How to Cut a Hollow-Core Door and Get a Perfect Cut Every Time

If you've ever replaced a hollow-core door, or even just shopped for one, you'll know they rarely come in the right size. Sometimes the jamb isn't even straight, and your door either drags on the floor or on the top of the jamb.

In either case, you need to cut the door to fit. But you can't just measure and cut like you can with a solid door. The saw will chip off the finish. The sizing may be uneven. And let's not even talk about all the marks and scratches you can make on the door while you're trying to cut it.

The good news is that with the right preparation and a few carpenters' tricks, you can make the perfect cut quickly and easily.

Prepare and Measure Your Hollow-Core Door

Before you mark or cut anything, make sure the saw won't scratch the door or make it dirty. The quickest way to protect the door is by wrapping the shoe of the saw with masking tape. (You need to do this first, as you'll soon see.)

Measure and mark the door. Then, use a straight edge and a utility knife to score a line all the way across the door. This gives the paint and fibres a 'breaking point', so you get a clean, even cut.

Place your saw blade just below the score line, and mark next to the edge of the saw base to locate a straightedge and guide the cut. Then measure the distance up to this mark and mark it the same distance on the other side of the door. Once you've done that, clamp the straightedge on the door to keep the saw straight while you're cutting.

But don't start cutting yet! Cover the score mark you made earlier with tape all the way around the door to prevent chipping. The underside of the door is less likely to chip because of the direction of the blade, but it's best to be on the safe side.

Making the Cut

Now you can now start cutting. Run the saw slowly along the straightedge to get a nice cut without any chips or marks.

As you'll see, the door is stuffed with foam. You now need to remove some of it to make room for the blocking you'll be adding. The easiest way is to use a wide chisel. If it's tight, you can remove it by gently prying against the inside edge of the door.

Blocking the Door

First, you need to know how wide the opening is in the bottom of the door. Make sure you measure at the outside ends of the door (rather than in the middle), in case the door is slightly warped.

Rip a piece of wood on the table saw according to your measurements, and dry fit the piece into place to check for fit. Once you know it will work, mark it for length and cut it off.

Time to install it into the bottom of the door. Run a bead of glue on the inside edge of each face of the door, and use a hammer to gently tap the blocking into position.

Tap one end in until it is flush with the edges, and then use a brad nailer to hold it in place. Then, continue down the door, tapping and nailing as you go. Just don't push the blocking in too far. (Why brad nails? They're small and leave small holes, so they can be filled and painted easily when you finish the door.)

Well done. You're ready to hang the door. Okay, maybe not quite. You probably need to fill the holes and paint, stain, or otherwise finish it. But you've done the hardest part, so feel free to congratulate yourself for a job well done.