A common cause of gearbox failure is forcing the handle on a composite door that has dropped, so the locking points miss the keeps and the force goes through the gearbox. A lock repair or a replacement gearbox starts from £85, though prices vary by area and time of day. Knowing whether the stiffness is in the door or the lock itself will help you decide what to do next.
How a composite door lock works
Unlike a traditional timber door, which usually relies on a mortice deadlock and a sashlock fitted inside the wood, or a night latch or rim lock on the surface with a rim cylinder, composite doors use a multipoint locking mechanism. This is a long metal strip of hooks and bolts hidden down the edge of the door, worked by lifting the handle. According to the Master Locksmiths Association, these systems usually have a minimum of three locking points, and sometimes four or five.
When you close the door, you must lift the handle to push the hooks or bolts out into the metal keeps on the frame. Once the handle is lifted, you turn the key in the barrel to lock the mechanism in place. This barrel is the euro cylinder.
The central part of the long metal strip, which turns the movement of the handle and the key into the movement of the hooks, is called the gearbox. It is vital to lift the handle and double lock the mechanism with the key before you go to bed or leave the house. If the locking system does not lock properly, your home insurance may not cover any losses from a break-in.
Signs your lock is struggling
A failing lock may show some of these signs before it breaks completely. You might notice one or more of these common symptoms as the mechanism starts to wear out:
- The handle droops or feels floppy instead of sitting horizontally.
- Lifting the handle takes more physical effort than it used to.
- You have to push or pull the door hard to get the lock to engage.
- The key turns but the lock does not engage.
- You hear a clicking or grinding noise from inside the door.
- Some locking points do not fully retract when you push the handle down.
- The handle spins freely and does nothing, meaning the gearbox has probably failed.
If the handle spins freely, the gearbox has probably failed, and you will need a professional to deal with the door.
The door has dropped
A door that has dropped out of alignment with its frame is a common cause of lock problems. Composite doors are heavy, and over time their weight can cause the hinges to sag slightly. Normal wear, a dry mechanism and seasonal temperature changes all contribute to the door and the frame expanding and contracting, altering how they sit together.
When the door drops, the hooks and bolts on the locking strip no longer line up perfectly with the metal keeps on the frame. As you lift the handle, the locking points hit the edges of the keeps instead of sliding smoothly into them. This creates resistance, which you feel as a stiff handle.
The clearest clue that the door has dropped is how the handle feels when the door is open compared to when it is shut. If the handle is completely smooth and easy to lift when the door is open, but stiff and difficult to lift when the door is closed, the problem points to alignment. Adjusting the hinges or moving the keeps is a job a fitter or a locksmith does to put the door back into alignment.
A worn gearbox
The gearbox is the hardest working part of your door. It takes the physical force from the handle and uses it to drive the locking points up and down the edge of the door. Over years of daily use, the internal metal cogs and springs suffer from normal wear, and a dry mechanism will wear out even faster.
When the gearbox starts to fail, the symptoms are different to a dropped door. If the handle feels stiff, gritty or floppy even when the door is wide open, this points to a problem inside the gearbox, which a fitter should confirm. The resistance is happening inside the mechanism, not between the door and the frame.
If the handle is completely loose and spins without moving the locking points, the gearbox has probably already failed. If the door is stuck locked, do not force it and call a locksmith.
A failing cylinder
Sometimes the multipoint locking strip and the gearbox are perfectly fine, but the euro cylinder is failing. The cylinder contains small metal pins and springs that must line up exactly for the key to turn.
As the Master Locksmiths Association explains, a failing euro cylinder may stop the key from going fully into the lock. If the key will not go all the way in, you cannot turn it, and you cannot lock or unlock the door. It is useful to know what causes a key to stick before you ask a professional to replace it.
If the key goes in but will not turn, and the handle will not pull down, this usually means the wider locking mechanism has broken rather than just the cylinder. If you have multiple doors that use the same key, known as keyed alike locks, a locksmith can supply a replacement cylinder to match your existing set so you do not need to carry extra keys.
Do not keep forcing the handle
Forcing the handle on a misaligned door is the main cause of gearbox failure. When the door drops and the locking points miss the keeps, the force you apply to the handle goes through the gearbox.
If you have to lean your body weight on the handle to lock the door at night, the door may need adjusting by a fitter or locksmith before the gearbox is damaged. If the gearbox fails completely and the door cannot be secured, the locksmith may have to resort to boarding up the property overnight to keep it safe until parts arrive.
If the door is already stuck locked, do not try to force it open. Pulling heavily on the handle or trying to pry the door away from the frame can damage the door. A locksmith can advise on the safest way to open it.
Repair or replace
When a locksmith arrives, they will diagnose exactly which part of the system has failed. You do not always need to buy a complete new locking system. In many cases, replacing a single component is enough.
If the handle is stiff or floppy even when the door is open, replacing only the gearbox is usually enough. The rest of your original locking strip can stay in place.
However, if a specific hook, roller or bolt on the metal strip is broken, you will need a full multipoint lock replacement.
