Unlike other building construction materials, old wooden structures often do not survive because they are more vulnerable to weathering and fires and are naturally subjected to rotting over time. Although now-nonexistent wooden residential towers, watchtowers, and pagodas predated it by centuries, the Songyue Pagoda built in 523 is the oldest extant pagoda in China; its use of brick instead of wood had much to do with its endurance throughout the centuries. From the Tang Dynasty (618–907) onwards, brick and stone architecture gradually became more common and replaced wooden edifices.