How to Trim the Bottom of a Door

Do you know the difference between “hanging a door” and “installing a door?” Though these terms often are used interchangeably, today, there is a distinction. Before the rise of prehung doors, carpenters used to install the door frame, and then “hang” the door within the frame. The skill set to hang a door included, trimming and beveling the door, mortising hinges, and installing passage sets, lock sets, and deadbolts, among other things. Today, it’s more common to just “install” prehung doors. Still, there are lots of reasons why you may need to trim a door, reasons that often pop up during remodeling projects.

The necessity of trimming a door goes along with remodeling projects where the floor rises because of added carpeting, new tile, or extra layers of subflooring (or in my case, whenever my penchant for area rugs gets the best of me). As someone who has remodeled other people’s homes as well as my own, I have tackled this project over and over. To trim a door problem-free, I call on the same skills I use for other finish-carpentry projects, such as built-ins, wainscoting, and countertops.

Although you can use straight-edge guides, track saws, and zero-clearance throat plates to cut finished work, I use a 4-ft. level clamped to the door and a thin-kerf blade in my circular saw for a task like this. I also use a utility knife to score the door and some masking tape to protect the surface of the door. Finally, I need a gauge block, which I usually make from a piece of thin plywood. Here’s a step-by-step look at my process for trimming a door bottom:

Step 1: Mark the door for the cut. At the bottom of the door, I put a piece of tape on both the hinge side and the strike side (the side with no hinges). I place the rug against the closed door and mark both pieces of tape 1/4 in. above the rug using a scribing compass. If you were preparing to install tile or another type of flooring, you could lay down a piece of the material in front of the door to make your marks. If it is tile, remember to account for the thickness of the thinset.

Step 2: Draw the cutline. With the door taken off of the hinges and set on sawhorses, I connect the two marks with tape, then use the level to draw a straight line between them.

	Step 4: Make a gauge block. This scrap of wood is cut at the exact distance from the edge of the blade to the edge of the saw’s baseplate.
	Step 5: Use the gauge block to set the level back from the cutline. The block should just cover the scored line. The level is secured to the door with two clamps.

Step 6: Tape the door, not the saw. To avoid marring the door, I put down two layers of tape next to the level. I tape the work because it’s faster than taping the bottom of the saw and because it’s easier to clean up.
Step 7: Make the cut. I set the cutting depth so that the blade just cuts through the door and focus on the baseplate when making the cut. The baseplate edge stays in contact with the level while the bottom runs flat on the door. To prevent the blade guard from dragging on the door, I hold it retracted during the cut.

	Step 8: Ease the edge. To prevent the bottom of the door from splintering over time, I ease the edge using a small block plane. Some 80-grit sandpaper wrapped around a sanding block works just as well.
	Step 9: The payoff. Hang the door back on the hinges, The trimmed door should clear the rug easily and operate smoothly.

The right blade for a clean cut

For general finish work, I use a sharp thin-kerf blade in my circular saw. It removes less material, so it’s easier on the saw. I’ve had good results with Freud’s Diablo 24-tooth framing blade (D0724X), which costs about $10 (www.freudtools.com). Although you can buy pricier finish-cutting blades with more carbide-tipped teeth, this framing blade delivers smooth cuts and doesn’t overwork the saw.

Photo: Courtesy of Freud

Photos by: Charles Bickford, except where noted