Pre-hung door after installation. New Construction:

Installing A Pre-Hung Door

In This Article:

A pre-hung door is prepared and installed in the rough opening.

Related Articles:
Skill Level: 3 (Intermediate) Time Taken: About An Hour

By , Editor


First, I laid the pre-hung door on the floor, because I didn't have any sawhorses with me.


This was the rough opening, between the master bedroom and the bathroom.

First I made sure the floor was level in the doorway. If the floor was not level, I would need to cut one jamb taller than the other.


This door had thin strips of wood attached in four places. Each strip extended past the jamb, making it impossible to install by myself, as the nails go on the opposite side of these braces.


So I had to remove the braces.


My approach was to cut three braces to the exact width of the door jamb and fasten them to the jamb with small finish nails.


Door jambs had to be cut shorter. Since the floor in one room is already tiled, I made a mark 1/4" below the door and cut the jambs with a fine-toothed saw.


Next, I prepared the rough opening. Using a 4 ' level, I checked the plumbness of the framing on the hinge side.


I cut off some excess drywall compound so it would not interfere with the shims.


I fastened a pair of shims a few inches from the top. Then I set up another pair about midway down, adjusted them until the level showed perfectly plumb.

Then I fastened them with small brad nails. Using a pneumatic nailer really saves time here.


Ouch! At the bottom of the wall the framing is very warped, much more than my shims will correct.


So I had to make a custom shim that was much more severely tapered than anything in my tool box.

I had to check that the final shim pair was both plumb with the pair above and square with the wall. This kind of problem is time consuming and far too common.


Nailing pre-hung interior door to the framing.

Working from the outside of the door (the hinges are on the inside) I placed the pre-hung door in the opening, making sure the jamb was flush with the drywall. Then I drove in a single 2-inch finish nail, right through the top shims.

Next I checked the jamb for plumb (on the hinge side only) and drove another finish nail through each of the other two sets of shims.

This could be done with a hammer and conventional nail, but it would be awkward for just one person, because the door might shift as the nail is pounded in.

Some carpenters don't nail through the shims but nail right next to them. They say their method allows for adjustments after nails have been driven. I rarely have a need for further adjustments, and if I do, I pry the jamb away from the frame and rip the shims out. It seems that when I don't nail through the shims, they end up sliding down when I least expect it. But the main reason that I nail through the shims is that they are easier to cut off later because they don't wiggle while I saw them.

That third brace that I mentioned earlier... I put it right behind the door knob hole (on the hinge side of the door), so I could knock it out with a screwdriver.

But I left the other two braces in until everything was done.


I opened the door and drove another nail near each of the first three nails.

An analysis of the forces on door hinges reveals that the top hinge is being pulled away from the jamb, and the bottom hinge is being pushed into the jamb. This fact is what causes the uneven gaps above and below the top hinge.

At the top, the striker side of the door wants to rub against the jamb.


And on the hinge side the gap is uneven... wider below the top hinge than above the hinge.


So I usually add another set of shims just below the top hinge. I leave the shims a little loose (maybe 1/16" of play) and then drive a nail through. This sucks the jamb in and evens out the gap, and improves the tight gap on the striker side.


 From this point forward the installation is a finicky matter of making sure three things on the striker side look right:

1. The gap between the door and the jamb is uniform.

2. The door hits the doorstop (the narrow trim in the center of the jamb) properly, that is, uniformly from top to bottom. Many doors hit at the top first or bottom first.

3. The jamb is reasonably flush with the wall on both inside and outside. If the jambs are not close to being flush, installing the casing (trim) may involve shaving away a lot of drywall to let the board lie flat.

These last steps seem to take up about half of the time involved in setting a pre-hung door when I work by myself. There is a lot time wasted in checking the inside of the room for uniform gap then checking outside to see how the door hits the stop. I usually install shims and nails at five places along the striker jamb, checking carefully at each point. Having a helper inside the room would quicken the pace, as long as they know what to look for.

There is probably no easy verbal explanation for this final process.

If the hinge side of the jamb is hung plumb, then adjusting the striker side is mostly a process of trial and error. I start a the top and work downward. If I made a huge mistake I could cut all the nails with my reciprocating saw and start over.

The last step is to cut off the shims that stick out beyond the door jamb. If the protruding shim is really thick, I use a fine-tooth saw. Otherwise I score the shims with a knife and snap them off.


The finished door looked respectable after the homeowner installed the trim.

Tools Used:

  • 4' Level
  • 2' Level
  • 2" Pneumatic Nailer (optional)
  • Fine Tooth Saw
  • Hammer
  • Try Square

Materials Used:

  • Pre-hung Door
  • Shims
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Copyright © 1999, 2003

Written June 29, 1999
Reformatted June 9, 2003