When trimming interior door to fit, don’t cut too much

Q: I am replacing an interior door that needs to be cut down. Either I bought the wrong size door or the opening for it is not a standard size. The door is hollow and I need to cut it down by about an inch in height and one-quarter in width. What is the best way to do this, and does it severely weaken the door?

A: If you bought your door from a home center, chances are you will have to trim it for width. You say that you need to cut 1 inch off the height? That sounds excessive.

My guess is that the opening may not be standard or maybe the height of your flooring is taller than most.

Anyway, cutting the door is not a big deal; you just can’t cut too much off of it.

Let’s face it, a hollow core door is a cheap door. If you were to peel the veneer off of one, you would see a wood frame around the perimeter of the door (there is some additional wood around the hole for the doorknob). To support the veneer sides inside of the wood perimeter are cardboard supports that wander throughout the door. This explains why hollow core doors are so light and inexpensive.

Needless to say, since you are working with only one frame of wood to trim, you have to be careful about how much to cut. The amount you need to cut from your door is fine with a few caveats.

When cutting the width of the door, cut it on the hinge side. If you cut material away from the doorknob side, it will change the backset (the distance from the doorknob to the edge). If that happens, the doorknob latch will be exposed, it won’t fit correctly, and then you’ll have to buy a new door. So cut your sliver from the hinge side, but make it clean, square and thin.

A table saw is ideal for this, but a circular saw will also work. If you’re using a circular saw, clamp the door to the work surface and make sure the blade is set to 90 degrees. If you have even the slightest bevel on the hinge side, you will put stress on the hinges when you mount the door. In turn, that puts stress on the now-thinned-out frame and you will have problems.

Use a straightedge and clamp it to the door. Finally, run a piece of tape along the area where the blade will cut. This will help prevent tear-out as the blade comes up through the door.

If you take too much material from the hinge side, the screws that secure the hinge to the door won’t have enough wood to bite into. That could take away the needed support for the weight of the door.

The long and short of it is that if you need to cut a good amount of wood from the width of the door, you may need to order a custom-size door. Expect to pay double and wait seven to 10 days to get it.

Cutting the height of the door is not nearly as risky. Generally, a door gets cut on the bottom due to the tall carpeting that may rub on it. But take a few measurements before you cut. If your door has a pre-cut hole for the knob, make sure it is going to line up with the strike plate on the jamb. If it doesn’t, you may consider taking a little off the top as well.

You can cut the height of the door in the same manner as the width described above.

If you have a significant amount to cut, you are going to cut beyond the frame and into the hollow of the door. This is fine, but you should replace the frame piece back into the hollow to strengthen it. You will have to chop the veneer from both sides of the frame to get it to fit back into the hollow.

Use a chisel and a hammer and cut the veneer away. You may have to sand the frame piece to get it to slide smoothly back into place. Slather the frame piece with wood glue and slide it into the hollow area and wipe away the excess glue before it dries. Then clamp it together until it dries.

The only thing left now is to hang the door. Line up the hinges and cut out the mortises for the hinges (the hinges lay in the mortise so the entire edge is flat). Mark lines for the hinges, and chop out the area using the hammer and chisel (or you can buy a template and bit).

Pre-drill holes for the hinge screws and screw the hinges to the door and then the jamb. Remember, don’t crank the screws completely tight until you are happy with the overall fit of the door.

Mike Klimek is a licensed contractor and owner of Las Vegas Handyman. Questions may be sent by email to handymanoflasvegas@msn.com. Or, mail to 4710 W. Dewey Drive, No. 100, Las Vegas, NV 89118. His web address is www.handymanoflasvegas.com.