It's mandatory to build Barracks in the beginning of the battle, as they are required to produce Assaults, which are required to gather containers. In normal cases it is recommended to build 2 of them, regardless of your rank. The exception to this rule are very big and open maps like Whirlwind as the containers are usually far greater in number or more spread out or if you are planning to do an Assault Rush.

Barracks are very cheap buildings and can be used to stall opponent armies by building them in front of your units or other buildings. This works especially well against the AI and opponents who do not micro-manage their units, as they tend to focus on the closest target available.

It is also possible to build barracks on top of a minefield, therefore detonating the mines below its foundation (and getting itself destroyed). Please note that it only clears a 2x2 area at a time, which means that you pay 100 resources to clear 40 to 80 resources in mines. Therefore it is recommended to use Force Fire or Fortresses to clear it if possible.