Why Won't My uPVC Door Lock When It Is Closed?
For a uPVC entrance, back or patio-style door where the handle or key works differently once the door is shut, often because the locking points no longer line up with the frame.
What this usually means
If a uPVC door locks when open but will not lock when closed, the lock itself may be fine and the door may simply be out of alignment. A dropped sash, hinge movement, temperature expansion or misaligned keeps can stop the multipoint hooks and rollers entering the frame correctly. If the handle will not lift fully with the door shut but moves normally when the door is open, alignment is a strong clue. Do not force the handle or key because that can turn a simple adjustment problem into a broken gearbox.
What may be causing this
The door has dropped slightly on its hinges
Clues: The door catches the frame, needs lifting, or the handle is much harder to raise when the door is closed than when open.
What to do: The hinges or door alignment need adjustment so the multipoint locking points meet the keeps correctly.
The keeps in the frame no longer line up with the locking points
Clues: You can see rollers, hooks or the latch striking the edge of a keep rather than entering it.
What to do: The door or keeps need realignment. Avoid moving multiple keeps randomly because it can make the compression and security worse.
Temperature movement has made a marginal fit too tight
Clues: The problem is much worse during very hot or cold weather and improves when temperatures moderate.
What to do: Thermal movement can expose an existing alignment issue. Persistent problems still need adjustment rather than repeated force.
The lock mechanism or handle has developed a fault
Clues: The handle is stiff or fails even when the door is open, or the key will not operate the lock with the door open.
What to do: This points away from simple frame alignment and towards the handle, cylinder or multipoint gearbox itself.
How to check what is happening
The lock mechanism can operate, so alignment with the frame is the first suspect.
The door leaf has likely dropped or moved out of square.
The lock is being physically prevented from completing its travel.
Temperature expansion may be worsening a marginal alignment problem.
Can you fix this yourself?
Basic visual checks and some manufacturer-approved hinge adjustments can be DIY tasks if you understand the hinge type. If the external door cannot be secured, the gearbox is stiff even when open, or the door leaf needs supporting, use a locksmith or uPVC door specialist.
- Torch
- Allen keys only if specified for the fitted hinges
- Light machine oil or graphite only where the manufacturer recommends it
- Door care instructions if available
What you can safely try
- 1
Test the lock with the door open
Operate the handle and key gently while the door is open. If everything works normally, the frame alignment is more likely than an internal lock failure.
- 2
Find where the door is catching
Close the door slowly and look at the gaps around the frame. Note any corner that touches early or locking point that does not line up.
- 3
Do not force the handle or key
If the multipoint mechanism cannot enter its keeps, extra force can damage the gearbox or snap the key without correcting the alignment.
- 4
Check hinge adjustment only if the hinge type is clear
Some uPVC hinges have straightforward height and lateral adjustment. Follow the manufacturer method and make small changes rather than turning every adjustment at once.
- 5
Get help quickly if the door cannot be secured
A locksmith or uPVC repair specialist can align the door, adjust keeps and test the lock mechanism without automatically replacing the whole door.
Call a locksmith if…
- The external door cannot be locked securely.
- The handle or key is stiff even with the door open.
- The door leaf is visibly loose or sagging heavily.
- Adjustment would require removing or supporting the complete door.
- The key is bending or the gearbox feels close to breaking.
Get the right professional.
This problem can have more than one cause. Start with the checks above: a locksmith is the usual first route, while a window fitter may be more appropriate when the clues point that way.
Sources used for this guide
We prefer primary UK guidance, regulators and manufacturers for technical and safety-sensitive claims.
Last reviewed: 31 August 2026. Home Manual updates review dates only when the substance of a guide is checked or changed.