Four fully grown, enormous, vicious-looking dragons were rearing on their hind legs inside an enclosure fenced with thick planks of wood, roaring and snorting - torrents of fire were shooting into the dark sky from their open, fanged mouths, fifty feet above the ground on their outstretched necks.
(Goblet of Fire, Chapter 19, The Hungarian Horntail).
A thought on the dragon enclosure in Goblet of Fire. It appears to be made out of wood. Dragons are, of course, fire-breathing creatures of huge destructive force.
Later, some stands (of an unknown material) are added around the enclosure. We do know, however, that also in the vicinity of the dragons are a tent where the champions huddle and the Forbidden Forest. All of these substances have one thing in common - they are highly flammable.
Rowling is aware that putting dragons and wood next to one another isn't a good idea and even has Hermione being sassy about it in an earlier book.
He looked very pleased with himself, but Hermione didn't.
"Hagrid, you live in a wooden house," she said.
(Philosopher's Stone, Chapter 14, Norbert the Norwegian Ridgeback).
Why would the Triwizard Tournament organisers (or any self-respecting grown-up) pick a wooden enclosure in the middle of a forest as a place to hold four fire-breathing dragons?