BS3621 Locks Explained — Why Your Home Insurance May Require One
Does your home insurance require a BS3621 lock? Many policies do — and many homeowners don't have one. Here's what it means and how to check.
Need help now? Call Ross directly — 24/7, no call centre.
07735 336175What Is BS3621?
BS3621 is the British Standard specification for thief-resistant locks. It was developed by the British Standards Institution (BSI) and has become the benchmark for residential lock security in the UK.
A BS3621 lock has been independently tested to resist common attack methods including:
It is also a five-lever lock — meaning it has five levers that must align correctly before the key turns, compared to the two levers in a standard budget lock.
Why Does Your Home Insurance Care?
Most standard UK home insurance policies contain a condition requiring a "five-lever mortice deadlock to BS3621 standard" on all final exit doors. If your door does not have a qualifying lock and you are burgled, your insurance company may reject the claim.
This is written into the small print. Many homeowners do not discover this until after a break-in.
The good news: a BS3621 lock costs £79 fitted (my price, no VAT, no call-out fee). That is a small amount compared to the risk of an invalidated insurance claim.
How to Check If You Have One
Look at your front door. If it is a wooden or composite door, look for a separate keyhole below the main door handle. This is typically where a mortice lock sits.
Turn the key. If the bolt extends from the edge of the door, you have a mortice lock. If there is a BS3621 mark on the lock faceplate or keyhole escutcheon, it meets the standard.
If you are not sure, call me and I will check it for you.
uPVC Doors and BS3621
uPVC doors almost never have a traditional mortice lock. They use a multipoint locking system — multiple bolts that lock into the door frame simultaneously.
Home insurance policies have evolved to recognise this. Most policies now accept a uPVC door with a multipoint lock and a cylinder meeting the TS007 three-star standard or Sold Secure accreditation as equivalent to a BS3621 lock.
If your uPVC door has a standard cheap euro cylinder, it is likely not meeting the standard. I can replace it with a TS007-rated anti-snap cylinder for around £59.
Getting a BS3621 Lock Fitted
I supply and fit BS3621 mortice deadlocks to all types of wooden and composite doors across Coventry and Warwickshire. Price from £79 including the lock and fitting. No VAT. No call-out fee.
Call 07735 336175 to book.
Frequently Asked Questions
Is one BS3621 lock enough or do I need two?
Most insurance policies specify a BS3621 lock on the main front door and a similar standard on the back door. Some policies require it on all final exit doors. Check your specific policy wording — or call me and I will advise.
Can I fit a BS3621 lock myself?
Technically yes — they are sold in DIY stores. However, fitting a mortice lock correctly requires chiselling a precise pocket into the door stile, which is easy to get wrong. An incorrectly fitted lock is less secure and may not meet the insurance standard. I recommend having it professionally fitted.
Does a BS3621 lock make my home more secure?
Yes, significantly. A five-lever BS3621 lock is substantially more resistant to picking and drilling than a standard two-lever or cheap cylinder lock. Combined with an anti-snap cylinder on your secondary lock, it provides a meaningful deterrent to most burglars.
About the Author
I'm Ross, a local independent locksmith covering Coventry, Nuneaton, Rugby, Leamington Spa, Warwick, and all surrounding areas. I've been working as a locksmith in the Coventry area for years and I've seen every type of lock problem there is. If you need a locksmith, call me on 07735 336175 — I'm available 24/7.