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Why Termite Treatments Fail
There are few things more disheartening than paying a small fortune for the treatment of termites in your home, and then discovering that termites have recurred. With a modern brick home on concrete slab, the reasons can be varied, with some being improper treatment in the first place. An attention to detail is absolutely essential with termites being able to freely work within 10mm of soil treated using modern termiticides.
Termites can enter a modern brick home on concrete slab through the area between the top of the footing, and the finished soil surface (90% +), through the slab/footing joint, through the slab itself if it is cracked, or through the foundation itself if the home has been built with some foundation imperfections. The drawing below shows a cross section of a typical brick home, and how termites can enter the home.
The exterior perimeter of a home can typically be treated by trenching to 50mm below the footings, removing all mortar muck (excess mortar), and replacing the soil against the home with a sandy loamy soil that retains a termiticide well, treating as the soil is backfilled. Specific label compliant volumes and strengths need to be a achieved, but an area treated in this manner with the right termiticide will produce a long term result.
The mortar muck is a real issue in modern termite treatment, with the mortar muck able to prevent the chemical forming a full and continuous barrier, and termites have been found running in the cold joint that forms between the foundation and the mortar muck after residual treatment above. It is an issue that has now been recognised by both the Building Services Authority and the Queensland Building Tribunal.
Things get a little more complicated where slabs are laid against the home. We have no positive method of confirming that all the mortar muck has been removed from under a slab, and in some instances, we can recommend the concrete slabs be broken and removed to allow effective treatment. This is becoming more common with older homes that were protected using organochlorine chemicals (very forgiving from a treatment perspective). In the instances of modern homes with newer chemical barriers (post July, 1995), we can reach the conclusion that an effective termite barrier wasn't formed during construction.
Slabs can be treated using a drilling and injection technique, but in doing so we are assuming an ideal soil medium is under the slab that will retain the termiticide effectively. We are also assuming that there aren't material under a slab that will prevent the chemical from forming a full and continuous barrier. This is also an issue with soil perimeters treated using a rod injection technique. We all know what ASSUME stands for. We are at a point we cannot guarantee treatment by a drilling and injection technique. Where drilling and injection treatment is required, we prefer to treat using BASF's Termidor, which is non-repellent. By the label, it doesn't have the expected protection period of Biflex, but we believe it has a much better chance of producing a result in these situations.
The diagram above shows what can happen with mortar muck remaining on top of the footings.
Slab/footing failures typically occur where soil has pushed down on to of the footing during the concrete pour, preventing a full concrete to concrete joint forming. In the photo below, once the soil was washed away, we could reach under the slab by hand and retrieve bedding sand from under the slab. If I can fit my hand in there, a termite doesn't exactly have to duck it's head! Slab/footing joint and slab failures are difficult to retrospectively with any surety, as we cannot be positive that there are not materials under a slab that prevent the chemical forming a full and continuous barrier, despite being drilled and injected at termiticide label compliant rates.
Things get more complicated again with slab/footing joint failures where kitchen cupboards etc extend the distance we have to drill and inject away from the termite entry point. We are reaching the conclusion that drilling and injecting with modern chemicals in this instance cannot positively prevent termites from entering through this entry point.
We are fast developing a preference for retrospective Granitgard or Termimesh installations in slab/footing joint failures. An average home may cost $8 - 12,000.00 to protect. This involves removing two layers of bricks right around the home, and installing Granitgard or Termimesh.
In the event of a foundation failure, chemical treatment by normal methods is completely ineffective, and treatment by retrospective Granitgard or Termimesh is by far the preferred option.
For more information, please don't hesitate to contact us at any time. © Mark Porter 2001
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