Rekey vs Replace vs Master Key Decision Matrix

Why this matters

The three most common residential and small-commercial locksmith calls converge on the same question: rekey what's there, replace with new hardware, or upgrade to a keyed-alike or master system. Each answer drives a different parts list, a different labor envelope, and a different long-term tenant relationship. Rekey is fast and cheap but inherits the existing hardware grade. Replace gives you a fresh start but creates twice the cost. Master key opens architectural options for landlords and commercial property managers but multiplies pinning complexity and creates security tradeoffs. This matrix gives a field rule that lets a tech in the truck reach a defensible recommendation before walking to the front door.

Symptom presentation - what triggers the three calls

• Move-in / tenant turnover: customer wants the old keys made useless. Default answer is rekey - hardware is presumed serviceable until inspected.
• Lost keys / break-in / safety event: customer wants confidence that no copies exist. Rekey serves; replacement may be requested for emotional reset; master systems are unnecessary.
• Worn hardware: lock binding, latch sluggish, deadbolt sticking; rekey will not fix the mechanical condition. Replace.
• Multiple-door simplification: customer wants one key to operate all exterior doors. Keyed-alike (residential) or master (commercial).
• Property manager onboarding new building: master key system from day one, with restricted keyway and key control records.

Quick checks at the door

Before quoting, do the four-point inspection on each lock:

1. Grade stamp: ANSI/BHMA grade marking on the lock case. Grade 1 commercial, Grade 2 light commercial/heavy residential, Grade 3 residential basic.
2. Mechanical condition: turn the key in both directions; key withdrawal smooth; deadbolt throws fully (1 in standard, no binding).
3. Door condition: latch hits the strike cleanly; gaps under 1/8 in; strike plate held with 3 in screws into the framing.
4. Cylinder type: standard 5-pin or 6-pin, high-security restricted, smart lock with mechanical override.

A Grade 3 builder-installed lock with a sticky cylinder is not rekey-eligible - rekeying it puts new pins into a worn body and the customer is back in 18 months. Replace.

Isolation tree

1. Lock is mechanically failing (binding, sluggish, deadbolt incomplete)? Yes → replace; rekey will not fix mechanics. No → continue.
2. Lock is below ANSI/BHMA Grade 2 and the property is the customer's primary residence? Yes → recommend replace with Grade 2 minimum; offer rekey as the budget option with disclosure that the existing lock is short-life. No → continue.
3. Customer needs guaranteed no-outstanding-keys (lost key, terminated tenant, break-in)? Yes → rekey is sufficient if hardware is serviceable; replace if customer requests emotional reset or hardware is non-serviceable. No → continue.
4. Multiple doors and customer wants one key for all? Yes (residential, 2 to 5 doors) → keyed-alike rekey to a shared bitting; verify all lock brands are compatible with one keyway. No → continue.
5. Commercial property with multiple users and stratified access (owner, manager, staff, cleaning)? Yes → master key system; specify levels, restricted keyway, key-control records. No → continue.
6. High-security requirement (medical office controlled substances, financial services, federal contractor)? Yes → high-security cylinder with patented keyway (Medeco, Mul-T-Lock, Abloy class); not a standard master. No → continue.
7. Smart lock requested or in place? Yes → install or rekey mechanical override per manufacturer (most smart locks accept standard pinning); discuss network and credential management separately.

Confirming the diagnosis - the customer conversation

Three openers depending on which branch the tree landed on:

• Rekey path: "Your existing locks are mechanically sound and Grade 2 or better. I'll rekey all [N] doors to a single new key, which makes any lost or terminated keys non-functional. Cost is [parts and labor scope]; turnaround [time]."
• Replace path: "Your existing locks are [Grade 3 / mechanically failing / non-serviceable]. Rekeying buys 6 to 18 months at best; the cost-effective path is to replace with [Grade 2 cylinder lockset]. I'll match the trim and bore size so no carpentry is required."
• Master path: "For a property with [N] users at [levels of access], a master system gives each user a key that opens only the doors they need. The master opens all doors. Restricted keyway means keys cannot be duplicated at a hardware store. Initial setup is [scope]; ongoing key-control records are required."

