Residential Lock Installation Standard

Purpose

The grade a customer paid for is delivered by the door prep and the strike anchorage, not by what is printed on the box. A Grade 1 deadbolt bolted into a bore drilled off the backset, throwing into a shallow strike pocket held by the 3/4 in screws that came in the bag, gives a door that opens to one shoulder. The lock is not what failed. The install was.

Every acceptance condition below is a dimension, a bolt position or a screw penetration you can read on site, so two technicians hanging the same lockset produce the same door. It also kills the two callbacks this work generates: a bolt that drags after the first cold snap, and a strike screw that spun out and was left spun out.

Scope

New installation and changeout of residential bored (cylindrical) locksets and tubular auxiliary deadbolts on wood and steel-clad doors, including new bore prep, strike prep and commissioning handover.

Excludes rekeying or re-pinning an existing cylinder that stays in the door (see the rekey SOP), mortise locksets and commercial door hardware, electrified hardware (see the electronic access control SOP), and any repair that moves the slab or the frame. A door that will not close square before you start is carpentry, not lock work, and goes back as a separate scope rather than being absorbed by filing the bolt.

Roles and responsibilities

The load-bearing handoff is the measurement block coming back. Without it a callback three months later starts from zero, and the shop eats a second trip to learn a number the first technician already had.

Procedure

Step 1: Measure the door before the box is opened. Record six values on the ticket: door thickness (1-3/8 in or 1-3/4 in on nearly all residential slabs), backset from door edge to bore centre (2-3/8 in or 2-3/4 in), existing cross bore diameter (2-1/8 in standard), edge bore diameter (1 in standard), the gap between door edge and jamb at the lock height (1/8 in is the target and anything over about 1/4 in means the bolt will not seat the same way twice), and what sits behind the jamb at strike height. Acceptance: six numbers written down and the hardware in your hand matching all six. Wrong looks like an adjustable-backset lock out of the box before anyone measured, on a door bored at 2-3/4 in for a trim ring cut at 2-3/8 in. Stop rule: numbers that do not match means re-source the lock rather than enlarge a bore, because an oversized or off-centre cross bore cannot be un-drilled and the recovery is a wrap plate nobody asked for.

Step 2: Confirm the hardware grade against what was sold. ANSI/BHMA A156.2 covers bored locks and latches; A156.36 covers auxiliary deadbolts, and its Grade 1 listing is built around a 1 in minimum bolt throw. Read the certification on the packaging or the BHMA listing for that exact model number, not the marketing panel, because "heavy duty" is not a grade. Acceptance: certified grade on the box equals the grade on the quote, rated throw stated. Wrong looks like a Grade 3 unit substituted into a Grade 2 quote because the supplier was short. Stop rule: any downward substitution is a call to the customer before the hole is cut, with the difference put in cycles and force resistance rather than adjectives, and the choice recorded. Safety glasses go on here: everything after this step makes chips.

Step 3: Bore only after the jig is clamped and the slab is supported. Set the jig to the measured backset, clamp it, and support the slab at both ends so it cannot tip when the hole saw grabs. Bore until the pilot bit just breaks the far face, then finish from the opposite side, which is the only reliable way to keep the exit side from blowing out. On a steel-clad door the saw will grab: two hands, low speed, never freehand. On a pre-1978 painted door, boring and chiselling raises lead-bearing dust, so wet-wipe the shavings rather than dry-sweeping them; EPA's renovation rule at 40 CFR 745 carries a minor-repair exemption for interior work disturbing under 6 square feet per room, which a lock bore sits well under, so the certification requirement generally does not bite while the dust still does. Acceptance: cross bore 2-1/8 in on centre at the measured backset, edge bore 1 in, no tearout either face. Wrong looks like an oval bore or one that wandered off the backset. Stop rule: tearout gets a trim ring quoted before the lock goes on, not discovered by the customer at handover.

Step 4: Mortise the faceplate flush and set the bolt. Chisel the latch or bolt faceplate mortise so the plate sits at or just below the plane of the door edge, within about 1/32 in. Cut away from your hand, with the door edge supported, because a chisel that skates off a painted edge goes into a palm. Install the bolt, then throw it fully with the door standing open and measure the projection past the door edge against the manufacturer's stated throw. Acceptance: the bolt throws its full rated travel by hand with no binding, and the thumbturn returns without spring-back. Wrong looks like a proud faceplate that will rub the strike lip, or a bolt that stops short of its rated throw because the tailpiece is fouling the edge bore. Stop rule: a proud faceplate gets re-mortised now; a short throw gets the bolt pulled and the bore cleared, and neither gets solved by driving the mounting screws harder.

