supporting thickness for each door leaf application_number US 201013703194 A description the figures show a fire door assembly according to the invention which as a door leaf 1 intended to be mounted in a bay 2 which is specifically rectangular or square and which is made in a masonry structure 3 such as a wall extending substantially vertically in a building and specifically in a high security building said door assembly consisting on the one hand of a fixed frame 4 comprising substantially two vertical upright members 5 joined by a horizontal upper cross member 6 and on the other hand a door leaf 1 mounted pivotably about a vertical axis 7 by means of at least two loose joint hinges 8 the or each door leaf 1 optionally comprising a peripheral reinforcing or stiffening frame 9 said fixed frame 4 being capable of being at least partially inserted into a recess 10 made in the opening of said bay 2 and open towards the exterior thereof an opening of the recess 10 towards the exterior of the bay 2 is specifically understood to mean an opening towards the area of travel of one or each door leaf 1 according to the present invention the fixed frame 4 of such a door assembly is made of an assemblage of end to end profile members each of which is made of an elongate and flat element made of a rigid material having temperature and fire resistance properties such as rigid sheet metal optionally.