In short: Mould on roof timber is a symptom. In one Winter Valley house the causes were a drain discharging into the roof space, valley openings that let in storm water and a roof that was not drying out.
What was visible
Traces of mould were on roof truss members and on the eaves lining when we investigated this Winter Valley home in December 2025. Both point to prolonged moisture, poor ventilation or both.
A drain in the wrong place
The evaporative cooler's drainage pipe ran inside the roof space and its roof flashing was not secured. That set up had already leaked once and remained a risk to framing, insulation and ceilings.
Water from the valley
The tiled valley had several side openings that had let in rain during heavy falls. Tiles of a different type showed an earlier repair. Without closing the openings, the next storm could do the same.
Why cold weather adds to it
Ballarat's cold nights mean warm indoor air condenses on cold roof timber unless the roof space vents it away. Add a leak and the timber stays wet long enough for mould to grow. The report asked for the drain to be rerouted, the valley closed up and ventilation reviewed.
Written by our local inspection team from work carried out in Ballarat. Licensed building practitioners, Building & Plumbing Commission registration CDB-U 53425.
