The basic construction techniques and materials of log structures make them some of the most difficult dwellings to “bat-proof”.
This is primarily because log structures are full of uneven surfaces assembled with many joints and materials of varying densities (green logs, dried lumber, stone, brick, concrete, asphalt, clay, plaster, silicone, metals, etc.). While putting all of these materials together makes for some beautiful buildings; in many cases it also creates an excellent opportunity for bats to enter and take up dwelling there.
Additionally, as is true with most other residential and commercial structures, bat avoidance is rarely considered during the construction phase of log cabins. The large populations of bats in wooded, lake, river or mountain resort regions (where most log-cabins are located) is rarely given a thought until they invite themselves in.