A Roommate Moved Out. Which Locks Actually Need Changing?

The reason to change a lock is almost never suspicion of a specific person. It is arithmetic. Over three or four years a flat produces keys the way a drawer produces takeaway menus: one for a partner, one for a housemate's parent visiting, one cut for a dog walker, one that went into a bag and never came back.

Nobody set out to lose track. But when somebody moves out and you sit down to count, the honest answer is usually that you do not know how many exist or where they are. That is the moment worth acting on, and it is not personal.

Rekeying resets that count to the number of keys you are holding. The lock stays on the door and takes new pins, so every key cut before today stops working, including the ones you have forgotten about.

Your own flat door: yes, always. That is the lock that matters and it is the one you can order yourself. It is $28 to $46 per cylinder, and if your door carries two locks — a latch and a deadbolt, or a landlord's addition above the original — both can be brought onto one key in the same visit.

The street gate or lobby door: no, and you could not anyway. That lock is shared, so changing it needs the building rather than a resident. In practice it also matters less than people think: a gate key opens a gate, not your flat.

Any door of yours that is separate: a storage cage, a garage under the building if it is assigned to you, a bike room if it is yours alone. Those follow your flat door. Anything shared follows the building.

Changing hardware on a rented door needs your landlord's agreement, because the lock is part of the property. In most cases this is a short and uncontroversial conversation, especially when a tenancy has changed, and many landlords would rather it happened than not.

What tends to go wrong is doing it without asking and then discovering the lease requires the landlord to hold a key. Ask first, offer a copy, and the whole thing is routine. A written note of what was done, which the receipt provides, is usually enough for the file.

If you are locked out in the meantime, that is separate and needs nobody's permission: ID with the address, or ID plus a lease page or addressed mail, and you are back inside.

The $89 service call is counted once for the stop rather than once per lock, so several cylinders in one visit is much cheaper than the same locks on separate days. Second and third cylinders sit at the low end of the $28 to $46 range for exactly that reason.

It is a good moment to deal with anything else the door has been doing. A cylinder that has been stiff for two winters is going to fail whether or not anyone has moved out, and swapping it while the lock is already apart costs less than a separate visit later.

Ask for the old keys back rather than letting them be pocketed, and open every rekeyed door yourself before the work is written up. Both are small things and both are the difference between a job done and a job finished.