Interior Door Installation
When I first starting working construction, no procedure reflected the mystical skills of the carpenter more clearly than the installation of an interior door. My door hanging skills never felt quite honed enough until I spent a year on a crew constructing in a condominium complex where we would often install about 10 doors in a day. During this time, I asked a great many questions and did a fair bit of reading on door installation. The following steps are what worked best for me.
In order to measure the rough opening, you will need to remove the existing trim.
Lay the Door Down
Attach the hinges to the jamb, then the door. Double-check that you’re installing the hinges so the door swings correctly.
Screw the Jamb Together
After pre-drilling, secure the head jamb to the hinge-side jamb using 3" #8 wood screws.
Tape Marks the Spot
Apply tape to a long level to mark how far the hinges are positioned from the ground.
Shims Add Strength
Put the end of the level on the ground and install shims where the tape is. This will ensure strength is where you need it – near the hinges.
Is the Floor Flat?
Of course not! A straight piece of wood, the same length as the opening, is used to determine how far off the floor is.
Hinge Side First
Secure the hinge side of the jamb with 3" #8 screws. The screws will be covered by the door stop.
If you need to, use a 3" screw to adjust the head jamb. You just want the gaps on the hinge side of the door and the head jamb side of the door to be equal.
A Strong Latch
When securing the latch side of the jamb, install shims that mirror the hinge side and take extra care to shim the area around the door latch.
Give the Door a Handle
With the door in place, install the latch plate and door hardware.
Cover Your Tracks
Use finishing nails to install the doorstop. It should cover all the screws used to fasten the jamb.
With a sharp utility knife, score all the shims and snap them off. At this point, no shims should protrude beyond the edge of the jamb, and the game is over – this time you won.
To order your new door, first measure the dimensions of the rough opening (RO). This involves removing the casing (trim) so you can measure the height and width of the opening from the framing itself. In addition to the RO, you may need to specify to your supplier either a right- or left-swing door. Stand outside the opening, facing into the room you wish the door to open into. Your swing side is the side with the hinges; the side the door swings into. Doors that are not pre-hung in a frame will often allow you to determine swing at time of assembly.
With the door laying flat on the ground, mount the hinges to the door hinge-side jamb and then to the door. Be careful to ensure the door will swing in the direction you wish it to once mounted. The hinge screws are usually self-drilling and I mark their location with an awl that is slightly off-center so that they pull the hinge into the factory-routed mortise.
Lift the door onto its edge with the hinge-side jamb up. Connect the head jamb to the hinge-side jamb using three #8 wood screws, pre-drilling as required to avoid splitting the jamb. When using MDF jambs, it may be necessary to use brads to avoid splitting. Next, flip the door over and attach the lock-side jamb to the head jamb.
With the door ready to go, it is time to prepare the rough opening. Using a 6″ level, or a smaller level and a straight edge, transfer the location of the hinges to your level with tape measuring up from the floor. The upper hinge will fall just at the top of your level.
Now, hold the level against the hinge-side opening and shim it level against the rough framing. The shims should be placed in line with the tape on your level so that when you install the door, each hinge will be backed by shims against the framing. The shims split easily, so it’s best to secure them with a hand-operated staple gun to prevent the fastener from pulling through.
If the floor spanning the doorway is not level, it will be necessary to cut one side of the jamb to compensate. Use a straight edge the width of the doorway and shim it until level. The distance it has been shimmed off the ground is the distance you need to cut off of the high side. The high side will be the side opposite the side you needed to shim. To make the cut, prop the door on its side and mark your line. I use a circular saw for the cut, but if you doubt the steadiness of your hand then use a handsaw.
Find a buddy, or spouse, to help lift the door into the rough opening. To secure the hinge-side jamb, use three 3″ #8 screws countersunk where they will later be covered by the door stop. Securing the jamb with screws allows for future fine tuning, but a true door master may opt for the use of 15g finish nails for speed. A short straight edge can be handy to help keep the jamb flush with the drywall to provide a level surface to which casing can be neatly secured. At this point, you won’t need your level anymore. With your hinge-jamb secured plumb, you have ensured that the door will not swing open; the rest of your installation is about getting the plumbed door to look right in an opening that is often irregular.
If you were off by a hair when cutting the jamb to accommodate for an uneven floor, you may have to tune that with a screw and shims to dial in the head jamb prior to anchoring the latch-side jamb.
When securing the latch-side jamb, you want to work down from the top, shimming in locations that roughly correspond to the other side. Don’t worry about the jambs being plumb or level; your concern is for the jamb to be on the same plane as the drywall and for the gap between the door and the jamb to be consistent. Before and after anchoring the jamb at each point, close the door to check the gap. If the gap is off, then loosen the screw and adjust the shims as needed. Ensure that you shim behind the door latch as this is a high-impact point.
Now, with the door set, I like to install the latch plate and door hardware. At this point, I will also replace one screw in each hinge on the hinge-side jamb with a 3″ screw going into the framing.
Latch the door and tack the door stop in with finishing nails. I like to start the nails on the ground. You will want to hold the doorstop snug against the door so you will not have any play when the door is closed. Your screw holes should now be hidden from view.
The final step is to snap off the shims. So you don’t end up with a jagged edge proud of the door frame it works best to deeply score both sides of the shims before snapping. In the case of a thick stack of shims, cutting with a small handsaw works best. You are now ready to trim out the door.
When selecting a door for the project I would encourage you to consider spending a little more. Though MDF jambs will look good once installed, they are much less forgiving for the installation. An inexpensive finger-jointed pine jamb will be less prone to splitting during assembly, hold screws better, and take a mortise easier for any required hardware installation. Given the choice I would also pay for a pre-hung door, it easily cuts the time of installation in half.