The layout of the fortress also followed the standard for a legionary fortress with wooden buildings inside a square defensive boundary. These defences originally consisting of turf ramparts on a green wood foundation, were built by the Ninth Legion between 71 and 74 AD. Later these were replaced by a clay mound with a turf front on a new oak foundation, and eventually, wooden battlements were added which were then replaced by limestone walls and towers. The original wooden camp was refurbished by Agricola in 81, before being completely rebuilt in stone between 107 and 108. The fortress was garrisoned soon afterwards by the Sixth Legion, possibly as soon as 118.