It’s late, you lift the handle to lock up, and it just won’t go. Or it goes halfway and stops. Or the key turns uselessly while the door stays unlocked.
A uPVC door that won’t lock is one of the most common calls we get in London, and the good news is that most of the time nothing is broken yet. Keep reading, because the one thing most people do next (forcing the handle) is what turns a free fix into a £150 repair.
The short answer
Open the door and try to lock it while it’s open. If it locks fine, the door has dropped or swollen and the hooks are missing the keeps in the frame: a hinge or keep adjustment usually fixes it. If it still won’t lock with the door open, the gearbox or multipoint mechanism inside the door has failed and needs replacing.
How a uPVC lock actually works
A uPVC door doesn’t have one lock. It has a long metal strip running down the edge of the door, called a multipoint mechanism, with hooks, rollers or bolts at three to five points. When you lift the handle, a gearbox in the middle drives all of those points into metal keeps screwed into the frame. Turning the key then locks the gearbox in place.
That design is very secure, but it means everything has to line up within a few millimetres. If the door sags, swells in the heat or a keep works loose, one hook catches on the frame and the whole thing jams.
The 60-second test that tells you what’s wrong
Before you touch a screwdriver, do this. It splits the problem in two and saves a lot of guessing.
Leave it wide open so nothing in the frame can get in the way.
Watch the edge of the door. All the hooks and bolts should shoot out smoothly.
The mechanism is fine. The problem is alignment between the door and the frame. Go to causes 1 to 4 below.
The problem is inside the door: gearbox, mechanism, handle or cylinder. Go to causes 5 to 7.
7 reasons your uPVC door won’t lock
1. The door has dropped on its hinges
This is the big one. uPVC doors are heavy, and over a few years the weight pulls the door down on its hinges. Look at the gap around the door: if it’s wider at the top on the handle side and tight at the bottom, the door has dropped. The hooks then hit the keeps too low and won’t engage.
Fix: most uPVC hinges have an Allen key adjustment for height and lateral movement. A few turns on the top hinge lifts the handle side back up. Small adjustments, test after each one.
2. Keeps in the frame are out of position
The keeps are the metal plates on the frame that the hooks lock into. They can work loose, or simply sit a few millimetres too far in or out. Look for shiny scuff marks on the keep or the frame: that’s where a hook is hitting instead of sliding in.
Fix: many keeps have adjustable inserts, or can be loosened and moved slightly. Tighten everything afterwards.
3. Heat has made the door swell
On hot days, especially on south-facing doors in direct sun, uPVC expands. A door that locks perfectly in the morning can refuse to lock by mid-afternoon. If the problem comes and goes with the weather, this is almost certainly it.
Fix: wait for the door to cool, or cool the frame with a cloth soaked in cold water. If it happens every summer, a small hinge or keep adjustment gives it the clearance it needs.
4. Weather seals or something in the frame
A seal that has come loose, a bunched-up draught excluder, or simply a doormat pushed against the bottom of the door can stop it closing those last few millimetres. Check along the full height of the frame.
5. The gearbox has failed
If the door won’t lock even when it’s open, the gearbox in the centre of the mechanism is the usual suspect. The handle may feel loose, floppy, or stop dead halfway up. Gearboxes wear out, and they break much faster when people force a handle on a door that’s out of line.
Fix: the gearbox, or sometimes the whole mechanism, needs replacing. It’s a job for a locksmith, because the part has to match your mechanism’s brand, backset and centres exactly.
6. The handle spring has gone
If the handle droops instead of springing back to horizontal, the spring inside the handle has failed. It can stop the mechanism engaging properly. Replacing the handle set is usually a quick, cheap fix.
7. The cylinder is worn or the key is bad
If the handle lifts fine but the key won’t turn to lock, the problem is the euro cylinder or the key. Copied keys cut slightly wrong are a common cause, so try the original key first. A worn or damaged cylinder just needs swapping, and it’s a good moment to upgrade to an anti-snap TS007 3-star cylinder.
What it costs to fix in London
Prices depend on the brand of mechanism and whether parts are in stock, but here’s what our customers typically pay for a daytime visit.
| Problem | Typical fix | Daytime price |
|---|---|---|
| Dropped door, loose keeps | Hinge and keep adjustment, lubrication | From £95 |
| Worn cylinder or bad key | New TS007 3-star euro cylinder | £90 to £120 |
| Floppy handle | New handle set | From £95 |
| Failed gearbox | Replacement gearbox | £140 to £190 |
| Failed multipoint mechanism | Full mechanism replacement | On quote, depends on brand |
Night and weekend visits cost more, and the full list is in our guide prices. If your door is still under the installer’s guarantee (often 10 years on the door, less on the hardware), call them first, because adjustments and some parts may be covered.
When to call a locksmith
Adjust the hinges yourself if you’re comfortable with an Allen key, but stop and call someone if the door won’t lock while it’s open, if the handle has gone floppy or stiff, or if you can’t secure the door overnight. A door that won’t lock is a door your insurer won’t cover, so it isn’t something to leave for a week. Our uPVC door lock repair vans carry the common gearboxes and mechanisms, so most jobs are finished in one visit.
Key takeaways
- Lock the door while it’s open: if it works, it’s alignment; if not, it’s the mechanism.
- Dropped hinges and misaligned keeps cause most uPVC locking problems, and both are adjustable.
- Never force the handle on a door that’s out of line. That’s how gearboxes break.
- A gearbox replacement in London typically costs £140 to £190 in the daytime.
- Check your door guarantee before paying for a repair.