The answer to 'what causes carpenter ant' is that carpenter ants are attracted to moist, decaying wood in and around homes. They build nests in this wood, tunneling through it to create their colonies. Carpenter ants do not actually eat the wood, but rather use it as a place to live and raise their young.
Carpenter ants are often found near sources of moisture like leaky pipes, roof leaks, or damp wood. They may also be attracted to wood that has been damaged by other pests or water. Identifying and eliminating the source of moisture is key to preventing and getting rid of a carpenter ant infestation.