Window Lock Faults Explained: Stiff, Broken or Not Closing

Last Updated: 16 October 2026

What to Check Before You Call About a Window Lock

Most window lock problems start the same way: a handle that won't turn, a window that won't pull shut, or a lock that feels loose in the frame.

A window lock is the mechanism that secures a window sash to its frame, usually through a handle, a gearbox and either a cam, a shootbolt or an espagnolette bar. When any part of that chain fails, the window either won't lock, won't close, or won't stay shut.

Before you call anyone out, run through this quick check:

• Does the handle turn at all, or is it stiff or seized?
• Does the window close flush against the frame, or is there a gap?
• Can you see any visible damage to the lock, hinge or handle?
• Has the window dropped, or does it catch on one corner?
• Is the fault on one window, or several in the same room?

If the handle turns but the window still won't lock, the issue is usually in the mechanism rather than the handle itself. If the window won't close at all, the problem is often alignment or hinges rather than the lock.

uPVC Window Lock Repair: Common Faults and How They're Fixed

uPVC window lock repair covers a narrow set of failures, and once you know them, diagnosis gets much faster. The most frequent faults are seized gearboxes, worn cams, snapped spindles, corroded shootbolts and misaligned keeps.

Here's what each one looks like in practice:

• Seized gearbox: the handle won't turn, or turns with heavy resistance. The internal cogs have worn or dried out.
• Worn cam: the window closes but won't lock. The cam no longer engages the keep properly.
• Snapped spindle: the handle spins freely with no resistance. The square bar connecting handle to gearbox has sheared.
• Corroded shootbolts: common on windows facing coastal weather. The bolts stick or won't extend.
• Misaligned keeps: the window locks but feels tight, or pops open under light pressure.

Repair-first is almost always the right call here. A gearbox, cam or spindle can usually be replaced on its own without touching the rest of the window. Replacing the whole window because of a worn cam is rarely necessary.

Window Lock Mechanism Repair: Espag, Cockspur and Shootbolt Systems

Window lock mechanism repair depends entirely on which system your window uses, because the parts aren't interchangeable. The three you'll meet most often are espagnolette, cockspur and shootbolt.

Espagnolette (espag) is the most common on modern uPVC windows. A single handle drives a long metal bar running the full height of the sash, with rollers or cams that engage keeps in the frame. When an espag fails, it's usually the gearbox at the centre or the bar itself.

Cockspur is an older design, still found on many timber and older uPVC windows. The handle sits on the sash and a spur on the handle engages a wedge-shaped keep on the frame. These are simpler, and often the whole handle is the mechanism.

Shootbolt systems use bolts that extend from the top and bottom of the sash into the frame. They're common on taller windows and patio-style units. Shootbolts are more prone to corrosion and misalignment than espag systems.

If you're not sure which system you have, look at the edge of the sash when the window is open. A long metal strip running top to bottom means espag. A single handle with a spur means cockspur. Bolts at the corners mean shootbolt.

Why Your Window Is Not Closing Properly (and What It Needs)

A window not closing properly is usually an alignment problem, not a lock problem. The lock can't engage if the sash isn't sitting square in the frame, so replacing the lock alone won't fix it.

The usual causes:

• Dropped hinges: the sash sags on one side, so the lock misses the keep.
• Swollen or warped frame: more common on timber, but can affect uPVC in extreme heat.
• Worn hinges or friction stays: the sash no longer pulls in tight.
• Loose or moved keeps: the locking point has shifted out of line.
• Debris in the track: grit or old paint stops the sash closing fully.

The fix depends on which of these is causing it. A dropped hinge usually needs adjusting or replacing, not a new lock. A misaligned keep needs repositioning. Only once the window closes flush should you look at the lock itself.

Window Handle Replacement: When a New Handle Is the Whole Fix

Window handle replacement is the right call when the handle is the only faulty part, and it's a quick job. If the handle is loose, cracked, seized, or the spindle has snapped inside it, a new handle often solves the problem outright.

Signs you need a new handle rather than a mechanism repair:

• The handle wobbles on its base
• The handle is cracked or the finish has failed
• The handle turns but nothing happens (snapped spindle)
• The handle is seized solid and won't budge even with the window open

Handles come in a few standard types, and matching the right one matters. You need the correct spindle length, fixing centres, and backplate shape. Getting this wrong means the handle won't sit flush or won't engage the gearbox.

If the handle turns freely but the window still won't lock, the fault is in the gearbox, not the handle. Replacing the handle in that case won't help.

How We Handle Window Lock Repairs: Step by Step

Here's how it works from the first call to the final test.

A stiff handle and a window that won't close can look similar but need very different fixes.

Step 2: Agree the price before we start. We tell you what needs doing and what it will cost. No call-out fee, no VAT to pay, and no surprises on the invoice.

Step 3: Repair first. Where a gearbox, cam, spindle or handle can be replaced on its own, we do that rather than pushing for a full window replacement. It's cheaper for you and just as secure when done properly.

Every repair we carry out comes with a 1-year warranty on parts and labour.

We're DBS checked and fully insured, so you know who's coming into your home.

A stiff window lock rarely fixes itself, and forcing it usually makes things worse. If your window won't lock, won't close, or the handle has stopped working, it's worth getting it looked at before the fault spreads to the rest of the mechanism.

At DW Locksmiths, we take a repair-first approach to window lock repairs, with no call-out fee, no VAT to pay, and a 1-year warranty on all parts and labour. We're DBS checked, fully insured, and we agree the price with you before any work starts.

Frequently Asked Questions

Can a window lock be repaired, or does it always need replacing?

Most window lock repairs are straightforward fixes rather than replacements. A stiff handle, a dropped sash or a misaligned keep is usually corrected by adjusting the hinges, lubricating the mechanism or replacing a single worn part. A locksmith will check the full locking strip before recommending anything new. At DW Locksmiths, the approach is repair first, so you only pay for a replacement when the mechanism is genuinely beyond saving.

How long does a window lock mechanism repair usually take?

Can I fix a uPVC window lock myself?

You can safely try simple steps: clean and lubricate the mechanism, check the handle screws are tight, and clear any paint or debris from the keep. If the window still will not close or the handle turns without engaging the lock, stop there. Forcing it can bend the locking strip and turn a small uPVC window lock repair into a full mechanism replacement. At that point, call a locksmith who carries the correct parts.

What should I do if my window will not close properly?

First, check for obvious obstructions and make sure the handle is fully in the closed position. If the sash is catching or the lock will not engage, do not force it, as this can damage the hinges and frame. Secure the room another way if you can, and book a repair. DW Locksmiths covers Sunderland, Washington, Seaham, Chester-le-Street, Peterlee, South Shields and surrounding areas, with no call-out fee and no VAT to pay.

Related DW Locksmiths services

• uPVC door lock repair
• Lock repair and replacement
• Window lock and handle repair

Call or WhatsApp DW Locksmiths on 07584 198906. No call-out fee, the price is agreed before work starts, and repairs come with a 1-year warranty with no VAT to pay.