Master Key Systems Explained

Walk into the maintenance office of almost any apartment building, school or plant and you'll find the problem a master key system solves: a board of keys, a ring the size of a fist, and nobody quite sure which key opens the boiler room. A well-planned master key system replaces that with a simple rule. Everyone carries one key, and that key opens exactly the doors they need, no more and no fewer.

How a master key system works

Lock maker Allegion describes master keying as a method of controlling access through a building: each lock has its own key, but all the locks in the system can also be operated by one master key. That's possible because the cylinder is built to accept more than one key. Inside a master keyed cylinder, extra pins create a second point where the lock will turn, so both the individual key and the master line up correctly.

The levels of a system

Systems are described by levels, from the narrowest key at the bottom to the widest at the top.

• Change key. The bottom level. A change key opens one lock, or one small group of locks keyed alike, such as a single suite. A tenant, an employee or a student usually carries a change key.
• Master key. Opens every lock in one group. A floor manager might carry a master for their floor, or a department head for their department.
• Grand master key. Opens every lock in every group. As Allegion puts it, each group is independent of the others, and the grand master works with all locks in all groups. The owner, property manager or head of maintenance usually holds it.
• Great grand master. Large campuses and multi-building sites sometimes add a level above that, so each building has its own grand master and one key opens the whole site.

Many buildings are well served by two or three levels. Every level you add increases the number of keys that can operate each lock, so more levels aren't automatically better.

An example: a three-storey office building

Picture a building with four suites on each floor. Each tenant's change key opens only their own suite. The floor's master key, held by the cleaning contractor for that floor, opens all four suites on it. The building manager's grand master key opens every suite on every floor, plus the electrical, mechanical and janitor's rooms. The front entrance can be set so every key in the system opens it. If a tenant loses a key, only that suite needs rekeying. If the cleaner leaves, only that floor's master is affected.

Keyed alike, keyed different and master keyed

These terms come up whenever locks are ordered, and they mean different things:

• Keyed different. Allegion defines it simply: each lock can only be opened by its own individual key.
• Keyed alike. A group of locks all work with the same key. Useful for the front and back door of a house, or a set of padlocks on a site.
• Master keyed. Each lock, or each keyed-alike group, has its own change key, and a master opens them all.

Padlocks, camlocks and mailbox locks can be part of the picture too. Padlocks can be keyed alike, keyed different or keyed to an existing home or business key.

Key control: the half people forget

A master key system is only as secure as its keys. With a standard key blank, anyone holding a master can walk into a hardware store and have it copied, and then nobody knows how many masters exist. That's why serious systems use a restricted or patented keyway: key blanks that are not sold to the public and can only be cut through an authorized dealer.

Mul-T-Lock is one example. For its MTL600 platform, it describes enhanced key copy control: the platform comes with a unique magnetic card that should be presented to an authorized Mul-T-Lock locksmith, and MTL600-based master key systems are offered for organizations. Cote Lock is a Mul-T-Lock Super Center, and keys for Mul-T-Lock systems are cut under our own Mul-T-Lock account, so only an authorized dealer can duplicate them.

Key control also means keeping records. A key schedule lists every lock and every key in the system, and who holds each one. Keep it current, collect keys when people leave, and you'll know exactly what to rekey when something goes missing.

When a building needs a master key system

• Rental buildings with several units, where tenants need their own keys and staff need access to all of them.
• Offices and plants with separate areas such as offices, shipping, tool cribs and electrical rooms.
• Institutions like schools, clinics and churches, where staff need different levels of access.
• Any building with turnover, where it's cheaper to rekey one suite or one group than every lock in the building.
• New construction and renovations, where keying is planned before the hardware goes in.

Planning one well

1. List every door and what it protects, including closets, mechanical rooms and gates that are easy to forget.
2. Group the doors by who needs them, and decide which keys open which groups.
3. Leave room to grow. A system designed with spare capacity can add floors or tenants later without starting over.
4. Choose the keyway based on how much key control you need; a restricted keyway for masters, at least.
5. Decide where keys can't solve it. Doors with constant turnover often suit access control with fobs or cards, while interior doors stay on keys.
6. Keep the key schedule and review it whenever someone leaves.

What a system costs

It depends on the size of the building and the hardware chosen. Green Building Canada says the cost of a master key system depends on the complexity of the building. Experts.ca lists commercial high-security lock installs at $250 to $600 or more per lock, plus master key and access systems. Many existing locks can be rekeyed into a system rather than replaced, which keeps the cost down. Our locksmith cost guide has more published figures.

How Cote Lock can help

Master key systems and high-security systems are one of our specialities, alongside commercial door hardware. We design and install systems for property managers, commercial and industrial buildings and institutions, and rekey them as people come and go. Steve D., who uses us for new construction and renovation keying, put it this way:

We use Cote Lock extensively for both new construction and renovation keying work. They provide efficient, friendly service consistently and support our business well. I can enthusiastically recommend them! (Steve D.)

Read more on our master key systems and high-security locks pages, call 519-894-7055, or request a quote.