Hanging a door can be a frustrating process the first time or two. Taking time to check for plumb / square / level through the project will prevent frustration and achieve good results.
Removing an existing door
Take the door off the hinges or tracks.
Remove the door casing (trim) on both sides.
With a reciprocating saw or mini-hacksaw, cut through nails holding the jambs.
If the door has a threshold plate, pry or cut it loose.
Framing a rough opening
On exterior and load-bearing walls you'll be removing a few existing wall studs that support the house. Therefore, the door's rough opening framing must take over the load.
In most cases, 2×4 or 2×6 lumber is used for side framing and two 2x10s (or larger) lumber makes up the header. Mark the outline of the doorway- 6 "wider and 3" higher to accommodate framing. Make sure to remove any baseboard in the way.
Saw or chisel away the existing wallboard / plaster. Cut the existing wall studs in the new opening where the top of the framing header will be, or remove them completely if the header reaches the wall's top plate.
Remove the soleplate at the threshold. A reciprocating saw or hand saw is handy for this job. Cut two 2x4s (or 2×6) king studies to run the full length of the wall, or use an existing wall stud if possible.
Scab on trimmer studies to the king studs to support the header. Cut and fit the header on the trimmer studs and toenail the header to the king studs.
Installing door jambs
If you're putting in a prehung door, fitting the door into the jambs is already done for you. You just need to shim the jambs correctly into the frame. Whether you're installing each jamb separately, or installing a pre-hung door, getting the jams in place is basically the same way.
Shim the side jambs plumb / square with the opening and tack them in place. Test fit the header jamb and when it's square secure the side jambs.
NOTE: Place shims behind hinge and strike plate areas for secure fastening-especially exterior or locking doors.
Check for squareness again, shim if needed, and nail the header jamb in place.
Fitting the door
These are the extra steps needed if you do not have a prehung door. Compare the squareness of the jamb frame to the door. If it's not square or you're putting on an old door, it may be necessary to trim the door to fit.
TIP: Consider installing the door knob if it is not already. It can help you control the door while test fitting and handling. (For more on that, check out our Door Knob Tips.)
When the door and the jamb frame are square to each other, adjust the gaps between the door and jambs-typically 1/16 "at top, 1/8" on the knob side and up to 1/4 "on the bottom. installing carpet later, include that in bottom clearance.
Fit the door, block it with shims and check the gaps-plane the door if needed. When the door fits correctly, you're ready to mark the hinges.
Hanging a hinged door
Most doors have three hinges. A heavy or extra secure door may require more hinges. In this instance, we'll install the hinges to the jamb before fastening the hinges to the door. But some people screw them to the door first.
Mark and mortise the jamb hinges-usually 7 "from the top of the upper hinge to the top of the door, and 11" from the bottom of the lower hinge to the bottom of the door. Center the middle hinge.
Locate the hinges to stick out slowly from the jamb so they will not "pinch" when opening / closing.Fasten the hinges to the jamb. Then fit the door and trace around the door hinges pieces (hinge leaf). Mortise out the door and fasten the hinges.
TIP: Do not completely tighten the screws to allow the hinges some "play" while getting the hinges pins in.
Tap the door pins in and test the door. If it opens / closes freely, you're ready to put on the door stop and latch hardware.
A newly hung door may bind or sag a bit, due to a jamb being out of plumb. Or accidentally making the hinge mortise too deep creates an uneven gap along the latch side of the door.
Both of these problems may easily be corrected by shimming a hinge or two with a cut piece of cardboard, thin flooring scrap, or in some cases a shim cut out to fit behind of the hinge.
Close the door and check the gaps. If the door sticks at the top hinge, shim the top hinge and snug the bottom hinge, and vise versa for a door sticking at the bottom hinge.
If the door sticks at the top knob-side corner, tighten the top hinge and shim the bottom hinge, and vise versa for a door sticking at the bottom knob-side corner.
Remove the hinge across from the gap you wish to close. Place the shim in the mortise and reattach the hinge over it. Note how much the door gap changed and shim other hinges accordingly if necessary. However, shimming out too thick will often make the shim visible.
Door knob tips
Do not try to install a door knob without an appropriately-sized hole saw. Go buy one-and a good quality chisel for mortising.
Most knobs and latch kits have instructions and a handy template to use, so we will not discuss actual installation here. In most cases, the knob and latch are located 3 'from the bottom of the door.
With the knob on, locate the strike plate location by transposing the knob location measures. A less conventional method is to "color" the knob latch point with pencil lead, turn the knob to retract the latch, position the door shut, and release the knob to mark the edge of the strike plate on the side jamb.
Source by Michael Brennen