What You Need to Know Before You Change Your Door Lock
Changing a door lock is one of the most effective security steps you can take - and one of the most misunderstood. You should rekey when the lock is sound but old keys need to stop working; replace when the lock is worn, damaged, or below British Standard. Key trigger points are moving into a new home, losing keys, a break-in, or a change of tenancy. Costs start from around £55 for a rekey and £69 for a lock change in labour (ex VAT), with the lock hardware on top.
Why People Change Their Door Locks
Security Reasons
The most common motivation is security. You should consider changing your lock when:
- Keys have been lost or stolen
- You have moved into a new home and do not know who holds copies of the existing keys
- A tenant or flatmate has vacated - even if they returned the keys, copies may exist
- There has been a break-in or attempted break-in - even if the lock itself was not forced
- The existing lock is old, worn, or does not meet current British Standards
Aesthetic and Functional Reasons
A new lock can refresh the look of a front door, particularly if you are updating door furniture. Locks come in a range of finishes, from brushed chrome to antique brass.
Locks also wear out over time. If your key sticks, the lock feels stiff, or the bolt does not engage cleanly, replacing the mechanism restores smooth, reliable operation. For specific guidance on Yale locks, our article on changing a Yale lock explains when and how to replace them.
Rekey vs Replace: Which Do You Need?
This is the most important decision. Understanding the difference saves you money and avoids unnecessary work.
What Is Rekeying?
Rekeying changes the internal pin configuration of your existing cylinder so that old keys no longer work and a new key is issued. The lock body, door hardware, and fitting all stay in place. It is faster, cheaper, and causes zero damage to your door.
Choose rekeying when:
- The lock is in good working order but you want to cancel old keys
- You are moving into a new home and the existing locks meet BS 3621
- A tenancy has ended and you want to prevent key re-use
- You want multiple locks on the property to operate from one key
City Locksmith London offers a lock re-key service from £55 labour (ex VAT).
What Is Full Lock Replacement?
Replacement removes the entire lock mechanism and fits a new one. This is the right choice when the lock itself is the problem.
Choose full replacement when:
- The lock is visibly worn, stiff, or damaged
- The lock does not carry anti-snap, anti-pick, or anti-drill protection
- The lock fails British Standard BS 3621 or your insurer’s requirements
- There has been a break-in and the mechanism may be compromised
- You are upgrading to a multi-point system or smart lock
Our lock change service starts from £69 in labour (ex VAT), plus the cost of the new lock hardware.
When Should You Change Your Locks?
Moving Into a New Home
This is the single most important time to change or rekey your locks. Previous owners may have given keys to estate agents, relatives, cleaners, builders, and neighbours - none of whom you know. A fast rekey or replacement on moving day guarantees that only you control access.
Tip: If the existing locks are BS 3621-rated and in good condition, rekeying is all you need. If they are older or lack the kite mark, replace them with compliant cylinders at the same time.
After a Break-In
Replace your locks immediately after a break-in, even if the intruder entered another way. Lock integrity may have been tested or damaged during the attempt. Upgrading to an anti-snap, anti-pick cylinder also hardens the property against a repeat visit. See our break-in repair service for same-day response across London.
Lost or Stolen Keys
A lost key is a lost lock. You cannot know where the key is or who has found it. Rekeying is usually sufficient here - there is no need to buy new hardware if the lock itself is sound.
After a Tenancy Ends
As a landlord, you should rekey between every tenancy. Tenants may have had keys cut without your knowledge. A rekey between occupants is a small cost with significant peace of mind.
Ageing or Substandard Locks
Consider replacement if locks are more than 10 to 15 years old, show signs of corrosion or stiffness, or do not carry a BS 3621 or TS007 three-star marking. Insurers may refuse claims if the lock at the point of entry was non-compliant.
Can a Tenant Change the Locks?
In England and Wales, most tenancy agreements require written landlord permission before a tenant makes any alteration - including changing a lock. Acting without permission can constitute a breach of contract.
However, there are situations where a tenant has a legitimate reason to act quickly:
- Lost or stolen keys - where the landlord cannot arrange a prompt replacement
- After a break-in - immediate security is required
- Genuine safety concerns - such as domestic abuse situations where the risk outweighs the procedural requirement
If you do change a lock as a tenant, best practice is to:
- Notify your landlord in writing as soon as practicable
- Provide the landlord with a copy of the new key
- Keep the original lock so it can be reinstated when you leave
A landlord cannot change the locks to exclude a tenant - doing so without a court order constitutes illegal eviction, which is a criminal offence in the UK.
