Door won't lock: diagnosis and solutions

The door shuts, but the key refuses to make its full turn. Or you have to pull the door towards you, lift it, give it a shoulder before the bolt will agree to engage. Plenty of people live for months with this ritual — until the evening it won't go at all, or worse, until the burglary when the insurer notes that the door wasn't properly locked. This guide explains why a door stops locking and what can be fixed easily.

The two-minute diagnosis

The test is the same as for a stiff lock: lock the door open.

• Door open, everything works — bolts that throw cleanly, a smooth key: your lock is in good health. The problem is the alignment between the door and its frame: the bolts no longer land opposite the strike plates. This is the case in the vast majority of situations.
• Door open, the mechanism already jams — the lock itself is at fault: a worn mechanism, a multipoint linkage out of adjustment, or a tired cylinder.

A second useful clue: if lifting the door by the handle while you lock makes things easier, the door has dropped on its hinges. If the problem appeared with the rain or the damp, the wood has swollen.

The causes on the door-and-frame side

The door has dropped

A front door is heavy — often more than 40 kg for an old Brussels door. Year after year, the hinges wear or develop play, and the door drops by one to three millimetres. That's all it takes for the main bolt to scrape against the edge of the strike plate instead of going into it. Adjusting or replacing the hinges fixes the problem for good.

The wood has swollen

The great Belgian autumn classic: a wooden door can gain several millimetres in width with the damp. Locking gets stiff in November and goes back to normal in April. As long as it's seasonal, adjusting the strike plate is often enough; planing is the last resort, and best done properly so you don't end up with a draught in winter.

The strike plate has shifted

The screws of a strike plate work loose every time the door slams. A strike plate that's moved by two millimetres is enough to block a bolt. It's the simplest repair — provided the strike plate is moved to the right spot, rather than the hole being enlarged with a file as you see all too often, which ruins the precision of the locking.

The causes on the lock side

The multipoint lock out of adjustment

A multipoint lock locks at three, five or seven points linked by a linkage. If a single point catches, the whole operation stiffens. Multipoint locks need fine adjustment: each point has to land exactly opposite its strike plate. It's a locksmith's job, but a quick one when it's done with the right tools.

The mechanism is worn

Tired springs, a bolt that no longer throws fully, a handle that won't spring back: a worn lock case gets replaced. If the lock is more than fifteen years old, it's a good moment to take stock of the overall security level — our guide on choosing a security lock gives you the bearings, and our lock replacement service handles the rest.

Why you shouldn't wait

A door that locks badly always ends up not locking at all — and statistically, on an evening when you're in a hurry. But the real risk lies elsewhere: a door that isn't locked with the key can compromise your insurance cover in the event of a burglary. Many Belgian policies require effective locking for full theft cover; our guide on insurance, burglary and locks sets out this point. A door you no longer lock "because it's become too stiff" is exactly the scenario that causes trouble.

Adjusting a door that shuts badly is a short job, easy to plan, no emergency about it — far better to do it before it becomes a blocked door on a Sunday evening. And if you're already at that point, we're out around the clock.