Guide
uPVC Door Will Not Lock Tonight? How to Tell Which Fault It Is
Your uPVC door closes, but when you lift the handle to lock it, it stops, sticks or will not go. Before anything else, try this: lift the handle with the door standing open, then try again with it shut. The difference between those two attempts usually names the fault.
A door that locks while open but not while shut is almost always an alignment problem. A handle that will not lift in either position points to the mechanism inside the door. And a door that began playing up during a heatwave or a cold snap may need nothing doing to it at all. This guide from Runcorn Locksmith walks through each case, shows what you can safely adjust, and explains what not to do while you wait. If the door cannot be secured tonight, call 01928 611001; emergency calls are answered 24 hours a day, every day of the year.
Call with your postcode for a current arrival estimate.
- 24-hour emergency cover
- No call-out charge
- Price agreed before work starts
Start With the Open Door Test
Open the door wide, lift the handle, and watch the hooks and rollers along the edge. If the handle rises and the hooks throw out with the door open, the mechanism works and the problem lies where the door meets the frame. If the handle will not lift even with the door open, the frame has nothing to do with it. Either way, if the handle does not lift easily, that is your result; do not push harder.
| What you observe | What it means | What to read next |
|---|---|---|
| Handle lifts freely with the door open, stiffens or stops when shut | The locking points are not meeting the keeps on the frame | The alignment section below |
| Handle will not lift, or lifts and achieves nothing, even with the door open | The fault is inside the door, usually the gearbox | The gearbox section below |
| The door will not open at all | A separate problem with its own diagnosis | A uPVC door that will not open |
Door misalignment, a failing mechanism and temperature change are the three usual causes, and this one test sorts between them before anyone buys a part or books a visit.
The Handle Lifts With the Door Open but Not When It Is Shut
The mechanism is working, and the door no longer lines up with the frame. When you lift the handle, hooks and rollers swing out from the door edge and have to enter the keeps on the frame. If the door has dropped, swollen or shifted, one or more of those hooks hits metal instead of the slot, and the handle stops part way.
What turns a guess into an observation is the evidence the hooks leave behind. Look for:
- A bright rubbed mark or shiny patch on one of the keeps, which shows where a hook is catching.
- Gaps around the door that are wider at one corner than another.
- Resistance or rubbing as the door closes.
These signs suggest the door needs adjusting rather than a new lock, although an underlying mechanism fault cannot be ruled out without an inspection. The order of work, set out below, is to move the keep that is catching before touching any hinge.
The Handle Will Not Lift in Either Position
Here the frame plays no part, so the problem sits inside the door. With the door wide open there is nothing for a hook to catch on, so a handle that still will not lift is being stopped by the mechanism itself, most often the gearbox at its centre. Two versions of this sound alike but are different jobs:
- The handle lifts part way and stops hard. Something inside is jammed or worn, and it may be an adjustment or a repair.
- The handle lifts with no resistance and nothing moves. Something inside has usually sheared, and the handle is no longer connected to anything.
Our guide to what goes wrong inside a uPVC lock mechanism covers both in full. The one thing that makes either worse is forcing it, which has a section of its own further down.
If It Began in a Heatwave or a Cold Snap
If the door locked perfectly last month and stopped during a hot spell, it may not have a fault at all. The pattern is recognisable: the door is worse in the afternoon than in the morning, worse on a sunny side of the house than on a shaded one, and it recovers by itself when the weather changes. uPVC expands as it warms and shrinks as it cools, and even a small shift in the door or frame changes how the hooks, rollers and bolts meet their keeps.
How Far a uPVC Door Actually Moves
uPVC moves by roughly 1.2mm per metre for every 20 degree change in temperature. Tangram Technology gives the coefficient of linear thermal expansion for PVC-U as 0.00006 per degree Celsius, and its worked example takes a 1,000mm length through a 20 degree rise to arrive at 1.2mm. Applying that coefficient to a door leaf around 2m tall gives movement in the order of 2.4mm over the same swing; that door figure is our arithmetic from Tangram's coefficient, not a number Tangram published about doors.
| Material | Movement on 1,000mm over 20 degrees |
|---|---|
| PVC-U | 1.2mm (Tangram's worked example) |
| Aluminium | about 0.5mm (worked from Tangram's ratio of about 2.5 times) |
| Mild steel | about 0.25mm (worked from Tangram's ratio of about 5 times) |
Tangram puts PVC-U at around five times the thermal expansion of steel and two and a half times that of aluminium. The reasoning for why doors in particular are affected runs like this: the frame is held in place by the wall around it and the leaf is not, and a leaf in direct sun runs warmer than a shaded frame. It is the difference between the two, rather than the air temperature by itself, that pushes the hooks off their keeps.
