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

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).