Window Lock Repair and Replacement

Windows Are the Second Most Common Point of Entry After Doors

Home insurers pay close attention to window security, and for good reason. After doors, windows are the second most common point of entry for residential burglaries. Ground-floor windows, particularly those that are partially obscured from the street or a neighbour's sightline, represent a meaningful vulnerability in most residential properties.

Most UK home insurance policies require window locks on all opening ground-floor windows and, often, first-floor windows that are accessible from an adjacent flat roof, outbuilding, or extension. The specific standard varies by insurer, but key locks — those requiring a key to open — are typically specified rather than simple espagnolette latches.

The Most Common Window Lock Types and Their Failures

UPVC Casement and Tilt-and-Turn Espagnolettes

The espagnolette is the multi-point locking strip running around the inside of a UPVC window frame. Failures include broken gearboxes (the handle turns but the locking points don't move), individual lock points that have snapped or jammed, and seized or corroded mechanisms on older UPVC windows. Many espagnolette components are interchangeable across manufacturers, making repair more straightforward than full window replacement.

Sash Window Stops and Lifts

Timber sash windows rely on sash stops (which limit how far the sash can be opened) and sometimes secondary security locks. Older properties often have original fittings that have never been updated. A modern sash stop that limits the window to 100mm opening — sufficient for ventilation but not for entry — is an inexpensive addition that many insurers will expect.

Key Locks vs Espagnolette Latches

An espagnolette latch (the standard lever handle on most UPVC windows) does not require a key to operate. While it secures the window when engaged, it provides no resistance to being opened from outside if the window is forced. A key lock — sometimes retrofitted as a surface-mounted device alongside the existing latch — adds a requirement for a key, significantly increasing forced-entry resistance.

Checking Insurance Requirements

Before commissioning window lock work, check your policy schedule for specific requirements. Common specifications include:

• Key-operated locks on all accessible ground-floor windows
• Key-operated locks on first-floor windows accessible from flat roofs, outbuildings, or extensions
• A maximum opening restriction of 100mm on windows in occupied rooms
• BS 7950 compliance for window locks (though this standard is less universally cited than BS 3621 for door locks)

Confirming requirements before work begins ensures the locksmith fits the correct product — not just a functional lock, but one that meets your insurer's specific standard.

Locksmith vs Window Installer

A locksmith is the right call for: repairing existing window lock mechanisms, fitting additional security locks to existing windows, and assessing and advising on window security as part of a broader property security review. A window installer is more appropriate for full window replacement, failed double-glazed sealed units, or UPVC frame damage that has compromised the integrity of the window. The two trades sometimes overlap on UPVC mechanism work, but for lock-specific issues, a locksmith will usually be faster and more cost-effective.