Why Adjusting a Hot Door Creates a Winter Problem
Set the two figures side by side: a 2m leaf moves in the order of 2.4mm across a 20 degree swing, while the compression adjustment on a flag hinge offers about 2mm in total, according to the Double Glazing Cost Calculator adjustment guide. The setting that decides whether the hooks reach their keeps has less travel than the seasonal movement. A door wound in to lock at 30 degrees can be tight, or worse, at 5 degrees, and you are back in the autumn with the opposite complaint. Add Premier Windows' point that the profile returns to size below 23 degrees, and the case for waiting becomes clear.
In a hot spell:
- Try the door again in the evening, once it has cooled.
- Compare it with any door on the shaded side of the house, and treat it as a fault only if it still will not lock after the weather has turned.
This is a reason to wait, not a claim that adjustment never helps. Meanwhile, do not assume a door held only by its latch is secure, because the latch can keep it closed without the multipoint locks engaging; if it cannot be locked properly, get help promptly. A door that has never locked well, or fails in every season, has a real alignment fault and belongs in the next section. If the cylinder itself is the issue, see changing the cylinder on a uPVC door.
Premier Windows, an installer, says uPVC frames may expand slightly above about 25 degrees and contract back to their original size once the temperature falls below 23 degrees. It adds that darker finishes such as anthracite grey and black expand more noticeably because they absorb more heat. Treat those thresholds as that installer's guidance rather than a standard. A door that stays hard to lock whatever the weather is more likely to have a genuine alignment or mechanism fault.
Adjust the Keeps Before You Touch the Hinges
If one hook is catching one keep, move that keep. A hinge moves the entire door, while a keep moves only the part that is wrong. The keeps are the metal plates on the frame that receive the hooks, rollers or bolts, and they are fixed through slotted screw holes. The Double Glazing Cost Calculator adjustment guide describes the method: loosen the screws, slide the keep two or three millimetres in the direction it needs to go, and tighten again. Draw round its original position in pencil first so it can always go back.
What Each Hinge Type Can Correct, and by How Much
The answer depends on which of three hinge types the door has, and you can tell by looking. Flag hinges are the most common and adjust in three directions: height by about 4mm of travel, sideways by about 5mm each way, and compression by about 2mm, usually with a 5mm allen key and occasionally a 4mm. Butt hinges, found on older doors, give up to about 2mm sideways through two Phillips screws and height through an allen screw beneath the top cap, though some cannot be adjusted at all. T-hinges, used on heavier doors, give height and lateral movement only, often by loosening the fixing screw and repositioning, and compression is seldom available.
The consequence: if the door needs more movement than its hinge type offers, no amount of turning will fix it, and the fault lies somewhere else. Where a lock suddenly stops working, a jammed mechanism, a shifted door or a damaged part are all possible, so repeat the open and shut handle test to narrow it down.
How Far to Turn Anything Before Testing
Turn a quarter to half a turn, then close the door and try it, every time. The Double Glazing Cost Calculator guide gives these limits:
- On height, a quarter to half a turn at a time.
- On compression, no more than 45 degrees at a time.
- A test between every adjustment, rather than several turns on one hinge.
The point people miss is that height is adjusted across all three hinges together, not one at a time; winding a single hinge up twists the leaf rather than lifting it. Then the stop rule. If two rounds of small adjustments have made no difference, stop and write down exactly what you changed, because whoever looks at the door next needs to know where it started. Stopping there is sensible, not a failure. Our guide to what lock and door work costs in Runcorn explains what affects the bill if you hand it on.
The distinction that decides the job is simple. One hook missing its keep is a keep adjustment; several hooks missing together means the whole door has moved, and that is a hinge adjustment. Before you change anything, look for loose fittings, rub marks and uneven gaps, because adjusting without a likely cause can make the door harder to close or secure. Never drill, file or enlarge a keep.
| Hinge type | What it adjusts | How much (approximate) | Tool |
|---|---|---|---|
| Flag hinge | Height, lateral and compression | Height about 4mm; lateral about 5mm each way; compression about 2mm | Usually a 5mm allen key, sometimes 4mm |
| Butt hinge | Sideways and height, where adjustable | Up to about 2mm sideways | Two Phillips screws for sideways; an allen screw under the top cap for height |
| T-hinge | Height and lateral; compression rarely | Not given as a figure; often repositioned at the fixing screw | Not specified by the source |
Figures are those of the Double Glazing Cost Calculator guide, not manufacturer specifications. If adjustment does not settle it, our lock repair service is the next step.
