Generally, termite flashing is very effective lasts forever and is the cheapest solution.If you want a prophylactic and also a condom (haha) use a bitumen layer between the slab edge and the flashing and also between joins and corners.here is a pdf from an Australian govt departmenthttp://www.bsa.qld.gov.au/SiteCollectionDocuments/Generic/Publications/Termite%20Management%20Systems%20-%20Advisory%2