conditions conducive to timber pests

Top 5 Conditions Conducive to Timber Pests

When inspecting your home for timber pests, your inspector will note evidence of the presence of timber pests and any damage they have caused. Another important aspect of the inspection is taking note of any Conditions Conducive to Timber Pests. These are defects in the home or elements in the design that increase your homes susceptibility to timber pest attack.

Here are the top 5 Conditions Conducive to Timber Pests we find in our inspections-

  1. Poor Subfloor Ventilation

In homes with a timber sub floor, adequate ventilation is critical to the health of your home. Poor subfloor ventilation leads to a damp, dark environment which is conducive to fungal decay and attracts termite activity. Check out our blog post on Subfloor Ventilation for more helpful information on improving the ventilation in your home!

  1. Plumbing Leaks

Plumbing leaks create elevate moisture in timber elements of the home. When an timber element reaches a moisture content above 20%, it is already considered to be in a state of decay. The moisture also provides termites with a source of water to sustain activity in the home. Keeping on top of plumbing leaks in the home is essential to the health of your home. If you see any sign of active leaks, contact a licensed plumber to ensure it is rectified as a matter of priority.

  1. Improper Discharge of Hot Water and Air Conditioner Drains

We often find air conditioner drains and temperature pressure relief valves from hot water services discharging close to the home’s foundations. This creates an environment of constant moisture close to the home providing conditions for fungal decay and attracting termite activity. Check out our blog for more information on TPR Valves, there is also a great VBA Technical Solution Sheet on Air Conditioner Water Discharge.

  1. Inappropriately Stored Timbers

Building debris sored under the home and firewood stored near the home are another common issue found in inspections. Untreated timber stored around the home structure or utilised as garden edging provide foraging termites a food source close to the home. Once termites become established close to the home, there is an exceptionally high risk for activity inside the home. We recommend storing timber away from the home and off the ground.

  1. Timber Building Elements in Direct Contact with the Ground

A common element of design we find in inspections that is conducive to timber pests is veranda posts that are in direct contact with the ground. The direct contact with the ground promotes moisture which encourages fungal decay and termite activity. Termites can then make their way through the timber elements of the veranda and in to the home undetected. We recommend installing veranda post to metal stirrups to provide a gap between the timber structure and the ground.

Subfloor Ventilation

Subfloor Ventilation

High levels of moisture in the subfloor area of a home can lead to a number of issues including fungal decay and increased risk of termite attack.

In sub floor areas with poor ventilation water can pool or moisture can escape from the soil which increases the humidity in the subfloor space. This in turn increases the moisture content of timbers in the sub floor area. When the moisture content of timber is above 20%, it becomes more susceptible to fungal decay and termite attack.


In Gippsland (Climatic Zone C), the minimum subfloor ventilation openings is 6000mm2 per meter of wall. Vents should be evenly spaced and a vent should be placed no more than 600mm in from each corner.

A practical example of this is a common Pryda 230×165 Vent. As this vent provides 14157mm2 of ventilation, the maximum spacing for this vent is 2.36 meters.

Clearance Requirements for Subfloor Ventilation 

For inspection purposes, a ground clearance of 400mm is required between the finished ground level and any structural components such as bearers. For sloping sites, the minimum clearance may be reduced to 150mm as long as it is within 2m from an external wall.


Subfloor clearance requirements


The ground under a suspended floor must be graded to prevent water pooling under the home. This means low areas must be filled so they are higher than the external adjacent finished ground level.


Other Impacts on Subfloor Ventilation

Materials stored under the home impact the efficiency of sub floor ventilation. As well as blocking airflow in the sub floor, stored items containing wood increase the risk of timber pest attack.

Vegetation and garden beds against the home commonly impede the subfloor ventilation of homes. While garden beds against the home can enhance the visual appeal of the home, it is important to ensure sub floor vents are not impacted.

Where the subfloor space is excessively damp (from high water tables) or subject to flooding, the BCA offers 3 options.

  • Subfloor ventilation is increased by 50% (to 9000mm2 per meter of wall); or
  • The ground in the subfloor space is sealed with an impervious membrane; or
  •  Durability class 1 or 2 timbers or H3 (above ground) and H5 (below ground) treated timbers must be used.
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