If your home has a raised floor — as many original Gold Coast homes do — the space underneath it does more work than almost any other part of the building. A dry, well-ventilated subfloor protects the structure above it. A damp, stagnant one quietly undermines it.
What poor ventilation does
When air cannot move through the subfloor, moisture from the soil has nowhere to go. Over time that persistent humidity supports fungal decay in bearers and joists, corrodes ant caps and fixings, and — most significantly in our climate — creates exactly the warm, moist environment subterranean termites seek out. Across 68 of CYTE's own inspections, confirmed termite activity or damage appeared in 16 properties — about 24% — and 14 of those 16 were standalone houses, mostly established ones. That termite risk is one of the reasons a damp, poorly ventilated subfloor is worth taking seriously long before any termite evidence shows up.
What we look for
- Blocked, undersized or painted-over vents around the perimeter
- Garden beds, paving or rendering built up over vent openings
- High moisture readings and musty, still air in the subfloor
- Stored materials and debris restricting airflow
- Evidence of fungal decay or timber pest activity in the accessible subfloor
Subfloor findings are a regular feature of inspections on older homes, and the remedies are often simple — clearing vents, removing stored timber, improving drainage. The inspection report records what was observable in the accessible areas, giving you a clear maintenance list before small issues become structural ones.
Subfloor moisture is closely linked to two other topics: read our guide to site drainage and stormwater and our article on five ways to reduce termite risk. Our FAQs cover more on inspection scope.
What does the inspector actually do under the house?
Under a raised floor the inspector checks the timber carrying the house, the fixings holding it together, the ant caps, moisture in the timber and the ground itself. Buyers rarely look there, so much of the inspection time on a raised-floor home is spent under it:
- Bearers, joists and the stumps, posts or piers carrying them, by eye and by sounding: a dull or hollow response to a light tap can point to decay or timber pest damage the surface does not show.
- Fixings, not just timber. The odd missing fixing bolt on a structural post is a finding we have recorded, and it cannot be seen from inside the house.
- Ant caps, checked for damage and bridging. They are an inspection zone, not a barrier: their job is to force termites into the open where workings can be seen.
- A non-invasive moisture meter over timber near the ground and beneath wet areas, so a damp bearer under a bathroom is a reading, not a guess.
- The ground itself: pooled water, soil graded towards the building and timber off-cuts in contact with the soil.
A floor that reads out of level on the laser inside is cross-checked against what is visible underneath. All of it is photographed and written up; the written report is the deliverable.
What happens when the subfloor cannot be fully accessed?
It is recorded as a limitation, in writing, with the reason, and the uninspected area is never reported as clear. In a report prepared in accordance with AS 4349.1 and AS 4349.3, "not accessible" is a finding in its own right, not a gap to be glossed over.
The usual reasons are practical: no access hatch, clearance too low to crawl under part of the house, wet ground on the day, stored items in the way, or a highset built in underneath so the original subfloor now sits behind linings and a concrete floor. Where part can be entered, that part is inspected and the report describes how far access extended and what stopped it. Where none can be, the report recommends that access be arranged and the area inspected before you commit. Raise it with the agent and your conveyancer straight away.
The timber pest section also notes a higher risk of undetected timber pest attack where a subfloor could not be fully inspected, because subterranean termites come up from the soil, and timber close to the ground that cannot be seen is where attack can go unnoticed. Every visual inspection has limits; a good report tells you exactly where they were. Our guide to reading your building and pest report explains where the scope and limitations sit.
What does the report say when the subfloor is damp?
A damp subfloor is written up as a conducive condition, not a termite finding or a leak diagnosis. A typical entry: elevated moisture was recorded to the subfloor timbers beneath the bathroom; this represents a condition conducive to structural damage and timber pest infestation; further investigation by a suitably licensed and insured Plumber or waterproofing trade is recommended, and further assessment by a Timber Pest Inspector where relevant. Ground water rather than pipework shifts the recommendation to surface water drainage and stormwater disposal.
Other findings carry their own referrals:
- Fungal decay or timber pest damage to a bearer, joist or post: further assessment by a Structural Engineer and a suitably licensed and insured Builder, plus a licensed timber pest manager for termite damage. The extent of concealed damage cannot be established visually.
- A missing fixing bolt on a structural post: an installation defect was observed; further assessment by a suitably licensed and insured Builder is recommended.
- Restricted ventilation with no elevated reading: a conducive condition and a maintenance item.
In our own inspections conducive conditions are almost always present, usually because of moisture. A damp subfloor is a strong case for an annual building and pest inspection: conditions under a house change with every wet season, and the report is a snapshot of the day it was written.
Subfloor condition is assessed as part of every building and pest inspection. Call 0431 114 815 to book.
If you are buying, Gold Coast building inspections with CYTE include a timber pest inspection in the same visit, and what we observe in the accessible areas is set out in a written report the same day.