First, a simple test
Open the door and, with it open, lift the handle and turn the key. If everything works smoothly with the door open but not when it is closed, the lock is probably fine and the door is out of alignment. If it is stiff or won’t move even with the door open, the problem is inside the mechanism or the cylinder.
Common causes
- Door alignment: doors drop and frames move with temperature. In hot weather uPVC expands, so a door that locks in winter can stick in summer.
- Worn or misaligned keeps: the hooks and rollers catch on the keeps in the frame instead of sliding in.
- Failed gearbox: the central gearbox behind the handle wears out. A floppy handle, or one that won’t lift at all, is a classic sign.
- Faulty cylinder: the key is stiff, only turns part-way or won’t turn at all.
- Broken handle spring: the handle droops and doesn’t return to level.
Safe checks you can try
- Look along the frame for anything blocking the keeps, such as debris, paint or a bent keep.
- Push the door firmly closed against the seals while lifting the handle. If it then locks, alignment is the issue.
- Lubricate the moving parts on the edge of the door with a light lubricant, and use a dry PTFE or graphite spray in the keyhole rather than oil, which attracts dirt.
- Check the hinges for loose screws, or a door that has visibly dropped at the lock side.
What not to do
Don’t force the handle up or the key round. Extra force is the most common way a worn gearbox or cylinder breaks completely, and it can leave the door stuck locked, or impossible to lock overnight. If the door won’t lock at night, secure it with any additional bolt or lock you have and call for help.
When to call a locksmith
- The handle won’t lift, or lifts but nothing engages.
- The key won’t turn, or turns but the door stays unlocked.
- The door won’t open at all: a failed mechanism can trap the door shut.
- Your cylinder isn’t anti-snap. This is a good moment to upgrade to a TS007 3-star or Sold Secure Diamond cylinder.
A uPVC lock repair or opening is typically £69, and a door realignment £89-179. Replacement mechanisms vary by door, so the part and price are confirmed before fitting.
Common questions
Why does my uPVC door only stick in summer?
uPVC expands in heat, so the hooks and rollers stop lining up with the keeps. A small hinge and keep adjustment usually cures it for both summer and winter.
Do I need a whole new lock?
Often not. Alignment and keep adjustments fix many doors. A failed gearbox can sometimes be replaced on its own instead of the full multipoint mechanism, depending on the make.
Is my euro cylinder anti-snap?
Look on the face of the cylinder by the keyhole for a Kitemark with three stars (TS007 3-star) or a Sold Secure Diamond mark. If there is no marking, it is probably a standard cylinder and worth upgrading.