Rekeying and replacing a lock are two different solutions to the same core problem — controlling who has access to your home. Rekeying is generally faster and cheaper, while a full lock replacement makes sense when the hardware itself is worn, damaged, or simply not up to scratch. Understanding the difference helps you make a smart decision and avoid spending more than you need to.
What Is Rekeying?
Rekeying means changing the internal workings of your existing lock cylinder so that the old keys no longer operate it. A locksmith removes the lock cylinder, replaces the small metal pins (or wafers, depending on the lock type) inside with a different combination, and cuts new keys to match. The lock body, handles, and hardware all stay exactly as they are.
This is the go-to option when:
- You've just moved into a new home and don't know how many copies of the old key exist
- A flatmate has moved out or a relationship has ended
- You've lost a key and want peace of mind
- You want all the locks in your home to work on a single key (keying alike)
Because you're only paying for labour and a small number of new pins, rekeying is significantly more affordable than a full replacement — as a rough guide, expect to pay less than half the cost of fitting a new lock, though prices vary by locksmith and location.
What Is Lock Replacement?
Lock replacement means removing the entire lock mechanism — cylinder, body, handles, strike plate, and all — and fitting a brand-new unit. This is a bigger job but sometimes the right call.
Consider a full replacement when:
- The lock is visibly worn, stiff, or unreliable
- The lock has been damaged in a break-in attempt
- You're upgrading to a higher-security lock (e.g. moving from a basic knob lock to a deadbolt or a Grade 1-rated mortice lock)
- You want to install a smart lock or keypad entry system
- The existing lock brand or type is no longer supported, making rekeying impractical
Lock quality matters for home security. Look for locks that meet recognised standards — in New Zealand, NZS 8101 covers padlocks, and your insurer may specify minimum lock grades for your policy to be valid. Check your policy wording or ask your insurer before choosing a lock.
Key Differences at a Glance
| Feature | Rekeying | Full Replacement |
|---|---|---|
| Cost | Lower | Higher |
| Time to complete | Usually 15–30 min | 30–90 min |
| Hardware changed | Pins/tumblers only | Entire lock unit |
| Improves security grade | No | Yes (if upgrading) |
| Good for worn locks | No | Yes |
| Suits new homeowners | Yes | Sometimes |
| Smart lock upgrade | No | Yes |
What About Master Key Systems?
If you manage a rental property or a small business, a master key system lets one key open multiple locks while individual keys only open their own lock. Setting up or modifying a master key system is a specialist job — a qualified locksmith will assess your needs and design the system properly. Attempting a DIY approach here can compromise the whole system.
For rental properties, the Tenancy Services Healthy Homes standards don't specify lock types, but landlords have a general obligation to provide a property that is secure. Rekeying between tenancies is considered good practice.
Can a Homeowner Rekey or Replace a Lock Themselves?
Unlike electrical or plumbing work, locksmithing is not legally restricted work in New Zealand — there is no licensing requirement equivalent to the Electrical Workers Registration Board or the Plumbers, Gasfitters and Drainlayers Board. In theory, a capable DIYer can replace a lock using hardware from Bunnings or Mitre 10.
However, rekeying requires a rekey kit specific to your lock brand and some mechanical confidence. If done incorrectly, you can end up with a lock that doesn't work at all — potentially leaving your home unsecured. For most homeowners, calling a professional locksmith is the safer, faster option.
Safety note: Never leave your home with a non-functioning lock, even temporarily. If you're mid-job and run into trouble, call a locksmith immediately.
Does Lock Work Require a Building Consent?
Simply rekeying or replacing a like-for-like lock does not require a building consent. However, if you're making structural changes — for example, fitting a new mortice lock that requires cutting into a door frame — check with your local council. Most straightforward lock replacements fall under Schedule 1 exemptions of the Building Act, but it's always worth confirming with your council if you're unsure. See MBIE Building Performance for general guidance.
When to Call a Professional
Call a qualified locksmith when:
- You're locked out of your home
- A lock has been damaged in a break-in
- You want to set up a master key system
- You're installing a high-security lock and want it done correctly
- You're unsure whether rekeying or replacement is the right call
A good locksmith will assess your existing hardware honestly and recommend the most cost-effective solution. You can find qualified local locksmiths on tradedirectory.co.nz.
