Various implementations include a system for coupling a post to a foundation. The system includes a rod having a first rod end and a second rod end. The first rod end is spaced apart from a top surface of the foundation, and the second rod end is coupled to the foundation. The post has at least one side wall at least partially defining an inner cavity and an inner tube disposed within the inner cavity and coupled to the at least one side wall. The inner tube has a first tube end and a second tube end that is closer than the first tube end to a bottom end of the post. A portion of the rod is disposable within the inner tube such that the first rod end is axially spaced apart from the first tube end. The first rod end is couplable to the first tube end.