How To Install A Prehung Door
Summary: Knowing how to install a prehung door is important to get the job done right. If you don't follow these tips, your prehung doors could rub, not close properly or open by themselves. Prehung door installation requires the proper size door, the correct hand and shims.
DEAR TIM: I need to know how to install a prehung door. This door is a regular interior door, not an exterior door. Is this job as easy as the salesman made it out to be? I am suspicious, as it seems that you need some good skills to install a prehung door. What can you share so that I might have a fighting chance as I wrestle with this door? Bill F., Greeneville, NC
DEAR BILL: Installing a prehung door is not a job I would entrust to a rookie carpenter. The job is fraught with all sorts of little challenges that are solved with tricks that come with lots of experience. To end up with a door that fits perfectly without rubbing, you need to know some of these tricks. In other words, the salesman either thought you were a seasoned carpenter or he needed to make a sale. No worries though, as I will try to give you as many tips as possible to help you survive this job.
Prehung doors often come from the factory with the jambs a little long. This is done on purpose so you can install the door in places where there will be carpet and not have to cut off the bottom of the new door. The goal is to have about one-half-inch of airspace between the bottom of the door and the top of the carpet or any finished flooring material. The door jambs don't have to touch the subfloor in carpeted situations, but they must be in contact with hardwood flooring, ceramic tile, cork or other finished floors that are typically smooth.
Before the door is installed, make sure the top and bottom of the door is painted. You can just lay the door flat on the ground and open it to check to see if this was done at the factory. It is important to have the top and bottom of doors sealed to prevent warping.
Prehung doors typically come from the factory with a one-eighth-inch gap between the edges of the door and the door jamb. The doors are almost always perfectly square, so the challenge is to square up the jamb within the rough opening so the gap between the door and the jamb stays consistent. The biggest challenge is cutting the lengths of the jambs correctly so the gap at the top of the door is correct. If one leg of the jamb is too long, you will end up with the door rubbing against the top jamb or a horribly large gap between the door and the jamb just above the door knob.
It is really important for the door jambs to be installed plumb. Use a four-foot level to see how plumb the rough opening is that is common to the hinge-side of the door. Use wood shims with the level and tack the shims against the jamb until the level is perfectly plumb. It is best to install shims at the same height as the door hinges.
Position the prehung door into position, slide it up against the shims, and see how things looks. You know you are in great shape if the gap along the hinge side of the door and the top of the door are the consistent one-eighth inch. Don't worry for now about the gap along side the door-knob side of the door. This is the least important jamb.
Use 10-penny finish nails to attach the hinge jamb of the door to the rough jamb. Carefully nail through the jamb and into the shims. Do not drive the nails completely into place. Leave at least one-half inch of the nails exposed in case you need to make adjustments to the length of the door jambs or you have to move the jambs slightly in and out so the door fits perfectly. Once all adjustments are made, all shims are in place and the door fits well, then you can drive the nails home recessing the nail heads with a nail-setting tool.
To really add a professional touch to your installation once complete, you will want to temporarily remove the top hinge from just the door jamb. Doors are heavy and over time the weight of the door can actually pull the jamb away from the finish nails. This will cause the door to rub and not fit well.
If you take a three-inch-long screw and drive it through the jamb into the rough jamb at this upper hinge, the door should stay put for many years. It is important to predrill the hole so you do not split the jamb and create a countersink hole so the head of the screw does not touch the back side of the hinge once the hinge is reinstalled.
Some carpenters just remove one of the regular short hinge screws and replace it with a longer one that will penetrate into the rough jamb. This method will also work.
When shimming the jambs, place the shims at about two-foot intervals and always nail through the jamb at a location where you have installed shims.
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Comments:
brent a varner 05 Dec 2007, 07:15
very good site. very useful info
ken bouchard 03 Feb 2008, 23:03
the prehung doors I bought for my basement have little stips of plastic on
the bottom of the jambs. is it ok to place the jambs right on the
concrete?
tnx,
greg 14 Apr 2008, 18:50
when installing a prehung door, does the door set directly on the subfloor
or do i install it 3/4 of an inch above the subfloor since i am installing
3/4 hardwood flooring?
brian 29 Apr 2008, 08:46
great article except for finish nails. it's not 1970 for goodness sakes;
use 3" drywall screws all the way around, that way for adjustments simply
loosen or tighten the screws. hammering nails is only appropriate for
roofing and framing. also, for finish grade (wood), screw under the
doorstop and then glue the doorstop on, concealing the screws. and lastly,
bill, this isn't rocket science, you'll do great. and greg, you should
wait until your flooring is installed before you install the jambs because
they're technically part of the casing (your job will look VERY diy if you
don't). best of luck
Duane 04 Jun 2008, 19:40
I am taking out 2 windows and putting a 36" door with 2 12" sidelights in
their place. I want to use the existing header. The prblem is I am about
3/4 of an inch short for my rough opening. Should I take the header out and
raise it or cut the flooring witch is 3/4 tongue and grove. then I have to
worry about door clearence over the rug. What would you suggest?
Typical_guy 21 Sep 2008, 19:11
Most of the articals always said "Use 10-penny finish nails to attach the
hinge jamb of the door to the rough jamb"
But really how ? 1. Don't you have to open the door to do this ? 2. Do you think that when you hammer the finish nails nothing is going to move ? 3. I've read one article and I forgot where, but it actually said you shoulr nails through the casing. I'm not so sure now ...
Aaron 22 Sep 2008, 12:00
The builder of my house used the molding to hold the door frames in place.
Since none of the previous owners cared if their internal doors shut, I had
to be the one to fix them. It took me two days to figure it out on my own.
Now I can hang them right in less than a few hours.
This article was good, but don't use nails to hold the frame in. Screws work best and hold better. If the rough opening has more than 1 inch of gap from top to bottom, get a 1" x 4" board to screw to the rough opening. It makes it a lot easier to adjust with shims.
jeremy carlisle 14 Oct 2008, 13:50
what (in your opinion) are the advantages -vs- disadvantages regarding
pre-hung doors??
Steve O 18 Dec 2008, 16:27
I noticed a few dyi's asking about "how high off the floor" should they
hang theIR door? They need to look in to the future, what about the
flooring or tile? Plus, are you going to carpet it or use a throw rug?
Personally, you need to account for all of that and possibly use a door
jamb. Some people don't like dj's, so then your looking at an inch off the
floor so you don't sweep an arc into the carpet every time you open the
door... it's your call.
noah 18 Dec 2008, 21:24
I purchased a bifold door to install it in my basement, I made a doorway
that divides my furnace room from the rest of the basement.
I'm having a very difficult time trying to square up the door jam do you have any helpful hints on how I should do this. When I get the first two sides square by the time I get to leveling and squarering the third side i throw everything out of square. View all comments |
