How to Fix Common UPVC & Composite Door Lock Problems (Step-by-Step)

UPVC and composite doors are known for their durability and security, but like any mechanical system, they can develop issues over time. If your handle feels stiff, the key doesn’t turn properly, or the door won’t close as it should, this guide explains what to check before calling a locksmith.

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Step 1 – Check Door Alignment

Door alignment problems are the most common reason a UPVC lock stops working.

Close the door slowly and check if the latch meets the strike plate cleanly.

If it catches or scrapes, the hinges may have dropped or expanded due to heat.

Slightly adjust the hinge screws or lift the door gently while turning the handle.

If the handle movement improves, misalignment was the cause.

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Step 2 – Inspect the Multipoint Locking Strip

Your UPVC or composite door has a multipoint locking strip running along the edge.

Open the door and pull the handle to see if all hooks or bolts move freely.

If one part doesn’t move, the gearbox could be worn or jammed.

Lubricate the mechanism lightly with graphite or silicone spray (avoid WD-40).

If lubrication doesn’t fix the issue, a new gearbox may be required.

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Step 3 – Test the Cylinder

If the key feels loose, stiff, or doesn’t turn:

Remove the fixing screw on the edge of the door.

Slide the cylinder out carefully and inspect the cam.

Replace it with a British Standard anti-snap euro cylinder if worn or damaged.

Upgrading to a 3-Star Ultion or ABS cylinder is a good idea for extra protection and insurance approval.

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Step 4 – When to Call a Professional Locksmith

Call a professional locksmith if:

The key is stuck or broken in the lock

The door is locked shut

The gearbox is completely jammed

Forcing a jammed multipoint system can cause further damage and turn a £120 repair into a £250 replacement.

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Need Help Fast?

http://www.amzlocksmith.co.ukprovides expert UPVC and composite door lock repairs across West and North-West London, including Acton, Harlesden, Willesden, Wembley, Chiswick, Maida Vale, and Shepherd’s Bush.

Call 07484 839662 for 24-hour service.

No call-out fee within 5 miles.

DBS-checked, UKLA member, and fully insured.