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Master key systems

A master key system lets one key open several doors while each user's own key opens only theirs. Fitting is charged as labour, £65 to £85 an hour in daytime across the Master Locksmiths Association's 2026 list, Checkatrade and Bark, with the cylinders made to order and priced to the plan. Offices, blocks of flats, schools and landlords use them.

Illustration: three keys on a ring

What this covers

Typical price. Fitting is usually charged as labour, at £65 to £85 an hour in daytime across the MLA's 2026 list, Checkatrade and Bark, with the cylinders priced to the key plan.

What the job covers

  • Surveying the doors of a building and drawing up a key plan
  • Ordering and fitting master keyed cylinders made to that plan
  • Keying the front and back doors of a house alike
  • Adding new doors to an existing master key system
  • Replacing cylinders when a master key is lost

What is involved

A master key system is a set of locks built to a plan, so that different keys open different groups of doors. At the bottom are the individual keys, each opening one door or one flat. Above them, a master key opens a group, such as one floor or one department, and a grand master opens everything. A building can have several levels, and a key can be made to open any chosen set of doors.

Keyed alike is the simpler relative: several locks that all take the same key, such as the front and back doors of a house. It is often what a homeowner or small landlord actually needs.

The work starts with a survey. A locksmith lists every door, who needs to get through it, and how that is likely to change. From that comes a key plan, a chart of which key opens which lock, and the cylinders are made to it by a cylinder maker or supplier. The locksmith then fits them and hands over the keys with a register of who holds what.

Most systems use a restricted key profile, protected by patent or registration, so that copies can only be ordered from the supplier against the building owner's authorisation. Without that, a master key copied once can open every door it covers.

There are trade-offs. Every extra level of master keying adds to the work and cost of the cylinders, and a lost master key affects every door it opens, so the plan should say how cylinders will be replaced if that happens. A good plan also leaves room for doors that do not exist yet.

Choosing someone for the job

Ask for the total before work starts: the cylinders, keys, fitting and VAT, and how cylinders and keys will be priced if you add doors later. Ask who makes the cylinders, whether the key profile is restricted, and who is allowed to order copies. Ask for the key plan and a key register in writing, and how they are kept. Ask what happens if a master key is lost: which cylinders would change and roughly what that would involve. If the building has fire exits, check the new locks still let them open from inside without a key.

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Common questions

What is a master key system?

A set of locks made to a plan, so that one key opens several doors while each person's own key opens only theirs. A grand master key opens everything, master keys open groups of doors, and individual keys open one. Offices, flats, schools and landlords use them.

What is the difference between master keyed and keyed alike?

Keyed alike means several locks all take the same key, such as a house's front and back doors. Master keyed means each lock has its own key, and a separate master key opens all or some of them. Keyed alike is simpler and suits most homes.

What happens if a master key is lost?

Every lock it opens is affected, so the cylinders it fits may need changing or reworking. That is why the key plan should say what happens if a master key goes missing, and why master keys should go to as few people as possible and logged in a key register.

Can master keys be copied?

Not if the system uses a restricted key profile. Copies can then only be ordered from the cylinder supplier against the building owner's authorisation. Without a restricted profile, a master key can be copied like any other, which defeats the system.

Can a master key system be added to later?

Usually, if the original plan left room for it. New doors get cylinders made to the existing plan by the same supplier. Ask for this when the system is first designed, and keep the key plan and supplier details somewhere safe.

Does a master key system make each lock less secure?

Each extra level of master keying adds combinations a cylinder will accept, so a heavily master keyed cylinder can be less resistant than a standalone one. A locksmith designing the plan should keep levels to what the building needs and fit cylinders to a recognised standard.

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