It is perfectly natural for timber buildings to “breathe” as they react to weather and ambient temperatures. Because the dense timber at the heart of a knot expands and contracts at a different rate to the surrounding grain, tiny gaps can occasionally open up.
When moisture tracks along these timbers, it can find these entry points and eventually exit at the corners of your building. While this is a common characteristic of solid timber structures, it is straightforward to resolve.
1. Identifying Problem Areas
Before beginning repairs, you need to pinpoint the source of the ingress. Look for the following signs on your external walls:
- Visible Gaps: Small openings within the heart of a knot or between the knot and the surrounding wood.
- Water Stains: Discolouration or damp patches directly around or trailing below a specific knot.
- The “Corner” Effect: Note that water often enters through a knot but tracks along interlocking grooves, finally appearing in the corners of the room.
2. Tools & Materials Needed
| Item | Purpose |
|---|---|
| Sandpaper | For prepping the surface and smoothing the filler. |
| Knot Sealer | To seal the knot (e.g., Ronseal or similar). |
| Wood Filler | To plug the gaps and prevent further ingress. |
| Preservative/Paint | Base and top coat (e.g., Sikkens) to match your finish. |
3. Step-by-Step Resolution
Follow these steps to seal the affected area and prevent future leaks:
- Prep the Surface: Sand the knot and the immediate surrounding area externally to remove any old finish and ensure a clean bond.
- Apply Knot Sealer: Paint on a specialised knot sealer. This prevents the natural resins in the knot from bleeding through and helps stabilise the area.
- Fill the Gaps: Once the sealer is completely dry, apply wood filler to any visible gaps. Ensure the filler is pressed firmly into the openings.
- Smooth the Profile: After the filler has cured (refer to the packaging for drying times), lightly sand it back until it is flush with the timber wall.
- Refinish: Apply a base coat followed by a top coat of your preservative paint or Sikkens finish to ensure the area is weather-proofed and matches the rest of the building.
Note on Pre-emptive Treatment: Not every knot will cause a leak, so it is often more practical to treat them as they manifest. However, if you prefer a “belt and braces” approach, you can pre-emptively treat knots during your regular maintenance cycles to minimise future occurrences.