Why Your UPVC Lock Stops Working in Winter

Every January we get dozens of calls: "My door was fine yesterday, now the key won't turn." It's not your imagination — cold weather puts real stress on UPVC locks.

The Root Cause: Thermal Contraction

When temperature drops below 5°C, three things happen:

1. The PVC frame contracts by 2–3mm on a standard door
2. Metal mechanisms shrink at different rates
3. Any existing misalignment gets significantly worse

Parts that worked at 15°C can jam solid at 2°C.

"Key Won't Turn"

Your euro cylinder has 5–6 pins that need to align precisely. Cold metal contracts, making tight cylinders impossible to turn.

Quick fix: warm the key with a lighter for 5 seconds, insert gently, turn carefully. Works in about 80% of cases.

Don't force it — you'll snap the key inside the cylinder.

If warming the key stops working, the cylinder is worn and needs replacing.

"Handle Lifts But Won't Lock"

The door has contracted away from the frame. The multi-point hooks now miss their keeps by 1–2mm.

Immediate fix: push the door firmly into the frame while lifting the handle. It should click into position.

Permanent fix: hinge adjustment. A locksmith can do this in around 15 minutes.

Prevention

Lubrication works only if done correctly:

• Use graphite powder, not WD-40
• Apply in October or November, before cold weather arrives
• Cover the cylinder and all moving parts
• Repeat every 6 months

When to Call Someone

• Key has snapped in the lock
• Handle has completely detached
• Door won't close at all
• You've forced it and made things worse

Need urgent help? Call: 020 3051 8388