Before, thatched houses belonged to Normand peasants. They were made with what they found in the surroundings: straw ,reeds from the marshes, for the roof. wood for the framework , clay and straw for the walls. Near where i live, there is "La route des chaumières "( the thatched houses way, where you find most of it in the region.Now it costa lot to maintain this kind of house, before poor people lived in them , now it's the contrary!!!they were often located in the ereas close to marshes, now you can find them anywhere in Normandy.On top of the roof was some clay with Iris to maintain the structure.
I wish you a good day.