Thread: Underslab termite treatment

Hi Guys

I'll be having a 180m2 slab layed in a few weeks time and will need to have underslab termite treatment, Part A and perimeter treatment Part B. I've spoken to a few termite treatment companies and as expected they all recommend thier own methods and chemicals. However, today speaking with the concrete contractor he said if the area is spayed they will leave the site for 3 days, because of the chemical hazard. That started ALARM BELLS RINGING!. This slab is an extension on my existing house where I live with my wife and three young kids, last thing I want is any exposure to dangerous chemicals. I'm looking for more information on the net at the moment but hoped that you guys can add some advice and your experience to the issue.

The slab is a continuous slab on ground construction (500mm deep beams) connecting to the existing house slab using a series of 12mm bars. There are just a 4 plumbing pipe penetrations through the slab to contend with.

Any suggestions?

Thanks
Mike

What's been put under your existing house?

What's been specified for the new slab?

Whilst termite companies may call their product some fancy name the main ingredient (possible only 2 types) will be common to all.

I dont know what was under the existing slab. Its 20 years old and I have only lived here 1 year.

Nothing has been specified for the new slab yet, thats what I'm working on. A few companies suggested Biflex, for underslab spraying Part A, but it seems to me now that a barrier, rather than a chemical would be a better option. Its my understanding that if I use a barrier then I need to apply it to the 4 pipe penetrations and also the slab join. Would that be right?

Google Termi mesh, they may be able to help without chemicals.

Originally Posted by Bedford

Google Termi mesh, they may be able to help without chemicals.

...correct me if I am wrong, but I heard Termi-Mesh has failed in a few instances.
I would use a physical barrier in your circumstance.

Originally Posted by wolften

...correct me if I am wrong, but I heard Termi-Mesh has failed in a few instances.
I would use a physical barrier in your circumstance.

Termi-mesh is a physical barrier!

Hi Mike

I had my slab poured and pretreated (with Biflex) a couple of weeks back. Grano workers sat around and waited for the termite sprayer to do his job, let it dry a bit (which it did rather quickly) and then did their thing, i.e wrapped in black plastic.

Having said that biflex is classified as a poison last time i checked so I wouldn't let the kids near the sand after spraying.

Would think the residual levels in the sand would be pretty harmless but the poisoning center would know best.

This is a slab on ground. In the project home builders the "premium" treatment is termimesh. That says to me that the other treatments are not as good.

I have used Kordon in the past and it works pretty well.

I don't think you need to spray chemicals under the slab, you just need to stop the entry points above. Where the two slabs meet and the penetrations are critical points. Termimesh/Kordon will only be effective in the penetrations where they are in the concrete.

At the junction of the old and new I would look into a termicide paste filler type product. It works by the fact they can't eat it and it bonds to the concrete to stop them pushing it out.

It the slab is a traditional raft slab (sounds like it) I would also look into Kordon around the perimeter.

In summary, do not use under slab chemicals, use either Kordon or Termimesh at the penetrations and around the perimeter and a termicide sealant at the junction. There shouild be little increase in risk to your family and the termite protection would be sufficient.

Of course I am an engineer not a termite specialist but I have seen it many times before.

Chemicals are used with Termi-mesh anyway on new work, are you insured for termite damage if you are then the entire underslab will need to be treated wtih chemical and a certficate from a registerd pest controller supplied other wise they will not cover a claim

Hi Guys

Thanks all for your replies.

I did some hunting on the internet and contacted a few different suppliers, so its time for me to give something back to the forum. Heres my feedback.

For a slab on ground there are two stages to the termite treatment required to satisfy the building inspectors (in Victoria at least).

Part A.

This is an underslab treatment that has to be prepared before the slab is poured. It is intended to prevent termites entering the property from under the slab. There are two ways to aproach this treatment and they are a Chemical Barrier or a Physical Barrier.
The simplest way is probably the Chemical barrier. An installer simply turns up after the slab excavation and sprays the pads and trenches before the damp proof membrane is layed. Biflex seems to be the most common chemical and seems to have a 10 year effective lifespan. As Kinnean commented above, it can be done quickly and the concreters can continue work after the spraying, however my concreters insited that they would have to leave the site for a few days after spraying. That was their safety policy, and to be honest, with three young kids that totally put me off the chemical sprays.
The other option for Part A treatment is a physical barrier. The slab itself acts as a physical barrier to termites as long as the concrete strength is 17Mpa or greater, and most slabs are. Termites can still enter via the slab though through small gaps around pipe penetrations and between slab joins, if they exist. To combat this entry, additional physical barriers have to be applied to the penetrations and the slab joins. Termimesh is traditionally the most popular physical barrier, but there are others that perform in a similar way such as Kordon, Smart Film and Homeguard. These are simply plastic membranes impregnated with termicides. All the physical barrier mentioned here are installed to the slab joins and pipe penetrations prior to pouring the slab.