Step 5: Anchor the strike into framing, which is the step that decides the whole install. Mortise the pocket deep enough that the bolt reaches full throw with roughly 1/16 in of clearance beyond it, so it never bottoms on the pocket floor. Use a box or full-lip strike and replace the supplied screws with 3 in screws through the jamb into the trimmer stud. Before driving, probe the void: run one screw in by hand and read where it goes soft, because a jamb shimmed off the stud eats the length you thought you were buying. Set the shop minimum at 1-1/2 in of thread into solid framing, measured rather than assumed - a shop standard, not a code number, and the number that separates a door that resists a kick from one that does not. Acceptance: 1-1/2 in or more into the trimmer, screws seated and not spinning, bolt entering the pocket with the door closed and no contact on the lip. Wrong looks like a head that keeps turning at depth, which means it is crushing jamb or spinning in a void. Stop rule: stop the moment a head spins, pack the void behind the strike with a solid block so the screw clamps wood to wood, step the screw length up until penetration meets the minimum, then re-check alignment, because pulling a shimmed jamb tight moves the strike.

Step 6: Cycle the door closed and read the resistance. With the door shut, throw and retract the bolt ten full cycles, key outside and thumbturn inside. Acceptance: full throw every cycle with the door closed, key turning under light finger pressure only, latch catching on a normal push without lifting or pulling the slab. Wrong looks like a bolt that needs the door pulled toward the jamb, or a key that takes wrist force. Stop rule: never file the bolt or the strike opening to fix a bind. Check the top hinge first, because a sagged slab presents exactly as a strike problem - replace the top hinge's centre screws with 3 in screws into the stud, re-hang and re-test before touching the strike. Still binding after that means the frame is out of square, and it goes back to the customer as carpentry.

Step 7: Hand over at the door, not in the driveway. Test every key in every cylinder you installed, count them aloud with the customer, and show two things: the thumbturn action, and how to confirm a full throw by feeling for the stop rather than looking. State the warranty plainly, register the hardware where the manufacturer conditions coverage on registration, and photograph the thrown bolt in the strike. Acceptance: key count signed for, warranty registered or noted as not required, photos on the ticket. Wrong looks like keys handed over in a bag untested, which is how a mis-cut key becomes a callback at the worst hour. Stop rule: a key that does not run smoothly does not leave the truck - re-cut it, or pull it and record the reduced count.

The record this produces

The measurement block goes on the work order and stays with the job: door thickness, backset, cross bore, edge bore, edge gap, and what the strike screws landed in with the measured penetration. Beside it goes the model, finish and certified grade installed, the measured bolt throw, the cycle test result, the key count signed for, and three photographs - bolt thrown into the strike with the door open, the strike screws seated, and the finished exterior face.

The office reads it twice: at warranty registration, and the day a callback arrives, because a bind appearing in the first cold week is usually a slab that moved and the original edge gap is what proves it. A shop that keeps the block answers that callback with a hinge screw; a shop that does not sends a technician to re-measure a door it already measured.

Worked pass: a deadbolt added to a steel-clad entry door

A 1-3/4 in steel-clad slab, knob lockset in place, customer wants a Grade 2 single-cylinder deadbolt above it. Step 1 records: thickness 1-3/4 in, backset 2-3/8 in to match the knob, no existing deadbolt bore, edge gap 1/8 in, jamb in finger-jointed pine. Step 2 confirms the A156.36 Grade 2 listing and a 1 in throw, matching the quote.

Step 3 bores cleanly, both faces, saw held at low speed with the slab clamped. Step 4 mortises the faceplate to 1/32 in below the edge plane; the bolt throws its full 1 in with the door open.

Step 5 fails. The first 3 in screw spins at about two turns short of seating. Backing it out and probing with the screw shows 3/4 in of jamb stock and then 1-1/4 in of void before solid wood - the rough opening was out of plumb and the jamb was shimmed heavily at that height. That stack is 2 in of nothing structural, so a 3 in screw buries only 1 in into the trimmer, against the shop minimum of 1-1/2 in. It fails, and it fails quietly: the screw feels tight because it is crushing pine, not because it is holding.

Stop rule taken. The technician cuts a solid block to fill the 1-1/4 in void behind the strike so the screw clamps wood to wood instead of drawing the jamb inward, then switches to 3-1/2 in screws. Through 3/4 in of jamb and the 1-1/4 in block, a 3-1/2 in screw leaves 1-1/2 in in the trimmer, which meets the minimum exactly. Because packing the void moved the jamb face about 1/16 in, the strike is re-checked: the bolt now touches the lip on closing, so the pocket is deepened and the strike re-set before step 6.

Step 6 then passes ten closed cycles under light key pressure. Step 7 hands over two tested keys and registers the warranty. Added time for the failure and its fix: roughly 35 minutes on a job budgeted near an hour, so the visit ran about 1.6 times its estimate. That is the honest cost, and it is why the void probe belongs in step 5 rather than in a callback three months out, where the same fix carries a second trip and a customer who has already lost confidence in the lock.

References

• ANSI/BHMA A156.2 (bored and preassembled locks and latches) and A156.36 (auxiliary deadbolts), in the editions BHMA currently publishes; verify a specific model on the BHMA certified product listing rather than on packaging copy
• EPA Renovation, Repair and Painting rule, 40 CFR 745, including the minor-repair exemption for interior work disturbing under 6 square feet per room, which is what puts a lock bore outside the certification requirement while leaving the dust-handling practice in place
• Manufacturer installation template and stated bolt throw for the specific lockset, which governs over any generic dimension here
• See related: Rekey and Lock Change SOP, Identity and Authority Verification Before Any Work SOP