uPVC Window Lock Repair and Replacement Explained

A broken uPVC window lock leaves your home vulnerable and can stop you opening the window for ventilation. The Master Locksmiths Association says uPVC window locks are the type they are called to repair most often, with typical 2026 repair costs starting from £69. This guide explains what goes wrong with window handles and locking mechanisms, and what it costs to put them right.

How uPVC window locks work

Most modern double glazed windows secure your home using a multipoint locking mechanism hidden inside the plastic frame. When you turn the handle, it rotates a square metal spindle. This spindle goes directly into a small central gearbox concealed in the edge of the window.

This gearbox drives a metal strip up and down the edge of the opening window. This metal strip is called an espagnolette window lock. As the espagnolette strip moves, small metal rollers or mushroom-shaped cams slide into metal keeps fixed to the outer window frame. Because the window locks at multiple points along its edge, it is highly secure against being forced open from the outside.

The handle itself usually contains a small cylinder lock. When you push the button or turn the key, this locks the handle in place so the spindle cannot turn. The window handle is the part you interact with daily, but the actual locking strength comes from the espagnolette mechanism inside the plastic frame.

Timber sash windows work differently. They slide vertically rather than swinging open on hinges. They are usually held by a catch where the two sashes meet, and on larger sash windows the MLA guidelines put extra locks on the meeting rail of the bottom sash or on the frame either side of the upper sash. Restrictors can hold them slightly open for ventilation, as covered below.

Common window lock faults

The window lock locksmiths are most often asked to repair is a uPVC window lock. They also routinely repair locks on double glazed, wooden and sash windows. Because uPVC windows are heavy and constantly exposed to the weather, things naturally shift and wear out over time. The most common problems reported to locksmiths are:

• A window that will not lock when the handle is turned.
• A window that will not open or close because the frame catches.
• A broken window lock handle that spins freely or has snapped off.

When a window fails, it is usually down to one of three things. First, the window hinges may have worn out or stretched. This causes the heavy opening frame to drop slightly, meaning the locking cams catch against the outer frame instead of sliding smoothly into their keeps.

Second, the internal gearbox that drives the espagnolette lock may have shattered. The internal parts are made of cast metal and will eventually break if they are repeatedly forced. Third, the handle itself may have snapped, or the square metal spindle inside it may have worn or sheared.

If you force a stiff handle, the internal mechanism will eventually break. A good locksmith will check how the window sits in its frame before replacing any locking parts. If the window has dropped, fitting a new lock without adjusting or replacing the hinges will just cause the new lock to break in the exact same way. A bad locksmith might drill the handle or quote for a whole new window when only one part has failed.

Handle will not turn or will not lock

If your window handle will not turn, the correct repair depends entirely on whether the window is currently open or closed. If the window is open and the handle moves freely, but it jams tight when you try to close and lock the window, the locking mechanism is out of alignment with the keeps on the frame.

This usually happens because the hinges have stretched or the frame has expanded in the summer heat. A locksmith will adjust the hinges or reposition the keeps so the rollers line up smoothly again. This is a routine adjustment and does not normally require new locking parts.

If the handle will not turn even when the window is wide open, the internal gearbox or the espagnolette strip has jammed. The handle is trying to drive a broken mechanism. In this case, the internal metalwork has failed and needs to be replaced.

Sometimes the handle turns freely in a full circle but the window does not lock or unlock. This means the spindle connecting the handle to the gearbox has snapped, or the internal mechanism has failed completely. If the window is locked shut, the locksmith will use non-destructive entry techniques to open the window safely. They will then remove the handle and inspect the gearbox to see which specific part needs replacing.

Lost or broken window keys

Losing your window lock keys is a common frustration, especially if you have just moved into a new house and nobody knows who holds the keys. Without them, you cannot open the windows for ventilation or to clean the glass.

If the window is locked closed and you have no key, do not try to pry the handle off or force it with a screwdriver. You risk cracking the uPVC frame or snapping the handle fixings, which turns a simple job into a very expensive one. A locksmith can usually pick or bypass the small cylinder lock in the handle to get the window open without causing any damage to the surrounding frame.

