I do think treatment makes some sense. I am more up on the construction and real estate related issues than prevention.
There are evidently two types of termites or perhaps it is two different life stages of the same critter. In any case, there is the subterranean type, these live in the mud and crawl up the walls to eat the studs and those that fly into the attic and such places and enter unpainted or poorly maintained trim areas, under roof shingles etc. Sounds like you might have the subterranean type at the patio. You want to kill them for sure. I have poured bleach in the nests and any accessible areas and believe to have set them back a little that way. I think, but am not sure, that with the nest destroyed the guys left in the wall die.
It might not be a bad idea to have your parents get a couple of inspections, w/o tipping off the termite co’s chosen, that you are getting more than one inspection .Unfortunately, the public, including myself, is at a bit of a disadvantage when it comes to dealing with termite companies. The inspectors evidently have x-ray vision and can see dollars in the walls. Kind of kidding, you just have to watch what they are doing and ask for complete explanations.
