There is often great discussion in the pest control industry about what products work and what products don't work, often the discussion is about termite barriers.
The problem with making statements like " 'X' termite barrier doesn't work because I saw infestation 'Y' " is that the limitations and scope of the barrier are seldom included in the statement.
The reality is that, for the most part, termite barriers DO work, the problem usually occurs in the installation.
Here are some prime examples of termite barriers that have been incorrectly installed.
A termite barrier is tucked underneath a bearer, allowing for undetected termite entry.
This barrier is hidden behind a pier, since it's not directly attached to the ant capping, termites could easily climb up behind the pier without being seen.
Once again, the barrier does not make it all the way out to an inspection edge under the bearer.