If you have ever read your home insurance policy closely, you may have spotted a requirement for locks that meet “BS3621”, or for a “British Standard five-lever mortice deadlock” on your final exit doors. It is one of the most commonly quoted lock requirements in UK home insurance. This guide explains what the standard means, how it relates to other lock standards, and how to check whether the locks on your doors are likely to match what your policy asks for.
What BS3621 is
BS3621 is the British Standard for thief-resistant locks that are locked and unlocked with a key from both sides. In practice, it most often applies to mortice deadlocks and mortice sashlocks set into the edge of a timber door, and to some rim-mounted deadlocks and nightlatches.
Locks certified to BS3621 have been tested for resistance to common attacks such as drilling, picking and forcing, and must meet requirements such as a minimum number of key variations. A compliant lock is marked on its faceplate — the metal strip visible on the edge of the door when it is open — with the Kitemark and the standard number.
“Five-lever” is not the same as BS3621
Over the years, “five-lever mortice deadlock” has become a shorthand for an insurance-approved lock. But having five levers is not the same thing as meeting the standard. A lock can have five levers and still not be certified to BS3621. The Kitemark and the standard number on the faceplate are what show that a lock has been tested and approved.
If your policy wording says “BS3621”, look for that marking rather than relying on the number of levers.
BS8621 and BS10621
Two related standards come up regularly:
- BS8621 covers locks that offer similar security from outside but can be opened from the inside without a key, usually with a thumbturn. They are designed for situations where people need to be able to leave quickly, such as flats and houses in multiple occupation, where fire safety arrangements call for keyless exit.
- BS10621 covers dual-mode locks. In normal use they open from the inside with a thumbturn, but they can be switched to a mode where the inside cannot be opened without a key — for example when the property is left empty.
Some insurers accept these as alternatives to BS3621. Whether yours does is a question for your insurer or broker.
What your insurer is actually asking for
Policy wording varies a great deal. Some policies set specific requirements for final exit doors — the doors you leave by and lock behind you — with separate requirements for other external doors and for windows. Others are more general. Where a policy does set lock conditions and they are not met, a burglary claim could be reduced or refused, particularly where there are no signs of forced entry.
The only reliable way to know what applies to you is to read your policy schedule and wording, or to ask your insurer or broker directly. A locksmith can tell you what is fitted to your doors and what standard it meets; we cannot tell you what your policy requires.
What about uPVC and composite doors?
BS3621 was written with key-operated locks on timber doors in mind. Most uPVC and composite doors use a multipoint locking system operated by a euro cylinder, which BS3621 does not directly apply to.
Many insurers accept multipoint locking on these doors instead, and some refer to the cylinder standard — typically TS007 3 star or Sold Secure Diamond. You may also see references to PAS 24, a performance standard that applies to complete door sets rather than individual locks. If your policy mentions BS3621 and your front door is uPVC, it is worth asking your insurer what they accept for that type of door. Our guide to anti-snap locks, TS007 and Sold Secure Diamond explains those cylinder ratings in more detail.
How to check the locks on your doors
You can do a quick check yourself:
- Open each external door and look at the faceplate on the edge of the door.
- Look for the Kitemark and “BS3621” — or BS8621 or BS10621. A model number next to it is normal.
- On uPVC and composite doors, look at the face of the cylinder for TS007 stars or Sold Secure markings.
- Write down what you find for each door and compare it with your policy wording.
If the markings are worn, painted over or missing, a locksmith can usually identify the lock and tell you whether it meets a recognised standard.
When upgrading makes sense
There are a few common moments when it is worth checking and, if needed, upgrading:
- Moving in. You do not know the history of the locks or who has keys.
- Renewing or switching insurance. A new policy may word its lock requirements differently from your old one.
- After a break-in. Repairs are a natural point to bring locks up to standard rather than simply replacing like for like. Our burglary repairs service covers this.
- Worn locks. A lock that sticks or needs jiggling may not be giving you the protection it should.
On timber doors, a non-compliant mortice lock can often be replaced with a BS3621 lock using the existing cut-out in the door, depending on the sizes involved. Occasionally the door needs a little extra work to fit the new lock properly, and we will tell you before we start if that is the case.
How we can help
We fit British Standard mortice deadlocks on timber doors and certified cylinders on uPVC and composite doors, and we will explain what is going in and why. See our lock replacement and security upgrades page for more detail, or check the areas we cover across Essex and East London. To talk through your doors, call 07500 582013.