A subfloor inspection involves a qualified inspector accessing the space beneath a building's lowest floor to evaluate the condition of structural supports, check for moisture-related issues, and identify any evidence of timber pest activity. For properties with raised floors, the subfloor area is one of the most critical zones an inspector examines, as many serious building and pest problems originate or become visible in this space first.
What the Inspector Looks For
In the subfloor, the inspector examines bearers, joists, stumps, and any other structural timbers for signs of deterioration, including rot, fungal decay, and damage from wood-destroying organisms. They check for adequate ventilation, proper clearance between the ground and timber framing, standing water or damp soil, faulty plumbing, and the presence of debris that can harbour pests. Subfloor ventilation is particularly important, as poor airflow leads to elevated humidity that accelerates timber decay and attracts termites.
Access and Limitations
Subfloor access is not always possible. Many modern buildings are constructed on slab-on-ground foundations with no accessible subfloor. Where a subfloor exists, access hatches may be too small, obstructed, or absent altogether. Industry standards of practice generally require inspectors to note any areas that were inaccessible and could not be assessed. Limited access is a common inspection limitation that should be clearly communicated to the client.
Subfloor Conditions and Pest Risk
The subfloor environment directly influences a property's susceptibility to termites and other timber pests. Moisture pooling, earth-to-timber contact, and stored materials against subfloor timbers all increase risk. A thorough subfloor inspection often uses a moisture meter to quantify dampness in structural timbers.