Most faults on uPVC and composite doors are repairable: sticking or failed multi-point locks, snapped cylinders, loose handles, dropped doors, worn hinges, draughty seals and misted glass panels. A new door is only needed when the frame or slab is damaged, badly warped, or you want a different door. Knowing which part has failed saves you paying for more than you need.
This page lists the common faults and the repair behind each. For help deciding between repair and a new door, see our door repair or replace guide.
Lock and handle faults
Multi-point lock mechanism
If the handle is stiff to lift or won't lock, the hooks and rollers may be misaligned or the gearbox inside the door may be failing. Realignment fixes the first; a replacement mechanism of the same type fixes the second.
Cylinder (barrel)
Keys that stick, snap or turn uselessly usually mean a worn cylinder. Upgrading to an anti-snap cylinder at the same time is sensible.
Handles
Handles loosen, droop or crack. They are swapped for the correct centres and fixing type.
Door hanging and closing
Doors drop on their hinges over time so they catch the frame or the lock won't line up. Most uPVC door hinges have adjustment for height, side and compression; worn hinges can be replaced. A door that's hard to close may simply need the keeps moving.
Draughts, glass and fittings
- Worn or shrunken weather seals replaced
- Misted or cracked glass panels replaced with new sealed units
- Letterplates, knockers and door chains replaced or fitted
- Thresholds and drainage checked where water gets in
Describing the fault when you call
A quick description speeds things up: whether the door is uPVC or composite, what the handle and key do when you try to lock it, whether the door catches at the top or bottom, and roughly how old it is. A photo of the edge of the door showing the lock faceplate helps identify the mechanism, because there are many different lock types and matching the right one is most of the job.
If the door won't lock at all, keep it secure in the meantime and avoid forcing the handle, which can snap the gearbox and make the repair bigger.
When repair isn't the answer
If the frame is cracked, the door slab is warped or delaminated, the door is badly insecure, or repeated repairs keep failing, a new door is usually better value. We fit uPVC and composite doors made to measure, and we'll tell you honestly whether repair or replacement suits your door after looking at it.
Common questions
Usually yes, by adjusting or replacing the hinges and resetting the keeps.
If the door and frame are sound, a replacement lock mechanism or cylinder is far cheaper than a new door.
Yes. The glass panel is a sealed unit and can be replaced on its own.
Call 07538 882579 or use the contact form and describe the fault.
Want a straight answer on your own windows or doors?
DM Installations fits and repairs windows and doors across Central Scotland — Cumbernauld, Glasgow, Falkirk, Stirling and the surrounding towns. Free survey, written quote, and an honest answer on whether you need a repair or a replacement.
Related guides
Door Repair or Replacement: How to Decide
A symptom-by-symptom way to judge whether your door is worth saving, and what a replacement actually solves.
How-toHow to Adjust a uPVC Door
Which screw does what on flag, butt and rebate hinges, and how to get a dropped or sticking door closing properly again.
When to call a proDoor Lock and Security Problems
Failing gearboxes, snappable cylinders and the cheap upgrades that make the biggest difference to door security.