By way of introduction, my friend Jonathan, a pest control owner in South Carolina, had this to say, “You must have had a slow day today. Snowed in?” Hahaha! As I told him, “That would have been a better excuse” for spending so much time solving one of the riddles of pest control.
About ten years ago I purchased & read a report from the National Pest Management Association entitled, “Research Report on Subterranean Termites”. There was one line that particularly stuck in my mind:
Often the thickness of the liquid termiticide layer applied to the ground of new construction before the pouring of a concrete slab (known in the trade as a ‘pretreatment’) is only about 1/8 inch.
A funny thing, in reflection of this fact, is an old news article a read a week ago. It was about a small handful of parents who were terribly worried about the deadly chemical layer being applied to the soil of their school to prevent termites. The funny thing is now you can see just how thin this layer really is. Once applied the chemical binds with the soil, and would be covered with concrete. Pretty much zero chance for anyone, especially the children, to ever touch that soil again without jack-hammering up the slab.
So, one-eighth inch, that’s not very thick, and this is when things are done according to the best standards (i.e. “following the label” of the product to be applied).
It’s easy to see how this thin fragile layer of protection can be disturbed and compromised by workmen walking on the newly treated layer, just work boots, or by the dragging of more metal rebar, running of new pipes, etc. This is why it’s a good idea for the workmen to cover the newly treated soil or gravel as quickly as possible with plastic on slab pours.
This afternoon, I decided to see if I could do the math to prove what I had read ten years earlier.
I can’t remember anything but basic math these days, even though I was once great with Algebra and Trigonometry, so I got lots of help from the internet. I found that 1 U.S. gallon equals 0.133681 cubic feet.
That 0.133681 cubic feet of termiticide liquid has to be divided evenly over the 10 square feet of soil or aggregate, according to the label: 1 gallon per 10 square feet to the soil under a slab.
I didn’t remember this, but apparently if you divide “cubic feet” by “square feet” you get just “feet”.
Following: 0.133681 cubic feet (volume) divided by 10 square feet (area) equals 0.0133681 feet (thickness of the liquid).
We need to convert decimal feet to regular fractional inches, and I learned that in this instance, since it’s less than 1 inch, I can do this by multiplying by 12, and then dividing by 1/16th or .0625 which gives 2.5666752 sixteenths of an inch. (0.0133681 x 12)/(0.0625) = approximately 3/16ths inch.
If you added too much liquid in one spot, and not enough in another, the thinner area might be close to that 1/8th inch figure.
Now this all starts to make sense why the finished volumes haven’t changed all these years on the label, only the percentages of active in a given volume.
According to the product label, if you are applying the chemical to gravel to be covered by a concrete slab, you are to apply 1 1/2 gallons, rather than just 1 gallon. At that volume, you’ve only got about 5/16ths thickness, or on the low side of error 1/4″.
Well, math withstanding, I still have some saying this about the chemical manufacturers, “I think the amount of chems they set for pre-treats is outrageous – They want to make more money! ”
Possibly, I’m sure the manufacturers want to make more money, but they’ve mostly done this by reducing the percentage of active ingredient in the concentrated product, and continually raising the price us applicators pay each year for those products.
What I’m talking about is coverage, even if you were the world’s biggest cheat, wouldn’t it make more sense to apply the correct volume with less concentrate? And no, I don’t advocate this, because these products were tested in the field at a certain part-per-million concentration, rate, and volume, and found to be effective only when applied in the manner described in the label. Anything less is unknown. Second only to material cost is labor, so those grossly under-applying termiticides on a pretreat are gambling that there will not be a problem or no one will care at the time.
The other reason you can’t double the volume & short the concentrate is because it’s against the label, and the inspector’s have the authority to pull tank samples, and are stepping up enforcement in the last couple of years. I am told that our oversight department in Kentucky has recently acquired new equipment to test tank & soil samples, and plan on doing so in 2011.
Why would you short-change yourself and the property investments of our future generations for just a few hundred bucks, at most, when there will never be another chance in history to do the job as well, or properly, as before the structure is built? …speaking from someone living in an 1887 building.