How to Install a Pre-Hung Interior Door

Step-by-step

1. 1

   Check the rough opening

   The opening should be about 2 inches wider and 2 inches taller than the door slab — a 30 in door wants a 32 x 82-1/2 in opening. Measure both diagonals and check the floor across the opening with a level; note which side is high, because you will trim the other jamb leg.

2. 2

   Level the floor reference

   If the floor is out of level, cut the low-side jamb leg's bottom so the head jamb sits level. Trimming the jamb rather than shimming the whole unit keeps the reveal even and stops the door from swinging on its own.

3. 3

   Set the unit in the opening

   Tip the unit into place from the push side with the casing against the wall. Tack one nail through the casing near the top hinge side to hold it, but do not drive it home yet.

4. 4

   Plumb and fasten the hinge jamb

   The hinge jamb is the one that matters. Hold the 6 ft level against it, shim behind each hinge location until it reads plumb in both directions, and drive two fasteners through the jamb and shims at each hinge. Replace one screw per hinge with a 2-1/2 in screw into the framing.

5. 5

   Set the reveal on the latch side

   Close the door and adjust shims behind the latch jamb until the gap between slab and jamb is even top to bottom — about the thickness of a nickel. Shim at the strike plate, top and bottom, then fasten.

6. 6

   Check the swing

   Open the door to several positions and let go. If it drifts open or closed, the hinge jamb is not plumb — back off the shims and correct it now, before the casing goes on.

7. 7

   Score and trim shims, then case the door

   Score shims with a utility knife and snap them flush. Nail the casing to jamb and framing, set the nails, fill, caulk the wall edge and paint.

Safety note: this guide is educational. Always follow local building codes, pull required permits, and hire a licensed pro for structural, electrical, gas or plumbing work when in doubt.