Prehung fire door unit with one or two swing door leaf or leaves

A system, comprising:

• a bay extending substantially vertically, wherein the bay includes a recess defined by an opening and an L-shaped base, the L-shaped base defining first and second surfaces disposed in perpendicular orientation relative to one another;
• and
• a fire door assembly, including:
• at least one swiveling door leaf including a front surface defining a plane orientated perpendicularly relative to the first surface of the L-shaped base in a closed position of the at least one swiveling door leaf;
• and
• a fixed frame made of a plurality of profile members including two substantially vertical uprights and a horizontal upper cross-member assembled end-to-end between the two substantially vertical uprights, each of the plurality of profile members made of an elongate and flat element of sheet metal and including a single L-shaped longitudinal fold, the at least one swiveling door leaf mounted pivotably to the fixed frame about a vertical axis by at least two hinges and the fixed frame fully inserted into the recess of the bay,
• wherein the single L-shaped longitudinal fold of each of the plurality of profile members enables complementary fitting of each of the plurality of profile members with the L-shaped base of the bay upon full insertion of the fixed frame into the recess of the bay, such that each of the plurality of profile members is fully inserted within the recess of the bay, and includes a first fold portion applied against the first surface of the L-shaped base of the bay in parallel orientation relative thereto, and a second fold portion spaced-apart from the second surface of the L-shaped base of the bay in parallel orientation relative thereto, wherein a distal end of the first fold portion of each of the plurality of profile members is co-planar with the front surface of the at least one swiveling door leaf, and
• wherein the fire door assembly is configured to be mounted in the bay.