Can I replace a door lock myself?

A euro cylinder usually comes out in a few minutes. With the door open, undo the long fixing screw in the edge of the door, level with the keyhole, then put the key in and turn it slightly until the cam lines up and the cylinder slides out. The new cylinder goes in the same way. Test it several times with the door open before you close it.

Size is the usual catch. Euro cylinders are sold in many lengths, measured from the fixing screw hole to each end, and the two sides are often different. West Yorkshire Police advise that a cylinder should not be left sticking out from the door or handle. A cylinder that protrudes tends to be easier to grip and snap, so measure both sides before you buy.

Choose the standard as well as the size. West Yorkshire Police name two national standards for cylinders, TS007 and Sold Secure Diamond (SS312), and recommend 3 stars as the minimum when upgrading: a 3 star cylinder, or a 1 star cylinder with a 2 star handle. A cheaper cylinder without either mark saves money but tends to offer less protection against snapping. Check your insurer's requirements too.

Mortice locks on wooden doors are harder. Swapping like for like into the same pocket can be manageable, but a different size usually means cutting the door, and a poor fit can weaken it. The Master Locksmiths Association says to look for BS3621 stamped on the faceplate, and that some insurers insist on it. A failed multipoint mechanism or gearbox is a repair job, not a lock change.

If you rent, check your tenancy agreement and speak to your landlord first. If you would rather not do it yourself, our lock change is £85 between 8am and 6pm on weekdays, plus £25 for a standard euro cylinder or £60 for a TS007 3 star anti snap one, with travel and up to one hour on site included and the price fixed before we set off.

Related questions

• Is it cheaper to rekey a lock or replace it?
• How much should it cost to change a lock?
• How do I know if I have anti snap locks?