Choosing and Maintaining Window Locks for Your Home

Window locks are one of the most overlooked parts of home security. Most burglars enter through doors, but a significant proportion gain access through ground-floor and first-floor windows — particularly where locks are absent or original hardware has never been upgraded. This guide covers the types of window lock available, which British Standards are relevant, how fitting differs across window materials, and what basic maintenance keeps locks working year after year.

Why Window Security Deserves More Attention

According to Office for National Statistics data on domestic burglary, roughly a quarter of break-ins in England and Wales involve window entry. Builder-grade window hardware is designed to hold a window shut, not to resist a deliberate forced-entry attempt. A standard cockspur handle with no locking function can be defeated in seconds using a thin tool inserted through the frame gap. The cost of upgrading is modest — a set of key-locking window locks for a standard three-bedroom house costs between £60 and £150 in parts.

The Main Types of Window Lock

Sash Stops

Sash stops are small, screw-fitted devices preventing a sash window from being raised beyond a fixed point. They can be set to limit opening to 100mm (the figure commonly recommended where young children are present) or locked fully closed. They cost around £5 to £15 per unit and are one of the simplest additions available. Their limitation is modest resistance to a determined entry attempt — they function best as a deterrent against opportunistic entry or as a child safety measure.

Locking Cockspur Handles

The traditional cockspur handle on older casement windows uses a rotating lever that drops behind a striker plate to hold the sash closed. Without a locking version, this can be defeated by breaking glass adjacent to the handle or reaching through a frame gap. Locking cockspur handles incorporate a key-operated mechanism preventing the lever lifting without the key. These are available for £10 to £25 per handle and replace existing hardware directly.

Locking Handles for uPVC and Modern Casements

Modern uPVC casement windows use espagnolette locking systems where rotating the handle drives multiple locking points around the frame perimeter. The handle can incorporate a key-lockable mechanism, preventing window opening without a key. Quality locking handles from manufacturers such as Yale or Mila start at around £20. When selecting a replacement, match the spindle size and backplate dimensions of the existing handle precisely.

Key-Locking Window Locks

These are dedicated lock units screwed to the frame or opening sash. Key-locking window locks provide the highest security among standard window hardware and are the type most commonly required by home insurance policies. In many product ranges, one key operates multiple locks within the same series.

Which British Standards Apply

The relevant standard for enhanced window security is BS 7950, which covers performance requirements for window locks and restrictors, including assessment against defined manual-attack tests. The police-backed Secured by Design scheme sets specifications for window hardware used in new builds and refurbishments. Products carrying the Secured by Design mark have been tested to the scheme's performance criteria.

If your insurer requires window locks as a condition of cover, check specifically whether they require BS 7950-certified products or simply state "key-operated window locks." The distinction can matter if you need to make a claim following a window entry.

Fitting Locks on Different Window Materials

uPVC Windows

uPVC frames are hollow and reinforced internally with steel or aluminium inserts. Screws must reach the steel reinforcement to hold properly — fixings that bite only into the PVC itself will pull out under pressure. Use the correct screw length for the frame depth (typically 30 to 50mm) and locate the steel reinforcement before drilling. Self-tapping screws designed for uPVC are adequate for most installations.

Timber Windows

Timber frames accept standard wood screws and are the most forgiving material to work with. The main risk is fitting locks to frames that have softened due to rot or sustained moisture exposure. Check the timber at each intended fixing point — it should be firm and pale internally. If it is spongy or discoloured, address the rot before fitting any security hardware.

Aluminium Windows

Aluminium frames require specialist fixings — self-tapping metal screws or rivets. Some aluminium windows use a thermal-break design that creates a hollow cavity within the profile; fixings into this section will not hold reliably. If you are not confident about the frame construction, a locksmith experienced with aluminium window hardware is the right person to call. For local coverage in Sutton and South London, contact us for a window security assessment.

Maintenance Tips to Keep Window Locks Working

• Lubricate moving parts twice a year. Use silicone-based spray or light machine oil on the lock barrel, handle spindle and exposed hinge pivots. Avoid WD-40 as a long-term lubricant — it is a water displacer that dries out mechanisms over time. Purpose-made lock lubricant costs around £4 to £6.
• Check alignment regularly. A window that does not close fully often has a lock that cannot engage its striker plate properly. Most uPVC hinges have friction adjusters accessible with a 4mm hex key and can be tightened without specialist assistance.
• Test the key. If a key is stiff or binds in the barrel, treat it as an early warning of a failing mechanism. A barrel replacement costs very little; an emergency callout when a window has jammed locked costs considerably more.
• Inspect for corrosion. Urban and coastal properties see faster corrosion on metal window hardware. Surface rust can be treated with penetrating oil and light abrasion. Pitting or flaking on aluminium castings indicates the component should be replaced rather than maintained.

Frequently Asked Questions

Do I need a locksmith to fit window locks, or can I do it myself?

Most window locks can be fitted by a homeowner with basic tools and the correct fixings for the frame material. Where the frame is unusual, the existing hardware is non-standard, or your insurer requires BS 7950-certified products with a professional fitting record, using a locksmith is the more reliable option.

What is BS 7950 and why does it matter?

BS 7950 is the British Standard for enhanced security performance in window locks and restrictors. Products tested to this standard have been assessed against defined attack methods. Some home insurers require BS 7950-compliant locks as a condition of cover — check your policy before purchasing hardware.

Can a locksmith open a window lock if I have lost the key?

In most cases, yes. A locksmith can either pick or bypass the mechanism, or remove and replace the barrel. The method depends on the lock design. Bring proof of address when arranging this service, as the locksmith will need to confirm you are the occupier.

How much does window lock fitting cost in South London?

Basic fitting including parts and labour typically runs from £40 to £80 per window depending on lock type and frame material. When multiple windows are fitted in one visit, most locksmiths reduce the per-unit cost. Call for a clear quote before committing.