Bruce W. Maki,
|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
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
||Since the floor in one room is already tiled, I
made a mark 1/4" below the door and cut the jambs with a
|Next, I prepared the rough opening. Using a 4 '
level, I checked the plumbness of the framing on the hinge
||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.
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
||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
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
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.
- 4' Level
- 2' Level
- 2" Pneumatic Nailer
- Fine Tooth Saw
- Try Square
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