Master Key Systems Explained

A master key system is a lock configuration where one key (the master key) can open multiple locks, while each individual lock also has its own unique key that only opens that one lock. This is called a keyed-alike-but-controlled-access setup.

For homeowners, this is useful in properties with multiple entry points, granny flats, rental properties, or homes shared between family members with different access needs. Instead of carrying a large bunch of keys, the property owner holds a single master key that opens everything, while a tenant or family member has a key that only works on their door.

How the Cylinder Hierarchy Works

Most master key systems use a tiered structure:

• Grand Master Key: Opens all locks across an entire system (common in large commercial buildings or multi-property setups)
• Master Key: Opens a defined group of locks
• Change Key (or Sub Key): Opens only one specific lock

For a typical Australian home or small investment property, you'll be working with just master keys and change keys. The complexity increases as you add more locks or access zones.

Choosing the right system starts with understanding the main options available from Australian suppliers and locksmiths.

Access Hardware's 7000 Series barrel exchange system is a commonly used option in Australia, with individual barrels retailing around $7.40 (excl. GST) at trade pricing. The total cost climbs quickly once you factor in labour and the number of cylinders required.

For a standard single-family home, a master key system is not always necessary. But there are situations where the investment makes clear practical sense:

• You manage a granny flat or Airbnb on the same property and want different access levels
• Your home has a main entry, side gate, garage, and shed, and you want one key for everything
• You have elderly family members or carers who need controlled access
• You own a small strata or duplex property

The long-term benefit is convenience and control. A patent-protected system also means keys cannot be copied at a hardware store, reducing the risk from lost or stolen keys.

The Hidden Costs to Watch For

One area that catches homeowners off guard is lock compatibility. If your existing deadbolts or knobsets use incompatible barrel formats, the locksmith may need to replace entire lock bodies rather than just rekey existing ones. This can push total costs well above initial quotes. Always ask your locksmith to inspect your current hardware before accepting a quote.

A professional locksmith follows a structured process to design and install a master key system. Here is what that typically looks like for a residential job:

1. Site assessment: The locksmith inspects all entry points, notes existing lock brands and cylinder types, and identifies any incompatibilities.
2. System design: Based on your access requirements, the locksmith maps out which keys open which locks. This is sometimes done using a master key matrix or key schedule.
3. Hardware selection: The locksmith specifies cylinders that can be masterkeyed together. All cylinders must be from the same system or family.
4. Pinning the cylinders: Each cylinder is individually pinned in the locksmith's workshop or on-site to match the master key configuration. This is skilled work requiring precision.
5. Installation and testing: Cylinders are fitted to the locks, and every key is tested across every lock to confirm the hierarchy works correctly.
6. Key registration (for patent systems): Your details are registered with the manufacturer or distributor, meaning additional keys can only be cut with your authorisation.

Most residential jobs take between two and four hours. At $80–$150 per hour for labour, plus hardware, a straightforward three-lock master key system typically comes to $350–$700 all up.

Master key systems are not a DIY job. You need a licensed locksmith with experience in keyed-entry systems and master key design. In Australia, locksmith licensing is managed at the state level, so confirm your locksmith holds a valid licence in your state or territory before proceeding.

There are currently over 700 locksmith businesses operating across Australia, with strong representation in major cities. Melbourne has 216 listings, Sydney 179, Brisbane 90, Perth 72, Adelaide 56, and the Gold Coast 44. The average rating across reviewed businesses sits at 4.7 out of 5 stars, which reflects a generally high standard of trade work.

Some highly rated businesses worth knowing about include Terry's Locksmiths (4.9 stars, 3,017 reviews), Tas Mobile Locksmith (5.0 stars, 1,591 reviews), Express Locksmith Gold Coast and Tweed (5.0 stars, 1,375 reviews), Wynns Locksmiths Preston (4.8 stars, 1,390 reviews), and Sheehan Locksmiths (4.9 stars, 934 reviews).

Questions to Ask Before You Hire

• Are you licensed in this state?
• