Doors, Understanding Walk Through Openings
When it comes time to change out or install an opening in a wall- like a door, there are certain considerations that should be taken from the beginning. It’s a good idea to have measurements from or have the door and frame already purchased, so you can rely on those measurements while doing any work.
First, if this is part of any new construction project, the framework will already be exposed. This makes for easy modification of the studs. This is the easiest point in which to cut and install any opening for a passage, door, window etc.
Secondly, when the walls are finished, (drywall, plaster, paneling, etc.) there’s more work to be done.
Today, we will be referring to pre-hung interior doors, sold at most retail centers
When starting this project with finished walls, you will need to determine where the framework is inside the wall and cut into the wall to create an opening from top to bottom slightly larger than what you desire. Usually by one studs span (roughly 14 1/2″ – 16″) and then replace the stud at the correct spot to receive the frame of the door.
For strength, the opening (any opening) will need a header, which is a beam above the opening, usually a 4×4, 4×6, or larger, set with king studs and trimmers. King studs run the complete height from bottom plate to top plate.
You should see this if you opened up the wall correctly. Then the trimmer 2 x 4′s are the movable parts to set the door correctly with shims. The header sits just above the trim 2 x 4′s, nailed to the king studs and will have a cripple wall, above the header and in between the king studs.
At this point you will need to rely on the measurements from the door and frame that you are installing. Note: The header length should be slightly longer than the width of the door frame that receives the door.
Once you have the framework ready for the door frame, install the frame and door into the opening and plumb / level.