(07) 3219 2777
Why
the new termiticides can’t protect against some common building practices!
The article that some vested interests didn't want published!
Between
1954 and July, 1995, most homes in Australia were protected using organochlorine
termiticides (Dieldrin, Aldrin, Chlordane, & Heptachlor), which were very
effective in preventing termite attack when applied at Australian Standard
compliant volumes and labelled strengths. The organochlorines had a vapour
action in the soil, and would commonly stop termites from coming within up to a
metre of where they had been applied, and if properly applied in accordance with
Australian Standards had an expected protection period of
some 30-35 years.
In
July, 1995, the organochlorines were banned from use, and were replaced by an
organophosphate termiticide (chlorpyrifos), and a synthetic pyrethroid
(bifenthrin). Today, chlorpyrifos has a labelled expected protection period of
at least 10 years as an underslab treatment, and at least five years as a soil
perimeter treatment. Bifenthrin has a labelled expected protection period of at
least 10 years both underslab, and as a soil perimeter.
Neither
of these newer termiticides has a significant vapour or repellency action, and both
need ideal soils to bond in to achieve their labelled expected protection
periods. As a footnote, the manufacturers have been far from keen to let the pest
control industry know what soil mediums that they treated to achieve their
labelled expected protection periods. By these termiticides not having
significant vapour actions, termites will travel quite closely under or between
areas that have been treated. In treating existing homes using soil replacement
techniques with chlorpyrifos, where the mortar muck has not been completely
removed from the footings, termites have later been found accessing the home
through the “cold joint” between the footing and the mortar muck.
With today’s homes commonly built on concrete slab, the building industry has shifted to using the concrete slab as part of the termite barrier. In September, 1995, the Cement and Concrete Association of Australia published a ten page document titled “Concrete as a Termite Barrier – Pouring Slabs to AS 2870”. Key points of that document were effective vibration, curing, and not adding water to the concrete on site.
In the picture above, we have the concrete truck driver adding water to the mix, and the concrete pump operator adding water too! Result: Most likely up to 30% reduction in concrete strength according to data from the Cement and Concrete Association. For the concretors and builders, if you really want concrete at 100 slump, order it at 100 slump. It will cost just a little bit more, and you'll end up with the correct amount of cement in the mix, and your concrete is still easy to work.
At a recent meeting of the Queensland
Building Codes Board, it was resolved that vibration of the concrete slab should
be an option, and not mandatory.
WHY NOT
MANDATORY?
In
the photo above, clear lines are visible that indicate this slab has not been
vibrated effectively. The slab has been used as part of the termite barrier, and
it is quite likely this slab will crack along the visible “fault” lines. An
Australian Standard and label compliant chemical treatment to the perimeter of
this home will do nothing to prevent termite ingress through this potential
entry point. Even an Australian Building Codes Board accredited reticulation
system installed to the perimeter with the ability to be “recharged” would
do nothing to prevent termite ingress through this potential entry point.
In
brick on slab construction, with the slab is used as part of the termite barrier
with physical protection to the slab penetrations, and only a chemical perimeter
treatment, then a slab with footings and slab laid separately has a
potential fail point.
It is currently an approved construction method, but no
real protection is afforded to the joint between footings and slab.
In
this case, one can reach between the footings and the slab, and draw bedding
sand from under the slab. The line above the keys would indicate poor slab
vibration.
An Australian Standard and label compliant chemical treatment to the
perimeter of this home will do nothing to prevent termite ingress through this
entry point. Even an Australian Building Codes Board accredited chemical
reticulation system to the perimeter with the ability to be “recharged” will
do nothing to prevent termite ingress through this entry point.
A
number of major project home builders have adopted a practice that the chemical
barriers cannot effectively protect against, even if they are reticulated with
the latest Australian Building Codes Board accredited reticulation system, and
installed in an Australian Standard compliant manner. It has become a common
practice to place greased steel pins in the wet footings, that are later used to
hold the boxing or formwork for the concrete slab.
When
the concrete slab has cured, the steel pins and the boxing are removed, leaving
the slab formed on top of the footings.
If
the footing depth is sufficient to retain the pin, without the pin protruding to
or near the soil under the footings, this can be considered an acceptable
building practice from a termite perspective. Where reduced footing depths are
used, this practice is fraught with danger.
Major
project builders using this building practice are commonly building with
engineer approved footings as shallow as 200mm. We have found sites with this
building practice with footings as shallow as 100mm. If these pins continue to
the soil under, or sufficiently through the slab to produce cracking, then the
footing’s integrity is compromised. The deepest hole left by these steel pins
we have measured so far is 170mm.
This has to ring some alarm
bells with the regulatory authorities! They’ve had this information in writing
since August, 2000.
|
|
An
Australian Standard and label compliant chemical treatment to both
the underslab and perimeter will do
nothing to prevent termite ingress through this entry point. Even an Australian
Building Codes Board accredited reticulation system with the ability to be
“recharged” would do nothing to prevent termite ingress through this entry
point.
SO WHAT’S THE ANSWER?
Building
practices do not change overnight! If pest control operators (PCOs) are in the
business of protecting homes from termite attack, then they must visit building
sites during construction to gain an understanding of what is really happening.
Only when we know what is happening, can we design an effective termite
protection system.
The
Australian Building Codes Board has two accredited physical termite protection
systems for slab on ground construction. Granitgard graded stone barrier
achieved their accreditation in 1996, and Termimesh achieved theirs on the 4th
of August, 2000. By protecting the slab penetrations, and the outer brick
cavity, the physical barriers
can effectively protect
against the steel
pins through the footings.
|
|
Of
the two Australian Building Codes Board accredited physical barriers, we are now
forming a particular preference for Granitgard graded stone physical barriers.
Granitgard is a CSIRO developed graded stone barrier fitted to the slab
penetrations and outer brick cavity. It is small chips of granite that are too
heavy for termites to shift that pack too tightly for termites to fit between.
No chemicals or poisons are required. It is regarded as a true “life of
building” product, and we have found that Granitgard is difficult for following
trades to damage.
In some instances these issues
require Building Services Authority adjudication, and we are experienced in this
area. For more information, please visit our BSA
Case Histories Page. © Mark Porter 2000
Termite Issue Found Termites? Termite Inspections Termite Treatments
Building? Builders Building Practices Granitgard Thermographics Fire Ants
Commercial Pests Fumigation Consultancy Environpest Interesting Links
Termite Bait Boxes Opportunity Contact Us
Get it right the first time!
