Composite doors and uPVC doors look solid. They’re meant to last. But they both have weak points, and when they go wrong, people ring us day or night. Here’s what actually happens inside them, what you can do about it, and when we need to get involved.
The short answer
Composite doors are GRP over a timber or foam core, and uPVC doors are welded plastic, but both rely on a multipoint lock worked by the handle. When they go wrong it’s usually that mechanism or the door’s alignment, and most faults are fixed without a new door.
What’s actually going on inside these doors
A composite door is mostly GRP (that’s glass-reinforced plastic) wrapped around a timber or foam core. uPVC is hollow chambers of plastic welded together. Both have multipoint locks, usually operated by a handle lever or key. The difference matters because they fail in different ways.
In a composite door, the frame and door itself are rigid. When the lock mechanism inside binds up or the hinges drop slightly, the whole thing seizes. With uPVC, the plastic can warp or shrink in heat or cold, which pulls the door out of square. That means the locking points no longer line up. You turn the handle and nothing catches.
Both can also suffer from a worn lock barrel, a broken internal cam, or a snapped pin inside the multipoint lock unit. None of this is visible from outside.
What to do, and what not to do
First: don’t force it. If your door won’t lock smoothly, forcing the handle or the key will snap the internal cam or the spindle that joins the lock barrel to the handle. That’s a bigger job for us and costs more to sort.
Do this instead. Check the door frame is tight and level. Look for daylight gaps between the frame and the door. If there is one, the hinges may have dropped. Try lubricating the lock barrel with a tiny bit of graphite powder (not oil or WD40 – they gum up). Turn the key or handle slowly.
If it still won’t move, stop. Ring us.
How we sort it on the day
We arrive with non-destructive entry tools and the lock components to hand. We don’t drill unless we have to. First we’ll establish whether the issue is mechanical (the lock itself) or structural (the door frame). We check for alignment, hinges, and the state of the multipoint lock unit. Once we know what’s wrong, we’ll give you a straight quote. Sometimes it’s a clean extraction and replacement of the lock. Sometimes we adjust the frame or hinges. It’s honest work, no VAT, no call-out fee.
When to call us
Call straight away if your composite or uPVC door won’t lock at all, or if the key turns but nothing catches. Don’t leave it. A faulty lock is an open door to a break-in, and it voids many insurance policies. We cover Southampton, the Waterside, Totton, Eastleigh, Romsey and beyond in Hampshire. We’re here day or night.
If you’ve got a uPVC door that’s hard to lock but not seized, read our post on uPVC door lock repair – there are a few things to try first.
FAQ
More from Keywise: uPVC door repair.
