How to Frame a Door Opening

Add 2-1/2" to the width and 1-3/4" to the height of the door, not the door "frame". Example: a 36"x80" door would need a R/O (rough opening) of 38-1/2"x81-3/4". First install two studs with an inside to inside measurement of the R/O, then put the header in place and nail it with 8 (16-D nails) on each side.

Add in all the stud/header jacks. They should be put under any load point that might be above and they should be 16" or 24" on center. Use whatever layout is on the wall being built. (These days 16" centers are almost always used for building walls.) If the door is over 6' wide you should add an extra 3" to the header measurement (that is 3" wider than the R/O). Add two header jacks on each side. If you are using wide trim around the doors you should pack out the sides by adding a few 2x4's on the "King Studs".

Level both header jacks on the inside of the R/O. Cut the plate between the header jacks. Add a piece of 3/4" treaded lumber caulked on the bottom, side and along the bottom plate of the wall where they meet. Add flashing if needed.

Place the door in the center of the hole, add shims first in behind the hinges, checking for level. Adjust the door as needed to make the gap around the door and the frame equal. Nail or screw the door frame in place.