BS3621 is the British Standard your insurer references when they require approved locks on all external doors. Here is exactly what it means, which locks qualify, and what happens if yours do not comply.
What Is BS3621?
BS3621 (full reference: BS3621:2007+A2:2012) is a British Standard specification for thief-resistant locks. A lock carrying this standard has been independently tested against picking, drilling, sawing and the use of keys cut from photographed profiles.
BS3621 is the standard most commonly cited in UK residential insurance policies. When a policy states approved locks on all external doors, it is referring to this certification.
Which Locks Qualify?
**Five-lever mortice deadlocks** — set into the door body, requiring a key to lock from outside. Five levers directly affects pick resistance. BS3621-certified models from Union, Chubb, ERA and Yale are the standard choice for timber external doors.
**Rim deadlocks** — surface-mounted versions used on some older properties.
Euro cylinders (found in UPVC and composite doors) are covered by a different standard: TS007 for anti-snap performance. A TS007 3-star cylinder within a multipoint mechanism is widely accepted by insurers as the UPVC equivalent of a BS3621 mortice.
Insurance Implications
If a claim is made following a burglary and the entry point did not have BS3621-compliant locks, the insurer may reduce or refuse the payout. This is stated in the small print of most standard household policies.
How to Check Your Locks
Look for the BS3621 marking on the lock face plate or body. If you are uncertain, a locksmith can identify your locks in minutes — TrustLock checks lock compliance as part of any service visit at no extra charge.
Upgrade Costs in Dulwich and South London
Most homes need one or two upgrades to cover all external doors. Call 07984 547185 for a fixed quote.