A few months back, I closed off a hallway and converted it into two storage closets. One near the laundry room became a hall closet and the other end became a linen / bathroom storage closet. I opened up a wall in our bedroom to create a doorway, thus making it a "private" bathroom.

However, due to the spacing of the wall studs, I was left with a very nice door opening with a very unconventional width. Had I been able to, I would have purchased a pre-hung door with it's own frame and been done with it.

So, the purpose of this Instructable is to show you how to modify a pre made door slab that can be purchased at most home improvement stores.

Step 1: MEASURE, MEASURE, MEASURE

Did I mention you want to make measurements?

Door slabs come in standard even widths off the shelf i.e. 24", 28", 30", 32", 34", and 36". Standard height tends to be 80".

The door opening into my bathroom is 26.5"........ so close!

I opted to buy a 30" door to allow myself a little wiggle room.

-A little bit about interior doors-

Generally, an interior door is hollow (sort of). They tend to be made of either Masonite or very thin plywood (supposedly Mahogany) with solid wood vertical edges and particle board tops and bottoms. Inside, they have cardboard glued in a honeycomb/crisscross pattern to provide some rigidity and strength.

This tends to keep the cost of these doors low, but it also makes them a bit difficult to modify.

Now at this point you may be saying "Why don't you buy a solid wood door? Surely it would be easier to modify?" The answer to that of course is yes and no. A solid wood door is very heavy. A solid wood door is also very,very expensive compared to a hollow door.

Step 2: MARK AND CUT

Place painter's tape or masking tape over both sides of the door in the vicinity of where your cut will be. This will prevent the wood from splintering too much while you cut it. Carefully mark the line where you would like to cut.

Measure again, just to be sure. FYI, I cut the door down to 26 1/4"

Cut it. I used a circular saw and went at a reasonable pace to keep it even.

Now you can see what I mean about "sort of" hollow. In order to restore the structural integrity of the door, you will need to fill the gap. Take the discarded piece and remove the surface material from the wooden frame board. I used my old table saw to accomplish this by setting the rip fence in place and cutting away the surface materials.

Step 3: GLUE AND CLAMP

Liberally apply glue to both sides of the frame board and knock it in to place. Clamp the entire length while the glue sets up.

After the glue sets, remove the clamps and cut off the excess glue.

Take the door and test fit it. Satisfied? Good.

Step 4: HINGES AND HARDWARE

At this point, if your door frame is already equipped with hinges, you can cut a hole for the handle and latch, attach the hinges to you door and you are gold.

For me it was a bit more involved, as there had never been a door in this particular spot.

Measure down from the top of the door frame approximately 7". This mark is the top of you hinge. Trace and outline of the hinge onto the frame and use a utility knife to score the line. Next, using a chisel, slowly chip out the area where the hinge attaches. You will want to remove only enough wood for the hinge to be counter sunk into the frame to allow a flush surface. Take you time. Repeat the process for the bottom hinge by measuring up 7" from the floor. For the middle hinge, measure the distance between and divide in half.

Now, in order to line up the hinges on the door, there are two ways I know how to do it.

1. Measure down from the top of the door 7" then add 1/4" (to allow for a small gap between the frame and the door)

2. Place a spacer of some type on the floor and ,placing the door on it, trace the hinge onto the door.

After you have the hinges traced onto the door, repeat the process of chiseling out the outline to allow for the hinge to be countersunk.

Install the door and check for clearance. If it is satisfactory, Measure 36" up from the floor and make a mark on both the door and frame. This will give you the location for the handle, latch and latch plate.

Place the latch plate against the door frame and trace it. I used a paddle bit to remove the wood from where the latch engages. Remove the excess wood with a chisel to allow for flush installation and install latch plate.

The next step is installing the handle and latch. If you have a doorknob install template use it. Otherwise, measure the proper distance from the jamb for the center of the door knob. Cut it out with a hole saw. Use a paddle bit to cut the latch way.

Install the doorknob and function check the door.

Step 5: PAINT, FIT AND FINISH

Use painters caulk or wood filler to fill in any small imperfections on the door and frame. Allow it to fully dry, then apply your finish coat. As I was using white semi gloss, it took me several coats to achieve full coverage. I used a 1/4" fine nap roller for a smooth finish.

Of course, because this door frame was, once again, not a pre-hung door, I will have to add a stop to finish it completely. I used 2" x 4" pine and ripped it down on the table saw. I screwed it onto the frame. Then cleaned sealed everything up with painter's caulk.

After the caulk cured, I painted the frame.

Step 6: FINAL THOUGHTS

I decided to make this Instructable mainly because I couldn't find any sort of clear instructions out there on adding a door after the fact. I hope this helps anyone who may need it.

As always, thanks for reading!