Insurance Approved Locks Explained — A Locksmith's Guide for Hertfordshire Homeowners

Not sure if your locks are insurance approved? Chris from Moore Secure Locksmiths explains British Standard locks, deadlocks, euro cylinders and window locks in plain English

What Does "Insurance Approved" Actually Mean?

If you've ever read through your home insurance policy, you've probably come across the phrase "insurance approved locks" — and wondered exactly what that means for your front door. It's a term that causes a lot of confusion, so let me clear it up.

No lock is literally approved by your insurance company. What insurers actually look for is whether your locks meet a recognised British Standard — most commonly BS3621. If they do, they're generally accepted as meeting the minimum security requirement. If they don't, and you're burgled, your insurer may reduce your payout or reject your claim entirely. It's worth knowing before something goes wrong.

What Is BS3621?

BS3621 is the main British Standard for thief-resistant locks on external doors. It's set by the British Standards Institution (BSI) — an independent body that tests and certifies products against strict criteria. The current version is BS3621:2017+A1:2024, though any Kitemarked BS3621 lock is generally acceptable to insurers.

For a lock to carry the BS3621 Kitemark, it must meet the following requirements:

- At least five levers (for mortice locks) or equivalent pin tumblers

- A bolt that projects at least 20mm into the door frame

- Resistance to drilling with standard tools for a minimum of five minutes

- An anti-pick mechanism

- A minimum of 1,000 different key cuts, so the chances of someone having a matching key are extremely low

- Fixings that cannot be accessed when the door is closed

You can check if your lock is BS3621 by opening your door and looking at the metal faceplate on the edge. A compliant lock will have the BSI Kitemark symbol and the number BS3621 stamped directly onto it.

Deadlocks vs Cylinders — What's the Difference?

There are two main types of lock you'll find on external doors in the UK, and the right one depends on your door type.

A five-lever mortice deadlock is the traditional lock found on wooden doors. It sits inside the body of the door itself, operated by a key from both sides. This is the most common BS3621-compliant lock for timber doors and what most insurers are referring to when they mention "insurance approved locks." A three-lever mortice lock is NOT BS3621 compliant — it must be five levers.

A euro cylinder is the long oval-shaped lock you'll find on uPVC and composite doors. The cylinder itself is what gets replaced when you upgrade security. For euro cylinders, the relevant standard is different — you want to look for TS007 3-star rated or SS312 Diamond Approved cylinders, which are specifically tested for anti-snap, anti-drill, anti-pick and anti-bump resistance. For multipoint locking systems (the long strip of locking points down a uPVC door), the equivalent standard to BS3621 is PAS3621.

One important point on euro cylinders: lock snapping is one of the most common break-in techniques used on uPVC and composite doors in the UK. A standard euro cylinder can be snapped in seconds with basic tools. If your door has a euro cylinder, upgrading to an anti-snap cylinder is one of the most important security improvements you can make — and it's quick and affordable.

What About Flats and Communal Doors?

If you live in a flat, the standard BS3621 deadlock isn't always appropriate. BS3621 requires a key to open the door from both sides — which can be a fire safety issue in a communal building. For flats, the correct standard is usually **BS8621**, which allows a thumbturn on the inside so you can exit quickly without a key. Check your insurance policy carefully if you live in a flat, as requirements can differ.

Do Window Locks Need to Be Key-Operated?

This is one of the questions I get asked most often, and the short answer is: for insurance purposes, yes — for accessible windows at least.

Most insurers require key-operated locks on all ground floor windows, and any window that can be reached from a flat roof, balcony or outbuilding. "Accessible" is the key word — your insurer is generally not concerned about a skylight three storeys up, but they will expect your kitchen, living room and ground floor bedroom windows to be secured.

For uPVC casement windows, the handle lock alone is often not enough — a secondary key lock or window restrictor is recommended. For sash windows, a dedicated sash lock or Brighton sash fastener is the standard solution. French doors need particular attention — most insurers require key-operated mortice rack bolts at the top and bottom in addition to the main lock.

If your windows have locks but they're not key-operated, it's worth checking your policy wording. Some insurers will accept other security devices, but key-operated locks are always the safest option.

What Should I Tell My Insurer?

When you take out or renew your home insurance, you'll typically be asked about the types of locks on your doors and windows. It's essential to answer accurately — giving incorrect information (even unintentionally) can invalidate a claim.

Here's what to check before you fill in your policy:

- Do your external wooden doors have a five-lever mortice deadlock with the BS3621 Kitemark?

- Do your uPVC or composite doors have an anti-snap euro cylinder (TS007 3-star or SS312 Diamond)?

- Do your accessible windows have key-operated locks?

- Are all locks properly fitted and in good working order?

If you're not sure what you have, or if your locks are older and you've never had them checked, it's worth having a locksmith carry out a quick security survey. I offer these free of charge across Borehamwood and the surrounding Hertfordshire area.

The Bottom Line

Locks are one of those things most people don't think about until something goes wrong. But getting them right protects both your home and your insurance policy. The key points to remember:

- BS3621 is the standard for wooden door locks — look for the Kitemark on the faceplate

- For uPVC and composite doors, focus on anti-snap cylinders rated TS007 3-star or SS312 Diamond

- Window locks on accessible windows should be key-operated

- Always check your policy wording — requirements vary between insurers

- If in doubt, speak to an MLA-qualified locksmith before your renewal date

If you'd like me to check your locks and confirm whether your home meets your insurer's requirements, give me a call on 07939 022528 or get in touch. I cover Borehamwood, Radlett, Barnet, Elstree and all surrounding areas.