Stiff Lock in Winter | The Myth That It's the Lock, and What's Really Going On

Every January the "my lock's gone funny" calls roughly double, and most people ring convinced the lock has broken. Here's the myth worth busting before you spend money on the wrong thing: a stiff winter lock is usually not a broken lock at all.

The myth

It's cold, the door won't lock smoothly, so the lock must be failing. Squirt some WD-40 in, give the key a firm turn, and if it's really bad, pour a kettle over it. All three of those instincts are wrong, and two of them make it worse.

The reality: it's usually the door

uPVC and composite doors shrink a little in the cold. When the slab pulls in, the multipoint hooks stop lining up with the keeps in the frame, and locking gets stiff. The tells are obvious once you know them: fine in autumn, awkward by December, worse below freezing, easier when it warms, and often one point (usually the top hook) fighting more than the rest.

That's not a lock fault. It's alignment. We move the keeps and hinges a millimetre or two, 15 to 30 minutes, and the cold-weather sulk disappears for good. Cheap visit, sorted for the winter.

The second most common cause is a gummed-up cylinder, and that's where the WD-40 myth bites. Oil frees it for a week, then the residue grabs every bit of grit and the lock seizes harder than before. The fix isn't more oil, it's the right stuff: dry graphite or a PTFE lock spray, ten minutes, transformed.

What not to do

• Don't force a cold key. If it resists, stop. Forcing bends brass, and bent keys snap off in the cylinder. I extract enough of those every winter.
• Don't drown it in WD-40. Dry lube only.
• Don't pour boiling water on it. You'll warp the slab and the water refreezes inside. Warm the key in your hand instead, or use a lock de-icer if it's genuinely iced, which is rare around here.

When it's actually the lock

If the door fits fine cold, the cylinder's clean, and the key still turns reluctantly, then fair enough, the cylinder may be worn out. Brass and pins wear after 10 to 20 years. A wiggle in the key, a "knack" you've developed, or roughness even after lubricating, those point to a replacement, ideally a TS007 3-star anti-snap while it's out, £95-£160 fitted.

The cheap way to skip all this

Catch it in October. A quick lock health-check, lubrication with the right product, an alignment tweak and a look over the cylinders, hinges and gearbox, heads off most of the winter call-outs before they happen. If your door's stiff right now and you're not sure which of the three it is, ring the office and we'll diagnose at the door across RG21 to RG29, quote on the call, no surprises.