I have never seen a door set with that big of a gap unless it was to get past floors that were not level.
Recommended space between bottom of interior door and floor.
Unlike interior doors gaps between a front door and a frame must go with the standards not so much due to the possible expansion of a leaf but because of the danger of penetration of cold air and extraneous.
To fix the issue the doors need to be removed bottom of the jambs cut and reset the door.
If a room is not equipped with a cold air return it should then have a transfer air grill installed between the room and adjacent hallway which may already have a cold air return.
Also referred to as net door size.
The standard i use is 1 2 over finish floors 3 4 is acceptable.
Check to see if your door will close over it by placing a small piece of it on the floor under the.
It has a protruding edge centered on the bottom that fills the gap between two different floors.
That is a lot of room for unlevel you have there.
Equal to the nominal door size minus design clearance.
The largest measured width by height of the door leaf as manufactured.
Between a leaf of interior doors and the floor it is required to leave a gap of at least 2 2 5 cm to provide natural ventilation.
Either way it gives you about 3 4 clearance over the finished floor.
If you are hanging a pre hung door on a bare subfloor you put the door right on the floor and install it.
Allowing a gap at the bottom of a door cannot support proper airflow.