Flame-shaped arches are not as strong as ordinary pointed arches. It is never used for making a vaulted roof. If this shape is used to make a doorway, there is generally another stronger arch around it. Another way is to make a square topped door that has Flamboyant decoration over the top. In France there are many doorways, both in churches and in houses, that are like this. They are rare in England but there is one at Rochester Cathedral.