uPVC door won't lock: causes and fixes

A uPVC door that will not lock is one of the most frequent daytime calls we take, and it tends to arrive with the same story: it has been getting stiffer for months, and tonight the handle will not lift at all. Most of these doors can be repaired rather than replaced, and the repair is quicker when the lock has not been forced. This guide helps you tell what is wrong and what to expect from us.

How a uPVC multipoint lock works

When you lift the handle on a uPVC door, a gearbox in the edge of the door drives a long strip with hooks, rollers or bolts along it into keeps on the frame. Turning the key then deadlocks the gearbox so the handle cannot be moved. For the whole thing to work, every hook and roller has to line up with its keep. A few millimetres out, and the handle will not lift, or lifts only with force.

Fault one: the door has dropped

Doors are heavy, and hinges settle. In warm weather uPVC also expands slightly. The result is that the door sits lower or tighter in the frame than it did when the keeps were set, and the locking points catch on the edges of the keeps rather than dropping into them.

You can usually tell an alignment problem because the handle lifts freely with the door open and stiffly with it closed. Sometimes lifting the door slightly by the handle as you lift the lever lets it lock. That is a temporary workaround, not a fix. The repair is to adjust the hinges to bring the door back into line and, if necessary, move or repack the keeps. It normally takes us well under an hour.

Fault two: the gearbox has failed

If the handle is floppy, spins without resistance, or lifts freely whether the door is open or closed but the door still will not lock, the gearbox itself has broken. Years of lifting a stiff handle against a misaligned door is the usual cause, which is why we say alignment problems should be dealt with early.

A failed gearbox cannot be adjusted. It has to be replaced, and there are dozens of patterns. We identify the make and size, and we carry the common ones. If the door is locked shut with a failed gearbox, we open it without damage where possible and replace the mechanism in the same visit.

Other things we find

A key that turns but does not throw the lock usually means the cylinder cam has failed, and the cylinder needs replacing. A handle that has become loose or sits at an angle is often just spindle wear or a broken spring cassette. A door that locks but whistles or lets in draughts has usually lost its compression and needs the keeps adjusted rather than anything replaced.

What not to do

Do not force the handle. A gearbox that is nearly failed will fail completely, and a door that was stiff becomes a door that is locked shut with you on the wrong side of it. Do not spray oil into the mechanism; it attracts grit and can gum the gearbox further. Do not try to adjust the hinges without knowing which screw does what, as some adjustments are one-way.

If the door has failed locked and you are outside, that is a lockout and our emergency locksmith can attend any hour via the emergency line.

What a repair involves

We start by checking the door with it open and closed to separate alignment from mechanism. Alignment work is hinge and keep adjustment, and we check the door still seals properly afterwards. Gearbox replacement means removing the handle and cylinder, sliding the strip out of the door edge, fitting the new mechanism and refitting. In both cases we lubricate the moving parts with a dry lubricant and check every locking point engages cleanly.

If you would like the cylinder upgraded to an anti-snap type while we are there, which we recommend on any uPVC door in Manchester, we can do that in the same visit.

Keeping it working

Once a year, with the door open, lift the handle and look at the strip. Wipe it clean and apply a light dry lubricant to the hooks and rollers. Check the door closes without you having to lift or push it. If it starts to need force, call us before it needs force it cannot take.