This photo shows how Termites have breached an Antcap (physical barrier) and gained access into the interior of the house. Physical barriers are great if they are regularly checked for termite workings and if they are in good condition.
At least 6-12 monthly termite inspections are strongly recommended of all physical barriers by a qualified Pest Technician.
It is also encouraged that home owners also keep an eye out regularly for any termite workings & ensure their barriers are kept clear & maintained. Remember, if in doubt, call your local BPI for further advice.