All of the buildings were designed and built by the Roman soldiers themselves, they were trained to do so and the army had its own skilled engineers who designed the wall. So much of the wall has survived and is a testament to their building skills. For example, when the Picts nearly destroyed the wall three times, but on every attempt it was rebuilt by the Romans. But For nearly 250 years, Hadrian’s Wall was being patrolled and guarded by top flight, soldiers right on the very outer edge of the Roman Empire.
After Hadrian’s death in 138, the new emperor Antoninus Plus basically abandoned the wall and built a more advanced wall called the Antonine Wall. But ultimately he came back to further advance the Hadrian’s Wall as the defense barrier.