Doorknob and Deadbolt Replacement

Why this matters

Doorknob and deadbolt replacement looks simple but produces a high callback rate because measurement errors at the order-and-buy step cascade into install failures. Backset, bore size, door thickness, latch face dimensions, and strike-plate location all have to match the new hardware to the existing door prep. A wrong order means a return trip; a forced install means a door that no longer latches, a deadbolt that does not throw fully, or a strike plate offset from the new bolt. The professional handles measurement before the trip to the supplier and verifies fit before final installation.

Standard prep dimensions

Most residential doors built since the late 1950s use one of two standard preps:

• 2-3/8 inch backset (most common in homes built since 1980)
• 2-3/4 inch backset (more common in older homes and some commercial-style residential doors)

Backset is measured from the door edge to the center of the bore hole. Hardware is sold for one specific backset or with an adjustable latch that works for both.

Standard bore hole sizes:

• Knob/lever bore: 2-1/8 inch through-bore on the face of the door, 1 inch through-bore on the edge for the latch
• Deadbolt bore: 2-1/8 inch through-bore on the face, 1 inch through-bore on the edge for the bolt

Standard door thickness: 1-3/8 inch (interior), 1-3/4 inch (exterior). Most hardware accommodates both.

Pre-purchase measurement

Before going to the supplier or ordering online:

1. Remove the existing knob or deadbolt so the bore is visible
2. Measure the backset from door edge to bore center
3. Measure the bore hole diameter on the face of the door (2-1/8 is standard; older doors sometimes 1-1/2)
4. Measure the edge bore on the latch face (1 inch is standard)
5. Measure the door thickness at the bore location
6. Measure the latch face plate dimensions (typically 2-1/4 x 1 inch for residential; commercial uses larger)
7. Photograph the existing strike plate and its mortise dimensions on the jamb

Bring the measurements and photos to the supplier. Most failed orders trace to assuming the door uses standard prep when it does not.

Tool list

• Phillips and flat-blade screwdrivers
• 3-inch drywall or wood screws for strike plate reinforcement
• 1 inch chisel for any mortise adjustment
• Drill with 1-inch and 2-1/8 inch hole saws (for new prep work; not for direct replacement)
• Tape measure
• Pencil
• Awl or center punch
• Hammer

Standard knob/lever replacement procedure

1. Remove the existing knob:

   • Locate the retainer screws on the interior rose (usually two screws through the rose into the exterior knob assembly). Some knobs have hidden retainer detents requiring a pinhole pin to release; check the rose for a small hole or slot.
   • Back out the screws, separate the two knob halves, and pull both halves free of the door
   • Remove the two screws holding the latch face plate to the door edge; slide the latch out of the edge bore

2. Inspect the prep. Look at the bore for damage, splintering, or moisture damage. Address any defects before installing new hardware.

3. Install the new latch:

   • Verify the backset matches the existing prep. If the new latch is adjustable, set it to the measured backset.
   • Slide the latch into the edge bore, oriented so the beveled side of the latch faces the door jamb (the bevel allows the door to close smoothly).
   • Secure with the two latch face screws.

4. Install the new knob halves:

   • Insert the exterior knob assembly into the bore from outside, ensuring the spindle and retaining post pass through the latch's actuator hole
   • From inside, align the interior rose over the spindle
   • Drive the retainer screws to draw the two halves together; do not overtighten (which can deform the rose or crack the knob)

5. Test the operation:

   • Turn the knob; the latch should retract fully (3/8 to 1/2 inch) and return to extended under spring pressure
   • Close the door; the latch should engage the strike with a clean click
   • If the latch does not retract fully, the spindle is misaligned or the knob is overtightened
   • If the latch does not engage the strike, the strike position or mortise depth needs adjustment

Standard deadbolt replacement procedure

1. Remove the existing deadbolt:

   • Remove the interior thumbturn screws; separate the two halves
   • Remove the bolt face screws; slide the bolt assembly out of the edge bore

2. Install the new deadbolt:

   • Verify backset
   • Slide the bolt assembly into the edge bore with the bolt fully retracted; orient so the bolt extends parallel to the door face (not skewed)
   • Secure with bolt face screws
   • Insert the exterior cylinder, ensuring the cylinder's tail (or actuator bar) engages the bolt mechanism
   • Install the interior thumbturn over the cylinder tail
   • Drive the retainer screws

3. Test the operation:

   • Throw the bolt with the key; it should extend smoothly to its full extension (typically 1 inch for residential, per ANSI/BHMA Grade 1 requirement)
   • Retract the bolt with the key and the thumbturn; both should operate smoothly
   • Close the door; throw the bolt and verify it engages the strike fully (full extension into the strike box, not just touching)

Strike plate installation

The strike plate is the unsung hero of the install. A correctly installed strike plate transfers load from a kick or pry attempt into the framing behind the jamb. An incorrectly installed strike, or one with too-short screws, fails on the first significant impact.

For both knob and deadbolt strikes:

1. Verify the strike position by closing the door and marking where the latch or bolt contacts the jamb
2. Mortise the jamb if needed so the strike plate sits flush with the jamb surface
3. Drill the strike box hole for the deadbolt to receive the bolt (3/4 inch hole, 1-1/4 inch deep minimum)
4. Install the strike plate with 3-inch screws through the jamb into the framing behind. Strike plate screws that come with hardware are usually 3/4 inch; these are inadequate. Replace with 3-inch screws that bite into the rough framing, transferring load into the structure.

This single upgrade (3-inch screws on every strike plate) does more for residential break-in resistance than any other single change.

Common problems

Latch will not retract fully. Spindle is binding. Loosen the interior rose screws, retighten with the knob in operating position, and re-test. If still binding, the spindle length may not match the door thickness; verify hardware for correct door thickness.

References

• ANSI/BHMA A156.2 - American National Standard for Bored and Preassembled Locks and Latches
• ANSI/BHMA A156.36 - American National Standard for Auxiliary Locks
• ANSI/BHMA A156.40 - American National Standard for Residential Locksets and Auxiliary Locks
• ASTM F476 - Standard Test Methods for Security of Swinging Door Assemblies (strike plate testing)