Fire door

An insulated fire door comprising:

• a door shell having spaced first and second exterior panels, a first vertical door edge and a second vertical door edge opposite the first door edge;
• a first gypsum panel between the first and second exterior panels;
• a plurality of first spacers bonded across an interior side of each of the first and second exterior panels, the spacers extending inward from the first and second exterior panels and contacting the first gypsum panel;
• the spacers maintaining the first gypsum panel in a spaced position from the interior sides of the first and second exterior panels as the door bows during a fire on one side of the door, until the gypsum disintegrates;
• a lock pocket for receiving a lock, the lock pocket disposed adjacent the second door edge;
• a second gypsum panel disposed below the lock pocket and a third gypsum panel disposed above the lock pocket;
• and
• a stiffener extending vertically within the door between the interior sides of the first and second exterior panels, the stiffener disposed adjacent to the lock pocket away from the second door edge;
• wherein the first gypsum panel extends horizontally from the first door edge to the stiffener, the second gypsum panel extends horizontally from the stiffener to the second door edge and the third gypsum panel extends horizontally from the stiffener to the second door edge.