Typical signs
- Soft, stringy or easily crushed wood.
- Localized blistering paint, open joints and black or grey discoloration.
Where it is often found
- Bottoms of posts, thresholds, fascia, window sills, cladding corners and decks.
What it can mean
- Repeated water entry, missing flashing or poor drip detail.
- Insufficient ground clearance, splashback or deferred coating maintenance.
What to check next
- Probe without causing unnecessary damage.
- Check the detail above: joints, flashing, slope and contact with water.
Reasonable immediate actions
- Avoid simply painting over it; remove unsound wood and treat the cause.
When to stop and call a professional
- Involvement of a structural member, extensive hidden decay, complex envelope opening or mould at the same time.
Prevention
- Flashing details, ground clearances, coating maintenance and compatible sealants.