Once the window is open, you have two options. The first is to have a new key cut. The Master Locksmiths Association states that a window key costs from £4.75 and is normally cut in under five minutes. Many uPVC window handles use standard key profiles, so a locksmith may carry a pre-cut replacement window lock key that fits your handle perfectly.

The second option is a complete window lock replacement for the handle. The locksmith simply unscrews the existing handle and fits a new locking handle that comes with a fresh set of keys. This is often the cheapest and fastest route if the old handle was worn, or if it used an obscure key blank. If you have several windows in the same room, a locksmith can fit handles that are keyed alike. This means one single key will open every window, saving you from searching through a heavy bunch of keys.

If you rent your home, remember that a landlord who changes the locks to keep a tenant out without a court order commits illegal eviction, which is a criminal offence. Tenants should check their tenancy agreement and get the landlord's agreement before changing locks or handles on the property.

Repairing or replacing the locking mechanism

When the internal espagnolette mechanism fails, it must be removed from the edge of the window. This is straightforward when the window is open, but difficult when the window is locked shut and the handle will not turn.

A locksmith will use non-destructive methods to get the window open, taking care not to score the frame or put pressure on the glass. Once the window is open, they can take out the espagnolette strip from the edge of the window.

Often, only the central gearbox has failed. If the long metal strip and its rollers are still in good condition, the locksmith will simply swap the broken gearbox for a matching replacement. This saves money on parts. If the whole strip is rusted, bent or discontinued, they will replace the entire espagnolette mechanism.

There are many different uPVC window lock mechanisms in UK homes. They vary by length, by backset (the distance from the handle spindle to the edge of the frame), and by the type of locking cams they use. A locksmith may carry common sizes or a universal repair mechanism that can be cut to length, but some mechanisms have to be ordered. Just as you might call a professional to diagnose uPVC door lock problems, it pays to have an expert match the exact window lock mechanism to your specific frame.

If your window is stuck open and the specific espagnolette lock has to be ordered in, a locksmith can securely board up the opening or fit temporary locks to keep your home safe until the part arrives.

How many locks a window should have

The Master Locksmiths Association publishes minimum security guidelines that detail exactly what is expected for ground floor and easily accessible windows. Insurers often ask what locks are fitted, so check your own policy wording to ensure your windows meet their specific requirements.

The MLA guidelines depend on the size of the opening window. If the opening window is over 600mm high or wide, it should have a multipoint locking system or two window locks with removable keys. If the opening window is under 600mm, it needs only one lock.

The guidelines state that acceptable locking options for these accessible windows include:

• A window lock with a removable key.
• A substantial locking handle with a removable key.
• A multipoint locking system with a removable key.
• A complete window certified to the PAS 24 security standard.

If you fit a window lock restrictor to stop the window opening wide enough for someone to climb through, it must be secure. Police security guidance states that window opening restrictors must not be able to be disengaged from the outside.

For vertical sliding sash windows, restricting devices can be fitted to allow a ventilation opening of no more than 100mm. However, the guidelines state that the window should be fully closed and secured when the home is unoccupied.

Window locks and getting out in a fire

Security must always be balanced against fire safety. You must always give yourself a means of escape in a fire, and locked windows can trap you inside if you cannot find the key in an emergency.

The government fire safety campaign Fire Kills advises that you should keep door and window keys in a safe but accessible place near the exit. Make sure everyone in the household knows exactly where they are. Never leave keys in locks where they could fall out or be hard to find in the dark or in heavy smoke. You should also make sure you do not let clutter block windows that you might need to use as an escape route.

The Master Locksmiths Association guidelines are strict on this point. A window required for emergency escape should not be fitted with any key lockable system. Instead, it should have laminated glass fitted to provide security without needing a locked handle.

If you are moving into a new home or having new windows fitted, check which windows are designated as fire escapes. These are typically on the upper floors. Ensure they have push-button handles rather than key-locking handles, so anyone can open them instantly from the inside without searching for a replacement window lock key.

