Why Door Timber Rots
Doors face more moisture stress than almost any other timber in a home. External doors deal with direct weather exposure — rain driving against the frame, water pooling at the threshold, morning condensation sitting on the bottom rail. Sliding doors have their own vulnerabilities: the track sits at floor level where debris collects and moisture is trapped, and the timber sill beneath the track is completely hidden until it fails.
In Bayside Melbourne, the salt-laden air from Port Phillip Bay accelerates timber degradation significantly. Paint that would last a decade inland might crack in four or five years near the coast, opening up the underlying timber to moisture penetration.
What I Repair
- Door jambs — the vertical members either side of the opening
- Door frames — full frame rebuilds where rot has spread through multiple members
- Sliding door sills and tracks — the most common and most overlooked failure point
- French door bottom rails — constantly exposed to ground splash and moisture pooling
- Threshold timber — the piece at ground level that bridges interior and exterior
- External door casing — the decorative surround that also keeps water out
How I Fix It
I work back to sound timber every time. No surface filling over active rot — that's a short-term cosmetic fix that hides the problem until it comes back worse. Damaged timber is cut out and replaced with H3 treated pine, shaped to match the existing profile.
Where there are voids or transitions between new and old timber, Parchem Builders Bog is used to fill and feather — it sets hard, sands clean, and gives a seamless paintable surface.
Before I leave, I'll also check the drainage situation around the door. If there's a grading issue or a blocked drainage channel that's been sending water toward the frame, I'll flag it — fixing timber without fixing the water source just means the same repair in three years.
Sliding Door Rot
Sliding door sill rot is worth calling out specifically because it's often invisible until it becomes a significant structural problem. The aluminium track sits on top of timber, hiding what's happening underneath. If your sliding door has become hard to open, if the track is sinking, or if you can see paint cracking at the base of the frame — get it looked at. The earlier it's caught, the simpler and cheaper the fix.