. If probing finds soft wood at the band, ledger, or fasteners, shore or close the deck and treat it as a structural repair, not a flashing touch-up. Verify ledger fastening to a sound rim per IRC R507 before reopening.

References

  • IRC R507.2 and R507.9 (deck ledger connection, flashing, and band-board attachment).
  • AWC DCA6, Prescriptive Residential Wood Deck Construction Guide (ledger flashing and connection details).
  • AWPA U1, Use Category System (ledger and band-board preservative requirements).
  • ASTM E2112, Standard Practice for Installation of Exterior Windows, Doors, and Skylights (flashing integration and pan-flashing principles).

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