Almost all interior doorframes are made up of similar parts. At the top is the head jamb and this is flanked on each side of the door frame by a side jamb, one for the lock side and the other on the hinge side. The doorframes are installed in a “rough stud opening,” a hole in the wall framed by wall studs and a header.
Once the jamb is in place any design of door, or “slab” from colonial patterns to French doors can be installed using specific door knobs and hinges to match.
USE A QUALITY LEVEL
Having a good, 4" level is very important for a good installation. Check the accuracy by laying it on a flat surface and then note the position of the bubble. Now turn the level over end for end and re-check the bubble. The bubble should be in exactly the same spot. If not, get another level.
DOOR FRAME SIZE
The rough opening should be 2 to 2¾” wider than the door and 1" to 2" higher. All corners should be 90°. Add the width of the door slab to make sure that the combined door unit will fit in the door frame.
The width of an interior door slab (another name for just the door without the frame) varies between 24" and 36". Typically, 30" doors are used for every room in the house except for the door that leads to the basement where it should be 32" wide (or greater). Note that if you want to keep your washer and dryer in the bathroom, you should install a 32" door (or greater), if space allows.
When we talk about a 30" door, we are talking about the width of the door slab itself. The frame adds an additional 2" in width and 1" height. Standard doors are 80? high. You must allow a clearance of ½” between the bottom of the door and the floor.
Both the number of hinges used and their size depends on the type of door and how thick it is. Hollow core interior doors usually have two hinges while the heavier, solid-core doors should have at least three.
If placing the door between adjoining rooms that will have carpet or a hardwood added later on both jamb sides can be adjusted from 3/8" to 1" above the floor depending on the material that will be installed.
If you plan on painting or staining your door do so before you install it. By laying the door flat, the paint or stain will be much easier to apply and will not run or leave drip lines.