Key Factors to Consider Before Changing Your Lock
Door Material and Compatibility
Your replacement lock must match your door. uPVC doors take a euro cylinder (measure the existing one before ordering - total length and the split between inside and outside). Timber doors may use a British Standard five-lever mortice. Composite and aluminium doors vary by manufacturer. Door thickness matters too - some locks need adaptor hardware for non-standard profiles.
Security Rating
For all external doors, look for one of the following:
| Standard | What It Means |
|---|---|
| BS 3621 | British Standard deadlock - the insurance baseline |
| TS007 3-star | Combined cylinder + escutcheon rating - highest tested protection |
| Sold Secure Diamond | Third-party tested against attack |
Anti-snap cylinders are essential for uPVC doors fitted with euro cylinders - snapping is the most common forced-entry technique in the UK. See our guide on high-security locks for a full breakdown of ratings.
DIY or Professional?
Swapping a euro cylinder on a uPVC door is within reach of a careful DIYer if the old cylinder is accessible and undamaged. However, fitting a mortice lock, adjusting a multi-point mechanism, or installing a smart lock correctly requires precise alignment. Errors cause misalignment, premature wear, or - worse - a door that can be defeated with finger pressure. Our residential locksmith service covers all door and lock types across London.
Budget
A realistic breakdown of typical costs:
| Job | City Locksmith London (labour, ex VAT) | UK market range (incl. parts) |
|---|---|---|
| Lock re-key | From £55 | Typically £45-£65 per lock |
| Lock change (labour) | From £69 | Around £100-£150 incl. parts |
| Fresh lock installation | From £89/hr | Around £80-£150 incl. parts |
| Repair / fix mechanism | From £99 | Around £99-£200 |
| Smart lock fitting | From £129/hr | Around £250-£500 incl. hardware |
For a full breakdown, see our locksmith price list. There are no call-out fees and quotes are free.
Insurance Requirements
Most UK home insurers require BS 3621 five-lever mortice locks on timber doors and a TS007 three-star cylinder on uPVC doors. Check your policy schedule before buying a replacement - fitting a non-compliant lock and then being burgled may invalidate your claim.
Anti-Snap, Anti-Pick, Anti-Drill: What You Need
Anti-Snap Protection
Cylinder snapping takes under 30 seconds with basic tools and is the most common break-in method used against uPVC doors. An anti-snap cylinder sacrifices a designed break point outside the security zone, leaving the inner mechanism intact and the door secure. This should be considered essential on any uPVC or composite door.
Anti-Pick and Anti-Drill
Quality cylinders include hardened steel anti-drill pins and specially toleranced tumblers that defeat picking. Both features are standard on most BS 3621 and TS007-rated cylinders. Look for them alongside anti-snap on any front or back door.
Key Control
Patented key systems restrict duplication to authorised dealers. This is valuable for landlords, HMO operators, and businesses where key management matters. Ask your locksmith about restricted key systems when having a full replacement done.
Smart Locks
Smart locks replace a cylinder or deadbolt with a device operated by code, phone app, fingerprint, or fob. They suit households that manage frequent visitor access or want remote locking capability. For a full review of tested models, see our guide to smart locks for UK homes. Professional fitting ensures correct alignment and, on battery-powered models, that a physical override key is accessible.
Choosing the Right Lock for Your Door
uPVC and Composite Doors
These use a multi-point locking mechanism operated by a euro cylinder. The cylinder is the replaceable security component. Measure yours before buying a replacement - total length and the split (e.g. 35/45). Fit an anti-snap, BS-rated cylinder. For a step-by-step guide to replacing the cylinder yourself, see how to replace a barrel lock in a uPVC door.
Timber Doors
Traditional timber front doors typically use a BS 3621 five-lever mortice sashlock or deadlock as the main security lock, combined with a night latch (Yale-style) for convenience. The mortice lock is the insurance-required component. For advice on the full range, see best front door locks for UK homes.
Aluminium Doors
Aluminium-framed doors vary significantly between manufacturers. Some use euro cylinders; others use proprietary mechanisms. Match the lock to the door specification or call a locksmith to assess before ordering parts.
Get Professional Help Across London
City Locksmith London is fully insured with DBS-checked engineers, available 24/7, and responds across Greater London in under 25 minutes. There are no call-out fees and all quotes are free.
- Lock change service - from £69 labour ex VAT
- Full lock installation - from £89/hr ex VAT
- Residential locksmith London - all door and lock types
- Locksmith price list - transparent pricing with no surprises
- Need advice? Contact a locksmith - no obligation