Fluon painted in a continuous band over a smooth surface will stop ants. good for 6 to 12 months before you ned to paint it again. Same as for roaches, only a very thin coating.
If you can get the ant species identified, it would help. Some, such as Coastal Brown ants will take a granular bait called Amdro. They take it back to the nest and feed the Queen, killing her. It is not cheap but you can store it in the fridge and it will keep for years.
Other species can be excluded by a surface barrier spray around the building. Problem is, in high rainfall areas they don't last so long if exposed to the elements.
The Ag Dept can help with ID and the most effective method of control. Catch and freeze a few , wrap them in paper and deliver or mail to your nearest branch.
Blue