The short answer
A BS 3621 lock is a lock that meets the British Standard for thief-resistant locks. It is made to resist drilling, picking and forcing for a set time. Many UK home insurers ask for a BS 3621 lock, or an equal standard, on the final exit doors of your home. If you do not have one and your home is broken into, your claim could be reduced or refused.
What does BS 3621 mean?
BS 3621 is the British Standard for thief-resistant lock assemblies that are opened with a key. Locks that pass the tests carry the BSI Kitemark and the number BS 3621 stamped on the faceplate, which is the metal plate you see on the edge of the door. On timber doors, the most common type is a five-lever mortice deadlock or sashlock.
How to check if your lock is BS 3621
- Open the door and look at the faceplate on the edge of the door.
- Look for the Kitemark symbol and the text "BS 3621". The year after it, such as 2007 or 2017, shows which version it meets.
- If there is no marking, assume it does not meet the standard.
- For a nightlatch, look for "BS 3621" on the lock case. Most standard nightlatches do not meet it.
Which doors need a BS 3621 lock?
Insurers usually mean the final exit door, the door you lock last when you leave, plus any other outside doors. Many policies also ask for key-operated locks on accessible windows. Wording varies, so read your policy or ask your insurer.
| Door type | What insurers usually accept |
|---|---|
| Timber front or back door | BS 3621 five-lever mortice lock, often with a nightlatch too |
| uPVC or composite door | Multipoint lock with a key-locking cylinder, ideally TS007 3-star or Sold Secure Diamond |
| Flat entrance door | BS 3621 mortice lock or BS 3621 nightlatch, if the door allows |
What about uPVC and composite doors?
BS 3621 was written for traditional locks. uPVC and composite doors use multipoint locks with a Euro cylinder, so insurers usually look at the cylinder instead. An anti-snap cylinder rated TS007 3-star or Sold Secure Diamond is the usual answer.
What a locksmith can do
A locksmith can check each outside door, tell you which locks meet your policy and fit BS 3621 locks or anti-snap cylinders where needed.
Related service: BS3621 lock change in London. Further reading: BSI Kitemark information.
A few common questions
What is a BS 3621 lock?expand_more
A BS 3621 lock is a key-operated lock that meets the British Standard for thief resistance. It is tested against drilling, picking and forcing. Approved locks carry the BSI Kitemark and the text BS 3621 on the faceplate. The most common type on timber doors is a five-lever mortice deadlock or sashlock.
Does my home insurance require a BS 3621 lock?expand_more
Many UK home insurers ask for a BS 3621 lock, or an equivalent standard, on final exit doors. Some also require key-operated window locks. The exact wording differs between policies, so read yours. If your locks do not meet it, a claim after a break-in could be reduced or refused.
How do I know if my lock is BS 3621?expand_more
Open the door and look at the metal faceplate on its edge. A compliant lock shows the Kitemark symbol and the text BS 3621, often followed by a year. If you cannot find any marking, assume the lock does not meet the standard and ask a locksmith to check it.
Do uPVC doors need BS 3621 locks?expand_more
uPVC and composite doors use multipoint locks with a Euro cylinder, so BS 3621 is not usually the test. Insurers normally accept a multipoint lock with a good key-locking cylinder. A TS007 3-star or Sold Secure Diamond anti-snap cylinder is the usual upgrade for these doors.
Is a nightlatch enough for insurance?expand_more
Usually not on its own. Most standard nightlatches do not meet BS 3621, and many insurers want a five-lever mortice deadlock on the final exit door. Some British Standard nightlatches do comply. A locksmith can check your door and suggest the right combination for your policy.