How to Install a Slab Door From Scratch

There are two ways to measure your slab door for cutting: By using the door you’re replacing (or another in your home from the same size frame) or by using the frame itself. 

Replacing a Door

If you still have your old door, you can use it as a template for your new slab. This is the easiest way to hang a slab door, but it isn’t always an option in every situation.

To start, remove hardware and knobs from your existing door. Place the old door directly on top of the new slab door and use clamps to keep it in place. Use a pencil to copy the exact location of the hinges and the door's height, if necessary. 

Using a New Frame 

You'll have to measure yourself if your frame is new or if you don’t have the old door. 

• Measure height: Place the metal part of the measuring tape at the top of your door frame opening and pull it to the ground. If your floor is tile or carpet, stop just ⅛ of an inch above the ground. If you have carpet, leave 3⁄4 inch of room. Use a ruler to ensure a straight line.

• Measure hinges: The top hinge should start 7 inches from the top of the door frame, and the bottom hinge should be 11 inches from the bottom of the frame. Mark these measurements on both your door slab and the frame.

If necessary, use a circular saw to cut your door to height or width. Take extra care to follow a straight line, as uneven cuts will be more noticeable than you think.

Take extra care to determine whether you have a hollow-core door or a solid-core door. Solid-core doors are more durable and easier to cut, while hollow-core doors are slightly less sturdy. Hollow core doors shouldn’t be cut more than an inch, as it can ruin their integrity.

Hinges should be flat with the door, so you’ll need to carve out some wood to make that happen. Using your measurements from step one as a guide, hammer a chisel into the wood to create an even flat area.

Once your mortise is ready, screw your hinge into place using a power drill. Pilot holes may be necessary, depending on your door.

If you notice that your mortise is too shallow, remove the hinge and keep chiseling. If it’s too deep, add a thin strip of plywood or cardboard to level it.

You’re not done yet, there are still more parts of a door to handle—like the knob.

Most doorknobs are 36 inches from the ground, although you can change that depending on you or your door’s height. But, unless you have a good reason to make a change, we recommend installing your doorknob at the standard height.

Place your door knob at this height and mark the opening with a pencil. Cut the opening for the knob itself and the lockset and screw into place.

You’ll also need to install mortises if your frame is new. Follow the same process as step 3 on your door frame.

If your frame already has mortises, it’s time to install your door. Grab a friend or use wood shims or a pry bar to line up the hinges with the mortises on the frame. Make sure the holes in your hinges are lined up precisely with the holes on your frame to avoid accidentally enlarging the hole with a small mistake.

The best way how to hang a door is to start with the top hinge and work your way down.

Now’s the time to test your handiwork. Open and shut the door a few times to ensure it’s level and clears the floor. Take your time to get it right. This is the easiest (and cheapest) time to make any changes to your door, as once you paint and prime it, your door repair cost will be much steeper.