There are several squashy armchairs in each of the common rooms at Hogwarts.
"They all scrambled through it [the portrait hole] - Neville needed a leg up and found themselves in the Gryffindor common room, a cosy, round room full of squashy armchairs" (PS7)
"They had the dormitory to themselves and the common room was far emptier than usual, so they were able to get the good armchairs by the fire" (PS12)
"'What are you doing?' said a voice from the corner of the room. Neville appeared from behind an armchair, clutching Trevor the toad..." (PS16)