Top Reasons to Consider Changing the Locks on Your Doors

Changing the locks on your home is one of the most direct improvements you can make to your security — and one of the most frequently postponed. This article is for homeowners, tenants and landlords who want to understand when lock changing is not just sensible but necessary, what to look for in a replacement lock, and the insurance implications of BS3621, the British Standard underpinning most home insurance lock requirements.

Moving Into a New Home

This is the most overlooked reason to change locks, and one of the most important. When you move into a property, you have no reliable way of knowing how many copies of the existing keys exist. Previous occupants may have given copies to neighbours, friends, family members, tradespeople, or anyone else who needed access over the years. Estate agents often hold a key during the sales process, and their staff, contractors, and anyone who attended viewings may have had access.

The appropriate response is to change all external door cylinders before or on the day you collect the keys. A cylinder replacement on a standard Yale or euro-cylinder lock runs from £40 to £80 per lock including parts and labour. For a three-bedroom semi-detached with front and back door, budget around £100 to £160 for the job. This is not a theoretical risk — it is a documented source of residential break-ins where a key rather than forced entry is used.

After a Break-In or Attempted Burglary

If your property has been burgled, the police will advise you to review your security immediately. Replace any lock that was damaged, bypassed or left vulnerable during the incident. Do not simply re-fit the existing cylinder if it has been forced or drilled. If your locks do not currently meet BS3621, a post-break-in upgrade is the right moment to address that, particularly given the insurance implications covered later in this article.

After an attempted break-in, even one where entry was not achieved, carry out the same review. A failed attempt often means the attacker identified something about the lock or door worth returning to.

Lost or Stolen Keys

If your keys have been misplaced within your home and you are confident no third party has them, rekeying the existing cylinder is a proportionate and cost-effective response. If there is any possibility the keys are in the hands of someone who knows your address, change the locks that day. This applies to keys stolen as part of a theft, keys lost near your home, and keys that have been in the possession of someone you no longer trust with access. The cost of a cylinder change is significantly less than the cost of dealing with an entry made with your own key.

End of Tenancy and Change of Occupancy

Landlords have a practical interest in changing locks at the end of each tenancy. Outgoing tenants should return all keys, but compliance is inconsistent, and whether keys have been copied during the tenancy cannot be verified. Not changing locks between tenancies can also create liability issues if a subsequent break-in occurs and it can be argued the change would have been a reasonable precaution.

For tenants, there is a separate consideration: if you have lost a set of keys during your tenancy, you are likely contractually required to inform your landlord. Whether a lock change follows is a matter for landlord and tenant to agree, but ignoring the situation is rarely in your interest.

Old, Worn or Inadequate Locks

Locks deteriorate. A cylinder that has seen ten years of daily use will be stiffer, less consistent and more vulnerable than a new one, even if it appears to be functioning. The pins and springs inside wear down with repeated operation. A worn cylinder is easier to pick and offers less resistance to attack than a new one.

Beyond wear, many older properties have locks that were never adequate. A basic rim latch provides very little security against a determined entry attempt. A standard five-lever mortice deadlock meeting BS3621 is a far more secure replacement. If your locks are more than ten years old or are clearly old builder-grade hardware, the investment in a replacement is small relative to what it protects.

End of a Relationship or Change in Trusted Contacts

If you have ended a relationship where the other person had a key, or have had a significant falling-out with someone who holds a key to your property, change the locks. It does not matter whether you believe the other person would actually use the key inappropriately — what matters is that you no longer control who can enter your home. A cylinder change costs between £40 and £80 per lock and is straightforward to arrange.

This applies equally to tradespeople. If a builder, cleaner or carer held a key and that arrangement has ended, asking for the key back is sensible but not sufficient — keys can be copied. A cylinder change is the only way to be certain.

Upgrading for Insurance and Higher Security

Many home insurance policies require door locks to meet BS3621, the British Standard for thief-resistant lock assemblies. If your policy requires BS3621-compliant locks and your current locks do not meet that standard, you may find a burglary claim refused or reduced. The Secured by Design scheme maintains a list of products tested and certified to enhanced security standards. Specifying a Secured by Design-approved cylinder when upgrading gives you the highest available assurance on product performance.

For lock changing and cylinder upgrades across Croydon, Sutton, Kingston, Wimbledon and the wider South London area, call Experts Auto Locksmith. We will confirm which lock grade is appropriate for your doors, carry BS3621-compliant products, and complete the work to a standard that satisfies most insurer requirements.

Frequently Asked Questions

Do I legally have to change my locks when I move into a new home?

No, there is no legal requirement. However, it is strongly advisable. You cannot know how many key copies exist from the property's previous occupancy. Changing the cylinders before you move in is a straightforward precaution that most locksmiths recommend as a baseline.

What is BS3621 and why do insurers require it?

BS3621 is the British Standard for thief-resistant lock assemblies. It sets minimum performance requirements for deadlocks and cylinders, covering resistance to picking, drilling and other entry techniques. Many home insurance policies specify BS3621-compliant locks on external doors as a condition of cover. Non-compliant locks can affect your ability to claim.

How much does it cost to change the locks on a front door?

A cylinder replacement on a standard euro-cylinder or Yale-type lock typically costs £40 to £80 per lock, including parts and labour. Upgrading to a higher-security BS3621-compliant cylinder may add £20 to £40 to the parts cost. A full mortice lock replacement costs more and depends on door construction.

Should I change locks after a break-in even if the door was not the entry point?

Review all external locks after a break-in, not just the point of entry. A burglar who entered through a window may have assessed or interfered with door locks whilst inside. If there is any doubt about whether a lock was tampered with, replacing it is the prudent choice.