Subfloor Ventilation FAQ — Forster

If you notice a musty smell every time you open up the house after being away, that's the clearest sign. Under the house, look for pooling water or damp sand, dark staining on the bearers, and vents that are less than half open to outside air. A subfloor inspection with a moisture meter will confirm it.

A basic vent replacement or unblocking job might run $200-$500. A single mechanical fan installed is usually $800-$1,500, and a full multi-fan system is typically $1,500-$3,000 - often a worthwhile investment for a holiday home that's rarely aired out. A moisture barrier adds roughly $15-$25 per square metre.

Usually, yes, and it's particularly effective for a holiday home that sits closed up between visits, since the fan keeps moving air through even when nobody's opening windows. It still needs correctly sized fans and clear vents to work properly - blocked vents mean the fan just recirculates stale air.

Replacing existing vents or adding extra ones in a wall generally doesn't need council approval, since it's maintenance rather than structural work. The National Construction Code sets minimum cross-ventilation requirements for suspended timber floors, which is the standard any new or replacement vents should meet.

Every couple of years as a baseline, but for a holiday home it's worth checking each time you have a maintenance visit, since blocked vents and mould can develop unnoticed over months of the house sitting empty.

Moisture doesn't attract termites directly, but a damp, still subfloor is exactly the environment they and timber rot prefer, and coastal areas like Forster already carry higher termite pressure than inland towns. Restoring airflow is a genuine part of protecting the structure.