Subfloor moisture: the silent stump killer

Ask anyone who's replaced ten thousand stumps what kills them and you'll get one word: water. Managing subfloor moisture is the cheapest foundation insurance you can buy.

How moisture destroys foundations

• Rots timber stumps from ground level down — the invisible zone.
• Rusts ant caps, opening the door to termites.
• Feeds reactive-soil movement: a chronically damp side of the house swells while the dry side shrinks — differential movement, the worst kind.
• Corrodes even concrete stumps' internal steel over decades ("concrete cancer").

The usual suspects

1. Blocked or painted-over vents — the classic. Garden beds, paving and renders slowly bury them.
2. Downpipes discharging at the base of the wall instead of to stormwater.
3. Ground levels raised above vent line by decades of garden topping-up.
4. Leaking showers and taps quietly watering the subfloor for years.
5. No vapour barrier on permanently damp ground.

Fixes, cheapest first

• Clear every vent this weekend — free, and often transformative.
• Extend downpipes to discharge away from the house: under $100 in parts.
• Fix plumbing leaks — check the water meter with everything off.
• Add vents or fans where rooms were extended over old vents: a few hundred dollars.
• Ground/vapour barriers for chronically wet blocks: quoted case by case.

We check ventilation and moisture on every free inspection — because restumping a house without fixing the water is treating the symptom and reselling the disease.