Pro Handyman Blog

A hollow core door is inexpensive, and for good reason. There is a wood perimeter around the door, but the interior is hollow. If you cut one open, you will see what looks like corrugated cardboard. That doesn’t leave me with a strong sense of security. If your opening is too short for your door, you have to cut the hollow core door for height, and reinforce the area you cut.

For example, if you cut the bottom off of the door to the point where the wood perimeter is gone you will be left with an opening at the bottom of the door. You can reinforce this area by using the piece you just cut away from it. From the offcut, peel away the exterior veneer leaving only the wood filler strip. You may need to sand it down somewhat to clean it up.

Also clean up the bottom of the door. You will probably see the corrugated cardboard at the bottom, so you can push that back into the hollow of the door with a chisel. Basically, you want to create a space so that the wood filler piece will sit correctly.

Slather the wood filler piece with wood glue and push it into the opening. It should be a snug fit, but you can use brads or tape to hold it in place until the glue dries.