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Deck height in relation to termite barrier

Hi There,
I am planning on building a low deck in an area surrounded on 3 sides by external walls of my house. The walls are brick veneer with the usual termite barrier two bricks up form the footings.
My question relates to the finished height of the deck in relation to the termite barrier. The deck wont be attached to the house (no ledger r any fixings) and there will be a 30-40mm gap between the edges of the deck and the walls. The doorway out on to the deck has a finished step about 30-40mm above the termite barrier. Ideally I want the decks finished height to be level with the doorway step but I am unclear of the regulations around this and I cant find them anywhere.
Thanks for you advice.
Cheers,
Cameron

Question by:
Cameron Nobes's picture
Cameron Nobes

Hi Cameron,

Thanks for your question and apologies for the delay in getting back to you.

The short answers are:

  • Australian Standard 3660.2 - 2000 Termite Management - In and around existing buildings and structures - Guidelines provides some information. However, unimpeded access, which permits regular and complete termite inspections of all elements between the ground and termite susceptible materials in the building, is the key to managing termite risk.
  • The Building Code of Australia Volume 2, Part 3.4.1 provides information about subfloor ventilation. Reduction in subfloor ventilation, caused by the proposed deck, may need to be addressed as inadequate subfloor ventilation is very conducive to termite activity.

We also consulted with Tyrells builders who provided a more comprehensive answer below. 

Regular termite inspections are the single most effective termite management measure, on the condition that inspection access is unimpaired to all subfloor termite barriers (termite capping) and to the base of external walls (e.g. not impeded by vegetation or equipment like air-con cabinets or hot water system or bridged by attachments such as steps, porches, decks, downpipes, gate posts and the like). In fact, regular termite inspections are essential to the satisfactory performance of all types of termite barriers be they physical capping, chemical treatments, baiting systems, whose main purpose is to reveal (otherwise highly secretive) termites to visual inspection.

So the proposal to maintain a gap between the deck edges and the walls overcomes the issue of the deck being above the termite barrier as it maintain inspection access. The width of the gap should be increased if there is any doubt about the adequacy of inspection access.

The other aspect about the deck proposal is any affect on subfloor ventilation. If a reduction is likely, especially if subfloor ventilation is already minimal, alternate means of creating air movement may be required. The avoidance of ‘dead air pockets’ is crucial to minimising the risk of termite activity. Consider alternate or larger subfloor vents or the introduction of mechanical ventilation if this aspect is of concern.

Hope this helps.

The BUILD team.

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