> stopping termites from entering the building.

Do the termites in your location not fly? In Fiji we have termite swarms once a year. Millions of them will show up at every light they can get to in the evenings. Everyone is advised to turn off their lights for a few hours and light a fire outside so as to get the termites to kamikazi. These are the Asian Subterranean Termites that arrived here via Australia.

Pesticide in a ditch around a house isn't going to stop these buggers.