Part B

Part B is a perimeter termite prevention treatment. Its intention is to prevent termite entry from termites rising up the edge of the slab and finding their way in through the walls (brick cladding in my case).
Again a Chemical barrier is by far the simplest approach, with the perimeter of the property being sprayed after construction. Again Biflex is common. I found quite a few suppliers of Part B treatment saying that they couldn't guarantee the effectiveness of the treatment since if the perimeter soil is disturbed (ie through gardening or soil washed away with rain) then the barrier would be incomplete. OK, that maybe something you can control, but for me again, I'm not keen on the Chemicals with three young kids.
Part B treatment can also be accomplised using Physical barriers. Again Temimesh, Kordon, Smart Film and Homeguard can be applied. They are placed under the bottom plate of the timber frame and then cross the cavity and are terminated in the brickwork below the weep hole course. The barrier works by preventing termites that enter below this course of bricks getting any higher and accessing the timber. However, termites that migrate up the outside of the wall past the barrier can still gain access to the home, but in this case they have been forced to do so by moving up the outside of the wall and their mud tunnels will be visible, therefore is is necessary to maintain a regular inspection to insure that any breaches of the perimeter barrier are found before too much damage occurs. And this brings me onto a little know termite barrier that can be used for Part B, and that is the slab edge. Australian Standards recognise 75mm of exposed slab edge as being an acceptable Part B termite barrier. The 75mm of slab edge must obviously be above ground and it must be a clean floated/finished surface. It cannot be rendered or painted. The idea again is that the termites have to come out of the ground to cross it and regular inspections will detect them before damage is done. The draw back with this though, is that hardly anyone including my engineer, concreter,and various builders I have talked to knew of this method, and the concreter also said he would not be able to provide the smooth finish required because of the rough boxing, and preparing boxing to achieve the required finish would take a lot of extra time and money. So although a nice idea, its impractical and may look bad anyway.


Any of the above meet the Australian Standards and will get you a certificate, but you also need to consider whats best for you in the long term. Termimesh looks very good but is also expensive and you have to be realistic about what you are trying to achieve. In my case I have an existing 20 year old house on an existing slab. There is no physical barrier, and when renovating my bathroom I discovered I could put my hand down alongside the shower waste pipe straight into the soil beneath the slab. I'm not intending to rip up my existing house to apply termite barrier to every penetration, so that leaves me facing facts that I could spend a lot of money on termite protection for the new extensions to my house , but they can still enter through the existing slab and make their way into the extension unseen. For this reason many suppliers will not provide a warranty for treatment to an extension, and understandibly so. Those that do provide a warranty say that in the case of a claim thier inspectors will track the source of the infestation. If its breached their barrier they will pay out, if the source can be traced to stem from the existing house your on your own. But then thats fair.



I have 2 new slabs joining an existing slab on ground.

Slab 1 - 180m2 with 10m slab join and 4 pipe penetrations
Slab 2 - 21m2 with 7m slab join and 0 pipe penetrations
Total new slab perimeter for Part B - 60m


For Biflex Chemical spraying I was quoted
$4.23 inc. per m2 for Part A
$4.23 inc. per linear metre for Part B


For Termimesh I was quoted
$957 inc for 17m of slab join and 4 penetrations for Part A
The Temimesh supplier recommended Smart Film for Part B at a cost of $1095 inc. for 60m

Kordon was quoted at $22 inc per linear metre

For Homeguard I was quoted
Between $15.50 and $16 inc per linear metre used in Part A slab joins. Homeguard collars are extra for pipe penetrations and one company offered them free while another had a $390 charge.
Between $15.50 and $16 inc per linear metre for Part B


My Conclusion.

I choose Homeguard based on the price and the fact that it appears to be very safe. The installers infact used no gloves or special protection to themselves.
I used HomeGuard Blue for the Part A slab joins and will use it for the Part B perimeter barrier in a few weeks time. Homeguard collars were used on the 4 pipe penetrations.

They give me a 10 year warranty

Total cost for Part A and Part B = $1160 inc.


Hope this helps someone in the future.