My ex-partner kept the key to the apartment - is it worth changing the lock?

The client's name and specific details of the situation have been changed to maintain confidentiality. The story is based on typical situations with which apartment owners turn to door specialists.

Let's call the client Anna. After several years of marriage, Anna broke up with her partner. He moved out of the apartment, took his personal belongings and returned the key.

At first glance, the issue was closed. But a few days later Anna began to think: he had indeed returned the key, but she could not know whether an additional copy had ever been made.

There were no direct threats. The ex-partner did not try to get into the apartment, and there was no reason to expect a conflict either. Nevertheless, an unpleasant feeling remained:

“I live here alone and I don’t know for sure if anyone else has a key to my door.”

It was the lack of control over existing copies of keys that caused the appeal.

Is it possible to find out if a copy of the key was made?

For most conventional mechanical keys, this is impossible to determine. If a person has ever had a key in their possession, it is technically impossible to guarantee that a copy has not been made.

The return of the original key only confirms that the specific copy is again in the possession of the owner. It does not confirm the absence of other keys.

Is it necessary to change the entire lock in such a situation?

Not necessarily. In many doors, access control is determined by a cylinder. If the lock body, door hardware and other components are in good condition, sometimes it is enough to replace just the cylinder and get a completely new set of keys.

The old keys then stop opening the door. In other types of locks, a different solution may be required - for example, recoding or replacing the mechanism itself.

Therefore, it is first wise to determine which lock is installed on the door.

When does replacement make sense?

The main question here is not whether you trust a particular person. The question is much simpler: can you say exactly who currently has access to the apartment? Replacing a cylinder or lock makes sense if:

• it is unknown how many copies of the key existed;
• the key was with another person for a long time;
• relationships with a person have changed;
• the apartment owner simply wants to regain full access control.

Sometimes the latter is a sufficient reason.

What can be done?

Take a photo:

• door from the inside;
• lock;
• cylinder;
• end part of the door;
• existing key.

From a photograph, a technician can often understand which mechanism is installed and whether it is possible to replace only part of it.