Confirming - master key system design rules

A master key system collapses on three predictable failures. Design around them:

1. Maximum changes (MAC): a 5-pin master system has a finite number of unique change keys (typically 30 to 60 per master) before keying duplications and security cross-cuts force a 6-pin or 7-pin upgrade. Plan the system at 60% of MAC on day one to leave room for tenant turnover.
2. Restricted keyway: without a restricted (patented) keyway, the operator master is duplicate-able at any hardware store; the system is compromised the day the first key walks. Always specify a restricted keyway for commercial master systems.
3. Key control records: written log of which key is held by whom, signed receipts on issue, and a returned-key procedure on termination. Without records, "we don't know how many copies are out" is the response after any incident.

Confirming - parts on the truck

The 5 SKUs that cover 80% of residential and small-commercial rekey/replace calls:

• Grade 2 deadbolt in stocked finishes (satin nickel, polished brass, oil-rubbed bronze) - 4 to 6 per stocked finish.
• Grade 2 keyed entry lever or knob, matching finishes.
• Pin kit (Schlage C, Kwikset KW1, Weiser WR3, and one or two restricted keyway pin kits if the route has master commercial accounts).
• Strike-plate upgrade kit (4 in screws, reinforced strike).
• High-security deadbolt as a stocked upsell for safety-conscious residential calls.

If the truck doesn't stock the keyway the customer's existing lock uses, the rekey becomes a parts delay or a forced replacement. Stock the keyway diversity that matches the route.

Remediation execution standards

The recommendation is only half the job. These are the execution standards that decide whether the customer calls back in a year for more work or for a warranty complaint.

Rekey.

1. Count and verify every cylinder before you start, including the ones the customer forgot (back door, garage service door, gate, shed, mailbox, padlocks). A rekey that misses one door has not accomplished the customer's actual goal.
2. Clean and inspect each plug as you pin it. Replace worn or mushroomed pins and any spring that has taken a set. Reusing tired springs is where the intermittent stuck key comes from.
3. Cut new keys on a calibrated machine and deburr them. Hand the customer keys that feel new, not keys that drag.
4. Test each cylinder in the lock, in the door, at least three full cycles from both sides, with the door closed. A cylinder that turns on the bench and binds in the door is a door problem you now own.
5. Collect and account for the old keys. Tell the customer explicitly that any key not returned is now useless, which is the point of the visit.

Replace.

1. Match backset, bore diameter, door thickness, and handing before anything comes off. Confirm the existing prep rather than assuming a standard.
2. Upgrade the strike while the door is open: reinforced strike, screws long enough to reach the framing behind the jamb. This is the cheapest real security improvement on any residential door and it takes minutes when you are already there.
3. Set the deadbolt so it throws fully with the door closed, with no binding and no lift required. Adjust the strike, not the customer's habits.
4. Key the new hardware alike across the opening set unless the customer asked otherwise, and confirm that choice out loud before you pin.
5. Leave the old hardware with the customer or dispose of it on request, and note which you did.

Master system.

1. Build the bitting schedule on paper before you touch a cylinder. Assign every door a position in the system, including doors not yet cut over.
2. Pin, cut, and test one level at a time. Verify that each change key opens exactly the doors it should and nothing else, and that the master opens everything. Test the negative cases; that is where cross-keying errors surface.
3. Stamp or label cores against the schedule, never against a person's name.
4. Deliver the key-control package: the bitting record, the issue log, signed receipts, and a written termination procedure. Walk the property manager through it in person.
5. Retain your own copy of the system record in a secured file. When the manager turns over, you are the continuity.

On every job, document what was done per door, photograph the finished hardware, note anything you deferred and why, and put warranty terms in writing. The deferred item you documented is the upsell you close next visit; the one you only mentioned verbally is the complaint you get instead.

References

• ANSI/BHMA A156.5, Auxiliary Locks (deadbolt grading standard).
• ANSI/BHMA A156.13, Mortise Locks (commercial mortise locks).
• ANSI/BHMA A156.115, Hardware Preparation in Steel Doors and Frames (replacement compatibility).
• ALOA Master Keying Standard (industry consensus on master system design and key control).
• UL 437, Standard for Key Locks (high-security lock certification baseline).