Door and window locks are the first line of physical security for any property. The UK has two distinct standards frameworks — one focused on insurer requirements for existing homes (BS 3621) and one on new-build security performance (PAS 24 and Building Regulations Part Q). Understanding both helps you make informed decisions whether you are upgrading an older property or specifying security for a new build or extension.
Insurers increasingly correlate lock quality with premium pricing, and some policies are invalidated outright if a break-in occurs through a door or window that did not meet their specified minimum standard.
Door Lock Standards
BS 3621: The Insurance Gold Standard
BS 3621 is the British Standard for thief-resistant mortice deadlocks. It specifies minimum requirements for bolt throw (at least 14 mm), material hardness, resistance to picking, drilling, and sawing, and key security (large key combination count to prevent duplication). Most UK home insurers specify BS 3621 as the minimum requirement for external doors.
A key distinction: BS 3621 applies specifically to mortice deadlocks — the type that lock when you turn the key and do not spring shut. A nightlatch (Yale-style) is not a deadlock and does not meet BS 3621 on its own, though combined BS 3621 nightlatches are available.
PAS 24:2022 — Enhanced Security Performance
PAS 24 (Publicly Available Specification) is a higher-performance standard covering the complete door set — lock, hinges, frame, and glazing — rather than just the lock cylinder. It specifies resistance to manual attack, tool attack, and cylinder manipulation. Door sets tested to PAS 24 are required for new dwellings under Building Regulations Part Q (see below).
PAS 24:2022 is the current revision, incorporating updated test methods reflecting modern attack tools.
Building Regulations Part Q
Part Q of the Building Regulations (England) requires that all new dwellings provide “reasonable resistance to unauthorised access.” In practice this means:
- Accessible ground-floor and first-floor windows and doors (including those reachable from a flat roof or adjacent structure) must meet PAS 24 or equivalent
- Door sets and window sets must be supplied by manufacturers who have tested to the relevant standard
- Part Q applies to new builds, extensions adding habitable rooms, and change-of-use conversions
Part Q does not apply to replacements in existing dwellings (where Building Regulations generally do not require security upgrades), but PAS 24 compliance is increasingly expected by insurers on new or recently replaced door and window installations.
Types of Door Lock
Mortice deadlock — fitted into a slot cut in the door edge. A BS 3621 five-lever mortice deadlock is the standard insurer requirement. Key-operated from both sides; the bolt does not move without the key. Suitable for timber doors with sufficient stile width (minimum 45 mm typically required).
Multipoint lock — used on uPVC and composite doors. A central handle engages multiple locking points (hooks, rollers, deadbolts) simultaneously along the door edge when the handle is lifted and the key is turned. Multipoint locks are inherently more secure than a single-point mortice on uPVC doors and are specified to PAS 24 on quality composite door systems.
Nightlatch (cylinder rim lock) — the familiar Yale-style spring latch. Alone it is not adequate as the primary lock; it must be supplemented by a deadlock. Combined BS 3621 versions (with deadlocking function) are available.
Euro cylinder — the removable barrel used in multipoint locks and some mortice locks. Standard euro cylinders are vulnerable to snapping attacks. Anti-snap cylinders (graded to TS 007:2014 3-star, or Sold Secure Diamond) are strongly recommended for any door using a euro cylinder. This is one of the most cost-effective security upgrades available.
Types of Window Lock
Cockspur handle lock — the traditional handle latch on older aluminium and uPVC casement windows. Lockable cockspur handles add a key lock to the standard handle, preventing the window being opened from outside. Very low cost; suitable for basic security in low-risk locations.
Casement espagnolette — modern uPVC casement windows use espagnolette (multi-point) locking mechanisms operated by a handle. When the handle is turned to the locked position and the key turned, multiple hooks engage the frame. This is the standard on PAS 24-compliant casement windows.
Sash window locks — vertical sliding sash windows have specific lock types: fitch catches (surface-mounted, key-operated), sash stops (prevent the window opening more than a ventilation gap), and sash bolts (mortice bolts fitted to the meeting rail). A combination of a key-operated fitch catch plus sash stops on each sash is recommended.
Tilt-and-turn window locks — tilt-and-turn windows have multi-point hardware integrated into the frame that locks when the handle is in the vertical (shut) position. Restrict-and-restrict position (horizontal handle) leaves the window in tilt mode only; full-open requires the key.
Sold Secure Ratings
Sold Secure is an independent testing body that grades locks and security products on three tiers:
- Bronze — resists opportunist attack with basic tools for a short period
- Silver — resists attack with more sophisticated tools for a longer period
- Gold — resists sustained, determined attack; suitable for high-risk locations
- Diamond — highest grade, reserved for the most attack-resistant products
For external door cylinders, aim for Sold Secure Gold or Diamond (or TS 007:2014 3-star). For window locks, Silver is adequate for most domestic locations.
Lock Types Comparison
| Lock type | Standard | Typical supply cost | Typical fitted cost | Suitable for | Insurer accepted |
|---|---|---|---|---|---|
| BS 3621 5-lever mortice deadlock | BS 3621 | £30–£80 | £80–£150 | Timber doors (45mm+ stile) | Yes |
| Anti-snap euro cylinder (Gold/Diamond) | TS 007 3-star / Sold Secure Gold | £20–£60 | £60–£120 | uPVC / composite doors | Yes (cylinder only — door set must also comply) |
| Multipoint lock upgrade (composite/uPVC) | PAS 24 (door set) | £80–£180 (lock body) | £150–£350 | uPVC / composite external doors | Yes |
| Nightlatch alone | None | £15–£50 | £50–£100 | Supplementary only | No (primary lock) |
| Casement espagnolette (PAS 24 window) | PAS 24 | £30–£80 per window | £60–£130 | uPVC / timber casement | Yes (as part of compliant window set) |
| Sash window fitch catch + sash stops | None (Sold Secure Bronze–Silver) | £10–£40 per window | £30–£80 | Vertical sash windows | Varies by insurer |
| Cockspur lockable handle | None (Sold Secure Bronze) | £10–£25 | £20–£50 | Older uPVC / aluminium casement | Basic only |
Secured by Design
Secured by Design (SBD) is a police-backed accreditation scheme that certifies entire products (doors, windows, frames, hardware) rather than individual locks. SBD Approved products have been independently tested to PAS 24 or equivalent. For new-build developers, specifying SBD-approved products is the simplest route to demonstrating Part Q compliance and can reduce insurance premiums for residents.
For homeowners replacing windows or doors, specifying SBD-approved products provides assurance that the whole unit — frame, glazing, hardware — has been tested together, not just the lock in isolation.
Practical Advice
The cylinder is often the weakest point. On any uPVC or composite door, replace the standard euro cylinder with an anti-snap TS 007 3-star cylinder. At £20–£60 supply plus £60–£100 to fit by a locksmith, it is the single best-value security upgrade available for most UK homes.
Timber doors in Victorian and Edwardian properties may have original rim latches and no deadlock. Adding a BS 3621 mortice deadlock (assuming sufficient stile width — measure before ordering) costs £80–£150 fitted and satisfies most insurer requirements.
Tell your insurer. If you upgrade your locks to meet BS 3621 or PAS 24, inform your insurer — you may be entitled to a premium reduction or removal of an exclusion clause.
French doors and patio doors are a common weak point. Multi-point locks and security glazing to PAS 24 are the appropriate specification; surface bolts at top and bottom provide additional resistance to forced entry.
Costs given are typical UK 2026 figures including VAT. Locksmith call-out and fitting costs vary by region; London and South East rates are typically 20–30% higher than the national figures shown.
