UK home and commercial locks are governed by a small set of British Standards and security ratings — most homeowners never read them, then discover after a burglary that their insurer expected specific compliance. The standards aren't complicated once you know which one applies to which door. This guide breaks down all five (BS3621, BS8621, BS10621, TS007, Sold Secure SS312 Diamond), explains who they're for, and tells you how to check what's on your own door.
The five standards in one paragraph
- BS3621: Mortice locks, key both sides. Standard for residential wooden external doors.
- BS8621: Like BS3621 but with thumb-turn for keyless exit. Required on most commercial premises, HMOs, flats — anywhere a fire-escape route applies.
- BS10621: Locks only from the outside (key required); can leave from inside without locking. Niche use — typically holiday cottages or low-occupancy properties.
- TS007: Standard for euro cylinders (UPVC and composite doors). Rated 1, 2, or 3 stars — 3-star is the highest.
- Sold Secure SS312 Diamond: Independent UK rating for euro cylinders that pass above and beyond TS007. Police "Secured by Design" recommended.
BS3621 — mortice locks (wooden doors)
The British Standard for mortice locks fitted into wooden external doors. Requirements include:
- At least 5 levers (older locks often have 2 or 3)
- Hardened steel bolt that resists sawing
- At least 1,000 differs (key combinations) to prevent brute-force trial
- Resistance to forced attack for a specified minimum time
Look at the metal faceplate (the rectangle around the bolt on the edge of the door). A BS3621 lock has the British Standard Kitemark logo and "BS3621" stamped on it. If it just shows the manufacturer name with no BS reference, it's almost certainly not BS3621-compliant.
Required for: Most UK home insurance policies on wooden external doors. Lockable both sides with key — no thumb-turn.
BS8621 — same security, with fire-escape exit
BS8621 covers locks that meet the same forced-entry resistance as BS3621 but allow keyless exit from inside (typically via a thumb-turn or push-pad). This is a fire-safety requirement on premises where occupants must escape quickly:
- Flats and apartments
- HMOs (Houses in Multiple Occupation)
- Shops, cafés, restaurants, offices with public access
- Holiday lets and B&Bs
- Care homes and similar
If your premises has any of these uses, you almost certainly need BS8621 on the final exit door — not BS3621.
BS10621 — lock from outside only
Niche standard for premises where you want to be able to leave without locking but lock when going out. Typically used in:
- Single-occupancy holiday lets where guests come and go via a different door
- Low-occupancy commercial premises
- Some flats where the building's main entrance has its own security
Rare in residential Cornwall but worth knowing exists. The bolt only operates from outside; inside, the latch is the only locking mechanism.
TS007 — euro cylinders (UPVC and composite doors)
TS007 is the technical specification for euro cylinders (the cylindrical brass bit on either side of UPVC/composite doors). Star ratings:
- TS007 1-star: Anti-pick and anti-bump protection. Not enough alone for insurance.
- TS007 2-star: Applied to door handles, not cylinders. Pairs with 1-star cylinder to make a 3-star total.
- TS007 3-star: Anti-snap, anti-pick, anti-bump, anti-drill in the cylinder alone. The simplest path to insurance compliance.
The big concern with euro cylinders is lock snapping (see our anti-snap upgrade guide). TS007 3-star cylinders are engineered with a sacrificial front section that breaks off uselessly under attack while leaving the cam intact.
Check the cylinder body for stars stamped near the keyhole:
- No stars: standard non-rated cylinder — vulnerable
- 1 star: needs paired 2-star handle for compliance
- 3 stars: fully compliant alone
Sold Secure SS312 Diamond — beyond TS007
Sold Secure is an independent UK testing body endorsed by the Master Locksmiths Association. Their SS312 Diamond rating goes above and beyond TS007 — Diamond cylinders pass attacks that TS007 3-star tests don't cover. Police "Secured by Design" certification typically follows from Diamond rating.
Best cylinders carry both TS007 3-star AND Sold Secure SS312 Diamond. Brands: Avocet ABS, Brisant Ultion, Yale Platinum.
What your insurance likely requires
Read your home insurance policy schedule. Look for sections titled "Security requirements", "Locks specification", or "Conditions". Common requirements:
- Wooden external doors: BS3621 5-lever mortice lock
- UPVC/composite external doors: BS3621 multipoint mechanism OR TS007 3-star cylinder (some policies accept 1-star cylinder + 2-star handle)
- Patio/French doors: Locks meeting PAS 24 OR secondary locking devices (e.g., key-operated patio locks)
- Windows: Key-operated locks on all accessible windows
- Commercial premises: BS8621 on final exit doors (fire-safety compliance)
If your locks don't meet the policy specification, claims can be refused or reduced after a burglary. Worth checking the schedule and upgrading any gaps.
How to check your own locks
- Wooden front door (mortice): Open the door, look at the metal faceplate on the door edge. BS3621 Kitemark + "BS3621" stamped = compliant.
- UPVC or composite door (euro cylinder): Look at the brass cylinder body near the keyhole. Look for star markings. 3 stars = TS007 compliant. Look also for "Sold Secure SS312 Diamond" or the Diamond logo.
- Commercial / HMO / flat: Check the final exit door has a thumb-turn (BS8621). If it has key-both-sides (BS3621), you may have a fire-safety compliance issue.
What it costs to upgrade in Cornwall
| Upgrade | Cost |
|---|---|
| BS3621 mortice lock fitted (per door) | £120-£200 |
| BS8621 mortice + thumb-turn (commercial) | £140-£220 |
| TS007 3-star cylinder fitted | £100-£180 |
| Sold Secure Diamond cylinder fitted | £110-£200 |
| Full house compliance (3-bed) | £300-£600 |
Want a Cornwall locksmith to audit your locks for insurance compliance? Submit your postcode — we'll match you with a locksmith who'll inspect, identify gaps, and quote any upgrades needed with itemised pricing.
Frequently asked questions
What's the difference between BS3621, BS8621, and BS10621?
All three meet the same forced-entry resistance standard but differ on how they unlock from inside. BS3621: key both sides (residential standard). BS8621: thumb-turn or push-pad for keyless exit (commercial, HMO, flats — fire-safety requirement). BS10621: only locks from outside (niche, low-occupancy premises).
What's TS007 3-star?
The highest UK star rating for euro cylinders (UPVC and composite doors). Means the cylinder passes anti-snap, anti-pick, anti-bump, and anti-drill tests. 3-star alone is sufficient for most home insurance; 1-star cylinder + 2-star handle is an equivalent combination.
What does Sold Secure Diamond mean?
An independent UK rating from Sold Secure (endorsed by the Master Locksmiths Association) that goes above and beyond TS007 — Diamond cylinders pass attacks TS007 3-star doesn't cover. Diamond-rated cylinders are 'Secured by Design' approved (police-recommended). Best practice: get a cylinder with both TS007 3-star and Sold Secure Diamond.
How do I know what standard my locks meet?
Mortice locks: look at the metal faceplate on the door edge — BS3621 Kitemark and 'BS3621' stamped. Euro cylinders: look at the brass cylinder body near the keyhole — star markings (1, 2, or 3 stars), TS007 logo, Sold Secure Diamond logo. No markings = unrated and probably not insurance-compliant.
What if my locks don't meet my insurance requirements?
Two scenarios: nothing happens (no claim, no impact), or you make a burglary claim and the insurer investigates the locks. If non-compliant, the claim may be refused, reduced, or the policy voided. Upgrading is cheap (£300-£600 for a 3-bed) compared to an average UK burglary claim (£3,500+).