Window Lock Fitting Guide¶

Guide to fitting window locks on UK windows covering sash, casement, and tilt-and-turn types, with British Standard ratings and insurance-specific requirements for ground-floor security.

Window Lock Types for UK Homes¶

Key-operated window locks are essential for all ground-floor windows and any first-floor windows accessible from a flat roof, extension, or fire escape. The three main UK window types require different locks. Casement windows use a surface-mounted locking bolt or espagnolette locking handle. Sash windows require mortice sash locks, sash jammers, or dual screw locks. Tilt-and-turn windows have built-in multi-point locking but may need a key-operated handle upgrade. British Standard BS 7950 covers windows with enhanced security features. Most home insurance policies require key-operated locks on all accessible windows. Mila, ERA, and Yale are the leading UK window lock brands available at Screwfix, Toolstation, and B&Q.

Installation Guide for Common Window Types¶

For casement windows: measure the frame depth and choose correct size locking bolt. Position the lock plate on the frame and the keep on the opening window. Mark positions, drill pilot holes with 3mm bit for timber frames or 4mm for uPVC, and screw in place with supplied screws. Test the lock mechanism before closing for the first time. For sash windows: fit sash jammers on both sides near the meeting rail. These prevent the sashes from sliding past each other. For dual screw locks: drill through the inner sash into the outer sash and thread the key-operated screw. This locks both sashes together. Cost per window: 5-20 for basic locks, 15-40 for sash jammers. Installation time: 10-20 minutes for casement, 30-60 minutes for sash windows.

Specifications and Comparison¶

Window Type	Recommended Lock	Cost per Window	Difficulty
Casement uPVC	Key locking bolt	5-15	Easy
Casement timber	Surface lock	8-20	Easy
Sash timber	Sash jammer	15-40	Medium
Sash uPVC	Dual screw lock	10-25	Medium
Tilt and turn	Key handle	10-30	Easy

FAQ¶

Do I need window locks on first-floor windows?: Not necessarily. Standard insurance requirements cover ground-floor windows and any first-floor windows accessible from a flat roof, extension roof, or fire escape at the same height.
Can I fit window locks to uPVC windows?: Yes. Most uPVC casement windows have pre-drilled holes for lock fittings. Check the manufacturer compatibility guide at Screwfix or Toolstation before purchasing.
How do sash window locks work?: Sash jammers bolt the sliding sashes together preventing them from opening. They fit on both sides of the window near the meeting rail and are operated by a key. For more information see our Door Lock British Standards Guide.

Last updated: 2026-05-31.

External Resources¶

For further information consult authority guidelines at the UK Government Building Regulations.