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Installation

Installing a door correctly comes down to one thing: getting a square, plumb unit into an opening that may not be square or plumb itself. The door doesn't care about the wall — it only cares about its own frame. This section covers the two main installation approaches and the process for each.

Pre-hung vs. slab​

The first decision is whether you're installing a pre-hung door or a slab door.

A pre-hung door comes as a complete unit: the door slab already hung on hinges within a finished frame, with the hinge and strike mortises already cut. Pre-hung units are the standard choice for new openings or when the existing frame is damaged or out of square. They take more time to install but eliminate most of the precision fitting work.

A slab door is the door panel alone, with no frame. Slab installations reuse the existing frame and are faster when the frame is in good condition and square. The tradeoff is that all mortising — hinges, lockset, strike plate — must be done in the field.

tip

If you're replacing a door and the existing frame is solid and square, a slab is usually the faster and less disruptive choice. If anything about the frame is damaged, rotted, or significantly out of square, replace it with a pre-hung unit.

Tools & materials​

Before starting, gather the following:

  • Tape measure and combination square
  • 4-foot level
  • Hammer and chisel (for mortising)
  • Drill and bits (including a spade bit for lockset bore)
  • Hole saw kit (for lockset, if not pre-bored)
  • Utility knife
  • Handsaw or circular saw (for trimming, if needed)
  • Shims (cedar shims are standard)
  • 3-inch wood screws (for hinge and strike reinforcement)
  • 16d casing nails or finish nailer
  • Pry bar (for pre-hung installations)

Installing a pre-hung door​

1. Prepare the rough opening​

The rough opening should be the door size plus approximately 2 inches in both width and height — enough to fit the frame plus shims on each side. Verify the rough opening is within ¼ inch of square by measuring diagonally corner to corner in both directions. If the measurements differ by more than ¼ inch, the opening needs correction before proceeding.

2. Set the unit in the opening​

With a helper, lift the pre-hung unit into the rough opening from the exterior side (for exterior doors) or from the side where the casing will show. Center it in the opening and tack it temporarily in place with one nail through the casing near the top hinge.

3. Shim and plumb the hinge side​

The hinge side is set first. Place shim pairs — two shims driven from opposite sides until snug — behind each hinge location. Check the hinge-side jamb for plumb with your level. Adjust shims until the jamb is perfectly plumb, then nail through the jamb and shims into the rough framing with casing nails. Drive one nail at each shim location, leaving nail heads slightly proud until the fit is confirmed.

4. Check the head jamb for level​

With the hinge side plumb, check the head jamb for level. If it isn't level, the latch-side jamb will need shimming to compensate. A level head jamb is less critical than a plumb hinge jamb, but significant deviation will show in the reveal — the gap between door edge and jamb — once the door is hung.

5. Shim the latch side​

Shim the latch side at the strike location and at the top and bottom of the jamb. The goal is a consistent reveal of approximately ⅛ inch on the latch side and head. Hang the door and check the reveal before driving any additional nails.

6. Hang the door and check operation​

If the door wasn't shipped in the frame, hang it now by setting the hinge leaves and tapping the hinge pins in from the top. Open and close the door slowly. It should swing freely with no binding and latch without lifting or forcing. Check the reveal on all three sides — hinge, latch, and head. It should be consistent, ideally between ⅛ and 3/16 of an inch.

note

Imperfect reveal or binding at this stage is normal and fixable. See Fit & Adjustment before making any irreversible cuts or modifications.

7. Secure and finish​

Once the fit is confirmed, drive all nails home and set them. Score the shims with a utility knife and snap them flush with the framing. Install the lockset and strike plate, then test the latch. Apply casing on both sides to cover the gap between frame and rough opening, nailing into both the jamb and the framing.

Installing a slab door​

1. Assess the existing frame​

Before ordering a slab, measure the existing door and verify the frame is square and in good condition. Check the hinge jamb for plumb and the head jamb for level. If either is significantly off, a slab installation will transfer those problems directly to the new door.

Measure the existing door's height, width, and thickness. The replacement slab should match exactly, or be slightly oversized if fitting and trimming will be needed.

2. Transfer hinge locations​

Hold the new slab against the existing door face to face, aligned at the top and hinge side, and transfer the hinge locations with a pencil. Use a combination square to extend the marks across the door edge.

3. Mortise the hinges​

Set the hinge leaf on the door edge, centered on the mark, and trace around it with a utility knife. Chisel the mortise to the depth of the hinge leaf — typically ⅛ inch — so the leaf sits perfectly flush. Test-fit the hinge before moving on.

Repeat for all hinge locations on the door edge. The frame mortises should already exist from the previous door; if they need adjustment, chisel carefully to avoid removing too much material.

4. Bore the lockset​

If the door isn't pre-bored, mark the lockset location at standard height — typically 36 inches from the floor to the centerline of the knob or lever. Use a hole saw to bore the face hole (typically 2⅛ inches in diameter) and a spade bit for the latch bore through the door edge. Follow the lockset manufacturer's template exactly.

5. Hang and check​

Hang the door, tap the hinge pins in, and check operation and reveal as described in the pre-hung process above. A slab going into a good existing frame should need minimal adjustment.

A note on door height and floor clearance​

Standard door height is 80 inches (6 feet 8 inches), though 84- and 96-inch doors are increasingly common in newer construction. The bottom of the door should clear the floor finish by approximately ¾ inch for carpet and ½ inch or less for hard flooring. If the clearance is wrong, the door will need to be trimmed from the bottom — covered in Fit & Adjustment.

Next: Fit & adjustment​

Installation gets the door in the opening. Fit & adjustment is where the real work happens — dialing in the reveal, fixing binding, correcting a dragging bottom, and everything else that stands between a hung door and a door that works properly.