It’s a classic. The first proper warm spell of the year arrives, and suddenly your front or back door won’t lock. You lift the handle and it won’t go up, or it goes halfway and jams, or the whole door feels like it’s fighting you. Come the cool of the evening it works perfectly again, so you tell yourself you imagined it. Then it happens again the next hot afternoon.
You’re not imagining it, and there’s nothing wrong with you. Heat and uPVC doors just don’t get along, and it’s one of the most common summer callouts we get around Wishaw. Most of the time it’s fixable, and quite often you can sort it yourself in a couple of minutes. Here’s what’s happening and what to try.
Why heat stops the door locking
uPVC expands when it warms up. It’s a plastic, and on a hot day a door that fits snugly in winter can grow just enough to catch against the frame. When that happens, the locking points on the edge of the door (the hooks and rollers of the multipoint mechanism) no longer line up with the keeps they’re supposed to slot into on the frame. You lift the handle to throw those bolts, they hit metal instead of the gap they need, and the handle won’t complete its travel.
South and west-facing doors get the worst of it because they take the full afternoon sun. A dark-coloured door is worse again, since darker plastic soaks up more heat. None of this means the door is broken. It’s just moved a whisker out of alignment because it’s warm.
Try this first, before you call anyone
Nine times out of ten one of these gets you locked up:
- Lift and lean. Pull the door firmly towards you by the handle (or give it a gentle shoulder if it opens outwards away from you), so you’re pushing it back into proper alignment with the frame, and try lifting the handle at the same time. Getting the door central in its frame is often all it needs.
- Lift, don’t force. If the handle won’t lift, never wrench it. The plastic handle can snap and then you’ve a second problem. Ease it up gently while jiggling the door.
- Cool it down. If it’s a mechanism that only sticks in the heat, cooling the door edge can shrink it back enough to lock. A cloth soaked in cold water run along the frame edge sounds daft, but it buys you the locking you need on a scorcher.
- Check for the obvious. Make sure nothing’s fouling the bottom of the door: a dragging draught excluder, grit in the threshold, a mat pushed underneath.
If the door locks once you’ve nudged it into place, the underlying issue is alignment, and that’s a proper fix rather than a nightly wrestling match. The hinges can be adjusted and the keeps repositioned so the door sits right whatever the weather.
When it’s more than the heat
There’s an important difference between a door that’s stiff and a door whose mechanism has actually failed, and it’s worth knowing which you’ve got.
If the handle lifts freely but the door won’t stay locked, or the key spins round and round without engaging anything, the multipoint gearbox inside the door has likely packed in. That’s the part that drives all the locking points at once, and when it goes the door often can’t be locked at all, which is a security problem rather than just an annoyance. Don’t leave it. A failed gearbox can usually be replaced without touching the rest of the door, and it’s a lot cheaper than a new door.
Likewise, if the handle has gone floppy, or the key is getting harder and harder to turn over weeks rather than just on hot days, the cylinder or the mechanism is wearing out and will eventually leave you locked out (or unable to lock up). Better to catch it before it strands you on the doorstep.
A quick word on security
While we’re on the subject, if your door still has its original barrel from years back, it’s worth asking about an anti-snap cylinder. A lot of older uPVC doors were fitted with cylinders that can be snapped in seconds by anyone who knows the trick, and upgrading to a proper anti-snap one is an inexpensive job that makes a real difference to how secure your home is. Worth doing at the same time as any lock work.
Getting it looked at
A sticking or unlocking door is exactly the sort of thing we sort day in, day out. Hinge adjustments, new keeps, replacement gearboxes and cylinders, all done on your existing door with no need to replace it. We cover Wishaw and right across Lanarkshire, there’s no call-out charge, and if you’re not sure how serious it is, take a photo or a quick video of the door doing its thing and send it over on WhatsApp. We’ll tell you honestly whether it’s a two-minute adjustment or a part that needs replacing.
Give us a ring on 01698 604 278 and we’ll get you locking up properly again.
If it keeps happening once the weather cools down, the door needs adjusting properly, and that is a simple door repair.
Related advice
See our door repair service page for what we do and where. You can also message us here.
You will find around fifty more guides like this one in our advice section.
Written by the team at Wishaw Window Repairs. Over thirty years repairing uPVC windows and doors across Lanarkshire.