Termite Management for Builders Print E-mail
Article Index
Termite Management for Builders
Termite behaviour
Termite Risk Management Requirements in the BCA
Other Statutory and Legal Implications
Termite Management Standards
A Focus on AS3660.1
Sub-floor Ventilation Requirements
High Risk Sites Require Special Attention
Creating a Manageable Process
- 1: Assessing Site Risks
- 2: Assessing and Acting Upon Design Risks
- 3: Selecting an Appropriate Termite Management System
- 4: Quality of System Installation
- 5: Preventing Problems During Landscaping, Paving and Site Works
- 6: Handing Over to the Building Owner
What is the Risk of Major Damage from Termites?
Appendix A - Termite Resistant Timbers
Appendix B - State Variations to the BCA
Appendix C - Termite Management System Handover Form
References, Acknowledgements and Disclaimer

Sub-floor Ventilation Requirements

Sub-floor ventilation is often a forgotten part of termite management. The BCA (Vol. 2) requires the sub-floor between a suspended floor and the ground to be ventilated. This minimises sub-floor moisture which helps to prevent timber decay, and creates an environment that discourages termite attack. To be effective, acceptable sub-floor construction must:

  • Be free of building debris and vegetation
  • Provide cross ventilation,
  • Contain no dead air spaces
  • Be graded to prevent ponding and be above the external ground level
  • Have evenly spaced openings

Unless full underfloor physical or chemical barriers are provided (refer Fig 4 to 8), sub-floor clearance must be provided to enable regular inspection.

Where required, sub-floor clearance must be a minimum of 400 mm to the underside of bearer, except on sloping sites where part of the area may be a minimum of 150 mm clearance as shown in Fig. 9.

The amount of ventilation depends on the location of the site in Australia. This is governed by relative humidity; the relevant zone can be read off Map 1. Using Table 1, select the appropriate climate zone and read off the required ventilation area per metre of subfloor wall. Amounts vary depending on whether a sealed impervious ground membrane is used or not.

  Table 1 (Source: BCA 2007)
  Minimum sub-floor ventilation
(mm2/m of wall)
Climate
Zone
No impervious
membrane over
sub-floor ground
 
Sub-floor ground
sealed with
impervious
membrane
 1 20001000 
 2 40002000
 3 60003000


The sealed ground membrane option assists where special consideration is required for sub-floor ground which is subject to excessive dampness or frequent flooding. Care must also be taken to ensure patios, paving and similar construction does not limit the effectiveness of ventilation. Further details are in the BCA.

Image
Map 1: Climatic zones based on relative humidity (Source: BCA 2007)
Image
Fig 9: Minimum underfloor clearance - Refer to AS3660.1
 



 
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