What window lock repairs cost

Locksmiths usually price window repairs as a combination of labour and parts. The final price depends on whether the window just needs realigning, whether a handle needs swapping, or whether a full espagnolette mechanism is required. Prices are driven by the time of day, with evenings, nights, weekends and bank holidays costing more. Location also matters, as London and the South East cost more than other areas.

This table shows typical costs for window lock parts and repair labour across the UK.

These figures are typical published prices for 2026. Local quotes will differ based on the exact mechanism required, your location, and the time of day.

According to the Master Locksmiths Association price guide, the average price for a uPVC window lock repair starts from £69. Many locksmiths do not charge a separate call-out fee, but some do. Most single lock changes and lockouts take well under an hour to complete.

When you ask a locksmith for a quote, describe the problem clearly. Ask for a total price that includes the labour, the replacement parts, and VAT. Not all locksmiths charge VAT, so you must ask whether it is included in the price they quote on the phone. Under the Consumer Rights Act 2015, a service must be carried out with reasonable care and skill, at a reasonable price if none was agreed, and within a reasonable time. You have a right to have poor work put right or your money back.

Under the Consumer Contracts Regulations 2013, there is normally a 14-day cancellation period for work arranged at home or by phone. However, this does not apply where you specifically ask for a visit for urgent repairs. If your window is stuck open at night and you cannot secure the house, you may have to pay a higher emergency out-of-hours rate. If the window is locked shut and secure, the job can usually wait until the daytime rate applies.

When it makes sense to replace the window

Sometimes a window lock repair is not enough. If your uPVC window frames are heavily discoloured, cracked, or the hinges are so warped that the window no longer sits squarely in the frame, replacing the lock will only be a temporary fix. When frames are failing, replacing the whole window may be better than repairing the lock.

If you decide to replace the windows entirely, security should be a priority. Police crime prevention advice says anyone replacing windows should consider a security accredited product to a standard such as PAS 24:2022. This means the window has been rigorously tested against physical attacks and attempts to pry the locking points apart.

If you are building a new home in England, legal requirements apply to the windows you install. Approved Document Q of the Building Regulations says ground floor, basement and other easily accessible windows should be made to a design shown by test to meet PAS 24.

This building regulation applies to new dwellings only. It does not apply if you are simply replacing an existing window in an older property, though police advice is to consider a security accredited window such as PAS 24 when replacing one.

Common questions

What is a window espagnolette lock?

An espagnolette lock is the metal strip hidden inside the edge of a uPVC or composite window. When you turn the window handle, it drives this strip up and down, pushing locking cams into the frame to secure the window at multiple points.

Can you replace a uPVC window lock mechanism?

Yes, a locksmith can replace the internal locking mechanism without replacing the whole window. They will remove the old espagnolette strip or central gearbox and fit a new one that matches the length and locking points of your frame.

How do I fix a broken window lock restrictor?

A broken restrictor should be replaced rather than patched, and police advice is that a restrictor must not be able to be released from outside. On a window you might need to escape through in a fire, make sure the restrictor can be released quickly from inside.

How much does a replacement window lock key cost?

A standard replacement window key cut by a locksmith costs from £4.75. If the keys are completely lost and the window is locked, a locksmith can usually open it without damage and fit a new locking handle with new keys. You can find more detail in our guide on how much key cutting costs.

Next steps before you hire a locksmith

When your window will not lock or you have lost the keys, a professional can usually fix the problem in under an hour. Keep these points in mind before you agree to any work:

• Ask for a total price over the phone that includes labour, parts and VAT.
• Check whether the locksmith charges a separate call-out fee just for turning up.
• Explain exactly what the window is doing, whether it is stuck open or closed, and whether the handle turns.
• Ask if they carry standard uPVC window lock mechanisms and handles on their van to complete the job in one visit.
• Check that the business has a real local address and consistent reviews over time.
• Ask for identification when they arrive and a written invoice when the job is done.

There is no government licensing for locksmiths in the UK, so anyone can trade as one. The Master Locksmiths Association operates a voluntary approval scheme where companies are vetted and inspected regularly. Choosing a vetted professional protects you from being overcharged or having your window damaged unnecessarily. When you are ready to get your window secured, you can find a locksmith near you to get a firm price for the repair.