Commercial & property management

Master key systems explained for building owners and managers

A master key system lets one key open every door while each tenant or employee’s key opens only their own. Simple to describe, and very easy to get wrong if nobody draws it on paper first.

By Timmy Creighton, founder and licensed locksmith · Major Key Locksmith · October 2026

The levels

Change key. Opens one lock, or one group of locks: a unit, an office, a closet. This is what most people carry.
Master key. Opens every lock in a group. The cleaning crew’s key for one floor, or the super’s key for one building.
Grand master key. Opens every lock in the system. Very few people should hold one.

Larger properties add more levels. Most small buildings need fewer than they think.

How it works inside the lock

A master-keyed cylinder is pinned so that more than one key cut will turn it: the change key and the master key both line the pins up. That is what makes the system work, and it is also the trade-off: every extra level adds ways a cylinder can be opened. A good design uses only the levels the building really needs.

Design comes first

The part that decides whether a system works for years is the keying schedule: a written plan of every opening, which key runs it, and who holds what. Without one, the next locksmith guesses, and within a few years the system has keys that open doors nobody intended.

We sell that step as a fixed product. A design visit is $600: we walk every opening, record the existing hardware, design the hierarchy with you, and hand you a written keying schedule and a costed quote. Cylinders, hardware and keys are quoted per opening after the survey. Rekeying existing cylinders into the new system is $55 each, on top of the mobile service charge for that visit.

Protect the system

A master key cut on a standard keyway can be copied at a hardware counter, and then the whole design is compromised. For buildings with turnover, use a restricted keyway, keep a key register, and never let the grand master leave the people it was issued to.

Questions people ask

Can you add to an existing master key system?

Usually, if the original keying schedule exists. Without it, the system has to be decoded before anything can be added safely, and sometimes it is better to start fresh.

Who keeps the keying schedule?

You keep it, and we retain a copy. It belongs to the building, not the locksmith.

Is master keying less secure than separate keys?

Slightly, because each cylinder accepts more than one key. A well-designed system with a restricted keyway and only the levels you need keeps that trade-off small.

Want a straight answer about your building?

Tell us what you are dealing with. We will say what it needs, what it costs, and whether it is a job for us at all.

Master key systems Call 973-922-3597

Keep reading

Master keys or access control? An honest comparison When keys are the right answer, when fobs earn their cost, and why most buildings use both.Read → Do Not Duplicate keys: what the stamp really does, and what works The stamp is a request, not a lock. What actually stops copies.Read → A locksmith’s unit turnover checklist for property managers Every unit lock, the mailbox, codes and fobs, and the key log that makes the next one faster.Read → Access control basics: strikes, maglocks, readers and fail-safe Strikes vs maglocks, fail-safe vs fail-secure, and why the door matters more than the reader.Read →

Any price mentioned here is the one published on our pricing page as of October 2026. The final price is always confirmed with you before any work begins. More answers from the blog →