Overview
Composite door 'lock' usually means one of two things: the cylinder (the barrel your key goes into) or the multi-point mechanism (the strip down the door edge with hooks and bolts). Both are replaceable, and both take under 90 minutes for an experienced installer.
Symptoms
- Lock has failed completely.
- Key snapped, lost or copied by someone you no longer trust.
- Moving into a new house - always change the cylinder.
- Insurance requires a 3-star anti-snap upgrade.
Common causes
- Age and wear - most gearboxes last 8-15 years.
- Water ingress corroding internals (coastal Cornwall properties in particular).
- Forced entry attempt.
- Original spec was low quality.
When to call a professional
- Always - multi-point mechanisms are handed, sized and brand-specific. Getting the wrong part is expensive.
Prevention
- Service the mechanism every 2 years.
- Upgrade to a 3-star cylinder proactively - cheap insurance.
- Keep drainage slots at the bottom of the door clear.