Standard interior house doors come in standard dimensions: 24 In. - 36 In. x 80 In.
prehung door unit: comes attached to its jambs with the hinges already in place
door blank or slab: just the door itself with no associated trim and sized to fit into the existing door jamb
Types of interior doors
Hollow core:
Solid core:
Solid wood:
Installation
Prehung Door Unit
The rough door opening should be 2" wider and 1" taller than the finished door dimensions. With the extra space you adjust and plumb your new prehung door assembly to square it up.
Measure the wall's finished thickness before purchasing a door. Prehung doors may come either with split or flat jambs.
Use a level on the hinge side of the casing to align it vertically. Tap shims into place between the door jamb and the rough framing to make the jamb plumb.
nail through both the jamb and shims into the wall stud near the top hinge using an 8d finish nail. Any nails that you drive through the jambs should also go through shims behind the jamb. Then the other hinges too.
Trim any shims that protrude from between the jambs and framing to allow the second jamb to be installed.
Nail through the center of the stop and jamb to secure the second jamb.