Door Lock Not Working? The Top 3 Problems and How to Solve Them

A lock that refuses to cooperate is more than an inconvenience — it can leave you locked out of your home or unable to secure it properly overnight. This guide works through the three faults that account for the vast majority of lock problems: a stiff or hard-to-turn cylinder, a key that turns but the door stays shut, and a key that has snapped inside the barrel. Each has distinct causes and, in many cases, a practical fix you can try before calling anyone out.

Problem 1: The Lock Is Stiff or Hard to Turn

A lock requiring real effort to turn is usually pointing to one of three things: the cylinder is dry, the mechanism is misaligned, or the key has worn down enough that it is no longer engaging the pins cleanly.

Cause 1: A Dry Cylinder

Lock cylinders need lubrication to function properly. Over time, especially in older uPVC doors or locks exposed to weather, the internal mechanism dries out. The correct fix is a graphite-based lubricant in spray or powder form, applied directly into the keyhole. Do not use WD-40 or general-purpose oil — these products attract dust and grit over time, and the cylinder will be in worse condition within a few months than it was before treatment. Dry graphite lubricant or dedicated lock lubricant spray costs around £4 to £6 from most hardware shops.

Cause 2: Door or Frame Misalignment

Doors shift with temperature and humidity. A timber door swells in damp weather; a uPVC door may drop slightly over years of use. When the door leaf no longer sits correctly in the frame, the latch or bolt has to fight the strike plate to engage, putting strain on the cylinder every time you turn the key. Check whether your door sits flush in the frame when closed. If there is a visible gap, or if the door requires a push or lift to lock, the hinges may need adjustment or the strike plate may need repositioning. On a standard single-leaf door, moving the strike plate by 1 to 2mm can make a significant difference.

Cause 3: A Worn Key or Cylinder

Keys are made from soft brass or nickel silver alloy. After years of use, the cut profile becomes slightly rounded, reducing the precision with which it lifts the cylinder pins. A worn key may still function in a new cylinder but will struggle in one that has also seen heavy use. The solution is to have the lock re-keyed or the cylinder replaced. A quality replacement euro cylinder meeting the TS007 3-star standard typically costs between £20 and £60 for the part, plus fitting.

Problem 2: The Key Turns but the Door Will Not Open

This is arguably the most frustrating fault — the cylinder is clearly working, the key turns fully, but nothing happens and the door stays shut.

Latch or Bolt Stuck Against the Strike Plate

The most common cause is a latch or bolt that is not retracting fully. On a standard rim lock or mortice lock, this usually means the mechanism inside the lock case has worn, or a spring has weakened. Open the door from the inside if you can and watch what the bolt does when you turn the key. If it moves only partway, the lock case likely needs replacing. If the bolt retracts but does not clear the strike plate opening, the plate itself has shifted — this is common on uPVC doors where the plastic frame has slightly deformed. Re-setting the strike plate is typically a 20-minute job for a locksmith.

Multi-Point Locking System Failure

Multi-point locking is standard on uPVC and composite doors. When you lift the handle and turn the key, a series of hooks, bolts and rollers engage simultaneously at several points around the frame. If any one of these fails, the door can feel completely stuck even though the cylinder is fine. Common failures include a broken gearbox inside the door or a hook that has bent slightly and is catching on the keep plate. Replacement of the multi-point mechanism is usually the right call — expect to pay £80 to £150 for parts and labour on a standard uPVC door. Our emergency locksmith service covers this across South London, usually on the same day.

Problem 3: The Key Has Broken Inside the Lock

A snapped key is a situation where the wrong response makes everything significantly worse. If the break has left a small section of key protruding from the cylinder, do not grab it with pliers and pull hard — this can push the broken section further into the barrel and complicate what would otherwise be a straightforward extraction.

What Not to Do

• Do not use superglue to re-attach the broken piece and pull it out. This either fails to bond or glues the cylinder itself, turning a £60 extraction into a £150 replacement.
• Do not use WD-40. The broken key will not float out, and the lubricant makes it harder to grip later.
• Do not push the broken section further in using a pin or screwdriver — this jams it deeper and makes extraction more difficult.

Professional Extraction

A locksmith uses a broken key extractor — a small hooked or barbed tool that catches the key's cuts and draws it back out of the barrel. In most cases, extraction takes five to fifteen minutes. The cylinder can then be assessed. If undamaged, you need only a new key cut. If the snap happened because the cylinder itself was heavily worn or faulty, replacing it at the same time makes practical sense. The cost of professional key extraction in South London typically ranges from £50 to £100, depending on the lock type and whether a replacement cylinder is also fitted.

Choosing the Right Replacement Lock

If your lock is more than ten years old, has been repeatedly problematic, or was a low-cost unit to begin with, replacement is usually better value than continued repairs. For your main entrance, look for a replacement that meets at least BS3621. Anti-snap cylinders are designed to break at a sacrificial point outside the door rather than allowing the core to be accessed — the current industry recommendation for UK front doors is a cylinder carrying the TS007 3-star kitemark.

Frequently Asked Questions

Can I fix a stiff lock myself?

Often, yes. If the stiffness is due to a dry cylinder, graphite lubricant applied to the keyhole will usually resolve it in seconds. If the problem is misalignment, adjusting the strike plate yourself is worth trying. If neither works after one or two careful attempts, a locksmith can diagnose and fix it in under 30 minutes.

My key turns but the door is completely stuck. Is the lock broken?

Not necessarily. On uPVC doors, the most common cause is a failed multi-point mechanism or a misaligned strike plate rather than a broken cylinder. Open the door from the inside if possible and watch whether the hooks and bolts engage when you operate the handle.

How much does it cost to get a broken key extracted?

In South London, professional key extraction typically costs £50 to £100. If the cylinder is undamaged you will only need a new key cut. If the cylinder needs replacing, expect to pay an additional £30 to £80 for a quality anti-snap unit.

Is it safe to use WD-40 on a stiff lock?

WD-40 is a water displacer, not a long-term lubricant. It will ease a stiff lock briefly but attracts dust and debris over time. Always use dry graphite lubricant or a dedicated lock lubricant spray instead — these do not leave an oily residue and are safe for all cylinder types.