British Standard Locks: What BS3621 Means and Why Your Insurer Cares
If you've ever read the small print of a home insurance policy, you'll have seen a reference to BS3621. It's the British Standard for thief-resistant locks, and failing to have the right locks on your external doors could void your insurance cover without you even realising. Here's what {location} homeowners need to know.
What Is BS3621?
BS3621 is a British Standard (formally BS 3621:2007+A1:2009) that sets minimum performance requirements for locks used on external doors of domestic properties. A lock that meets this standard has been independently tested for resistance to:
- Picking — manipulation of the internal mechanism with specialist tools
- Drilling — attack on the cylinder or body of the lock
- Bumping — a technique using a specially cut key to bounce the pins into position
- Forced entry — physical attack including prying and levering
BS3621-compliant locks must also have a minimum of 1,000 key combinations and a key that cannot be copied without the owner's authority (restricted keyway).
Why Does Your Insurance Company Care?
Most UK home insurance policies include a condition that external doors must be secured with locks meeting BS3621 (or equivalent). If you make a burglary claim and your locks don't meet this standard, the insurer may:
- Reduce the payout
- Reject the claim entirely
- Void the policy from inception
This applies even if the burglar didn't enter through the non-compliant door. The condition is about meeting a minimum security standard across all external doors, not just the point of entry.
How to Check Your Locks
BS3621-compliant locks are marked with the BSI Kitemark and the standard number. Check for:
- On the lock faceplate (the metal strip visible on the door edge) — look for "BS3621" or the Kitemark symbol
- On the key — some manufacturers stamp the standard on the key head
- In the lock documentation — if you have the original packaging or receipt
If you can't find a marking, it's safest to assume the lock doesn't meet the standard. A locksmith can identify the lock and confirm whether it's compliant.
Types of BS3621 Locks
- 5-lever mortice deadlock: The classic British front door lock, fitted inside the door. The most common BS3621-compliant lock on wooden doors
- 5-lever mortice sashlock: Same as above but with a handle-operated latch as well as a deadbolt
- Euro cylinder locks (on multipoint systems): For UPVC and composite doors, the multipoint locking mechanism combined with a TS007 3-star cylinder typically meets or exceeds BS3621 requirements
What About UPVC Doors?
UPVC doors with multipoint locking systems (the type with hooks and bolts that engage at multiple points when you lift the handle) are generally considered equivalent to BS3621 by most insurers — provided the cylinder meets TS007 or SS312 standards. However, always check your specific policy wording and confirm with your insurer.
How Much Does Compliance Cost?
A qualified locksmith in {location} can supply and fit a BS3621-compliant mortice deadlock for approximately:
- Supply and fit to an existing cutout: £80–£140
- Supply and fit including cutting a new mortice: £120–£200
Given that non-compliance could invalidate a claim worth thousands, this is one of the most straightforward investments in home security you can make. If you're unsure about your locks, ask a locksmith in {location} for a security survey — most offer this as a quick, low-cost service.