This table matches common symptoms to the likely cause.
|
What you notice |
When it happens |
Likely cause |
|---|---|---|
|
Handle is stiff to lift |
Only when the door is shut |
Alignment problem (door has dropped) |
|
Handle is stiff or floppy |
Even when the door is open |
Gearbox is worn or failing |
|
Handle spins freely |
At all times |
Gearbox has probably failed |
|
Key will not go fully in |
At all times |
Euro cylinder may be failing |
These symptoms are strong clues, but a local locksmith will need to test the door to confirm the exact fault.
What the repair usually costs
Locksmiths usually price this kind of work as a labour charge plus the cost of any parts required. Some locksmiths charge a fixed price for the whole job, while others charge by the hour. It is important to ask whether the price they quote on the phone includes VAT, as this makes a significant difference to the final bill.
The time of day you call will also change the price. Evening, night, weekend and bank holiday call outs cost more than a standard weekday visit. If your lock is just a little stiff but still secures the house, it is often worth waiting until normal working hours to avoid paying a premium rate. There is no government licensing for locksmiths in the UK, so anyone can trade as one, making it essential to vet the business first.
The Master Locksmiths Association publishes 'from' prices for 2026 to help you understand what to expect. A uPVC door lock repair starts from £85.
This table shows the MLA's 2026 starting prices for replacement parts and repairs.
|
Type of repair or part |
Starting price (inc VAT) |
|---|---|
|
Door lock repair |
from £85 |
|
Replacement gearbox |
from £85 |
|
Standard euro cylinder |
from £105 |
|
Anti-snap euro cylinder |
from £137 |
|
Multipoint lock strip (part only, no labour) |
from £76 to £263+ |
These are MLA 2026 'from' prices, and local quotes will differ based on your area and the specific brand of lock your door requires.
The Master Locksmiths Association notes that replacing a gearbox may actually be cheaper than attempting a complex repair. If you need a completely new multipoint lock strip, the part alone can cost anywhere from £76 to over £263 before any labour is added. If your door is relatively new, it is worth checking whether it is still under the original installer's guarantee before you pay for a private repair.
Locks and security on a composite door
When replacing parts on a composite door, it is crucial to maintain its security rating. If your door was originally tested to the PAS 24 standard and carries a Secure by Design certificate, the lock has already been tested to a high level. In this case, the MLA says new locks are not needed.
If your door is untested or older, replacing the cylinder is an opportunity to improve your home security. The Master Locksmiths Association recommends fitting either a Sold Secure SS312 Diamond cylinder or a TS 007 three-star cylinder. These are snap-resistant standards, and you can easily learn how to check for anti-snap locks on your own doors.
Your home insurance policy may also dictate what standard of lock you must have. Insurers often ask what locks are fitted to your external doors, and if a lock does not work properly or does not meet their stated standard, your cover could be at risk. Always check your own policy wording to see what your insurer expects.
Common questions
Can a locksmith open a composite door with a broken mechanism?
A locksmith can normally open a composite door with a failed mechanism, and will aim to use non-destructive entry (picking or bypassing rather than drilling) where possible. You should not try to pry the door open yourself, as this will damage the frame.
Can an auto locksmith fix my front door?
No, auto locksmiths are a separate specialism covering vehicle entry, key cutting, transponder and remote programming. To fix a composite front door, you need a standard domestic locksmith.
How long does it take to fix a composite door lock?
Most single lock changes and lockout situations take well under an hour to resolve. If the locksmith needs to replace a full multipoint locking strip, it may take longer.
Do I have to pay if the locksmith does a bad job?
Under the Consumer Rights Act 2015, any service you pay for must be carried out with reasonable care and skill, and within a reasonable time. If no price was agreed upfront, you only have to pay a reasonable price. If the work is poor, you have a legal right to ask the tradesperson to put it right, or to ask for some or all of your money back.
Can I cancel a locksmith if I change my mind?
Under the Consumer Contracts Regulations 2013, you normally have a 14-day cancellation period for services arranged at home or over the phone. However, this cooling-off period does not apply if you specifically asked the business to visit your home for urgent repairs. Any extra work they sell you during that visit that you did not originally ask for is not covered by this exception.
What to do next
If your composite door lock is stiff, floppy, or refusing to lock, take these steps to get it sorted safely:
- Test the handle with the door open and then shut to see if the problem is alignment or a failing gearbox.
- Check your paperwork to see if a recently fitted door is still under the installer's guarantee.
- Stop forcing the handle immediately to prevent the gearbox from snapping.
- Look for a local locksmith with a real local address and consistent customer reviews over time.
- Ask the locksmith for a total price before work starts, making sure it includes parts, labour, VAT, and any out-of-hours charges.
- Ask how they plan to gain entry if the door is stuck, and whether they expect to have to drill the lock.
- Ask what security standard any new cylinder will meet, checking your home insurance policy first to see what is required.
- Ask to see their identification when they arrive, and insist on a written invoice when the job is done.
Taking the time to check reviews and ask the right questions over the phone will help you avoid national call centres that pass jobs to whoever is nearest, or rogue traders who quote a low price on the phone that multiplies on the doorstep. When you are ready to get the door fixed, you can find a locksmith near you to diagnose the fault and get your home secure again.
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