Repairs & Maintenance · 8 min read · Intermediate

Minor Timber Rot Repairs: When Filler Is and Is Not Appropriate

Repair small non-structural timber defects only after removing the moisture source and checking that the remaining wood is sound.

Key points & steps

Find and fix the water source first. Failed paint, leaking gutters, open joints, poor end-grain protection and trapped moisture can all cause the repair to fail again.
Probe the affected timber to establish how far softness/decay extends. Structural members, extensive decay or timber that no longer holds fixings securely should be replaced or professionally assessed.
Remove loose/decayed material back to sound timber and let the area dry appropriately before treatment or filling.
Use preservative, consolidant or primer only where specified by the repair system; do not rely on chemicals to restore missing structural strength.
Build the repair with a suitable exterior timber repair product, shaping it so water will shed rather than sit on the repaired area.
Sand and prime the cured repair as required, then restore the protective exterior coating system.
Inspect the repair periodically, especially at joints and horizontal surfaces where water can re-enter.

Filler is appropriate for limited cosmetic/non-structural loss, not for rebuilding a rotten structural support.
End grain and lower frame sections often decay because they stay wet longer than vertical faces.
If rot extends behind cladding or into concealed framing, open up enough area to understand the extent before covering it again.