When It Is the Gearbox Rather Than the Alignment
The gearbox is the small unit in the middle of the metal strip in the door edge, and both the handle and the key drive it. It passes movement from them to the hooks, rollers or bolts, it takes the load of every lift of the handle, and it is the part that wears. When it fails, the handle either jams part way or goes slack.
- What happens next: on many doors the gearbox alone can be replaced, while on others the whole strip has to come out. Which applies depends on the mechanism fitted, not on how serious the fault feels.
- What decides the wait: the mechanism has to be identified and matched before anything is fitted, so it is a measuring exercise first. [CLIENT TO CONFIRM: whether mechanisms and gearboxes are carried as van stock]
Signs that point here rather than at alignment include a handle that jams, feels unusually loose, or fails to move the locking points even with the door open. Our guide to uPVC lock mechanism problems goes into each one.
Do Not Force the Handle
Forcing a handle against a jammed hook turns a small job into a large one. The handle is a lever, and the gearbox is the weakest link in the path that force takes. Push hard on a handle whose hooks cannot enter their keeps and the effort goes into the gearbox rather than the door, and a gearbox that worked before the push may not work after it. Parts that only needed adjusting, or a small repair, can end up needing replacement.
The same mistake has a second form: turning the key harder when it will not turn. That puts the strain through the cam and the cylinder, and can bend the key or snap it inside the lock.
- Do not lean on, kick or lift the handle with extra force.
- Do not turn a stiff key harder or use anything to add leverage.
- Do not keep slamming the door into position to make it lock.
Instead, stop, note what the door was doing, and leave it in whichever state is safest.
How to Leave the Door Secure Until It Is Fixed
There are two quite different situations: a door that closes and latches but will not throw its hooks is shut, while a door that will not close at all is open. Most people reading this have a door in one of those states and need to know what to do tonight.
Check:
- Whether the key still locks the door once it is pulled to. On some doors the cylinder throws a bolt independently of the hooks, so the door can be locked even though the handle will not lift fully.
- Whether any second lock on the door still works.
Do not:
- Wedge, tie or prop the door as a substitute for a lock.
- Leave a key in the inside of the cylinder.
- Leave a thumbturn or key reachable from a glazed panel.
A locksmith can often get a door locking during the visit even when the full repair has to wait for a part. [CLIENT TO CONFIRM: whether temporary securing with a return visit is offered] A door that cannot be made secure at all is an emergency, not a job for next week: see our 24 hour emergency locksmith page, or emergency boarding up after damage if the door or frame is broken.
Get the Fault Diagnosed
Tell us what the handle did with the door open and what it did with the door shut, and we can usually name the likely fault before anyone arrives. If a keep screw sorted it, all the better.
Have ready: the two test results, the door material, whether the problem started in a hot or cold spell, and a photograph of the door edge with the handle lifted.
There is no call-out charge at any hour, and emergency calls are taken 24 hours a day, every day of the year. Technicians are [PROVIDER PACK: DBS check confirmation] and the business holds [PROVIDER PACK: public liability insurance details]. You are given a price on the call from what you describe, and if anything found on site would change it, you hear before work begins.
Describe the Fault and Get a Price: call 01928 611001.
uPVC Door Locking Questions
If the door is shut but will not lock, is it secure?
You should not assume so. The latch can hold the door closed without the multipoint locking system engaging. If the door cannot be locked properly, arrange help promptly.
Does a uPVC door that will not lock need replacing?
Not necessarily. The cause may be alignment, a faulty cylinder or part of the multipoint mechanism, and these can often be repaired without replacing the whole door.
How can I tell if the gearbox is faulty?
Suspect the gearbox or mechanism if the handle jams, feels unusually loose or fails to work the locking points even with the door open. Those signs suggest an internal problem rather than the door rubbing on the frame.
Why does my door lock in the morning but not in the afternoon?
Heat is the likely reason. uPVC expands slightly as it warms, which can shift the locking points against the frame keeps, especially on a darker door in direct sun. If it returns to normal when the weather cools, it may not need adjusting.
Should I lubricate a stiff uPVC lock?
Only if the stiffness comes from friction and the manufacturer recommends lubrication, and only with a product approved for that particular lock. Lubricant will not correct a door that is out of line.
I rent my home. Who should fix a door that will not lock?
Usually the landlord, where the property is in England, unless the tenant caused the damage. Report the fault promptly, and make clear if the property cannot be secured.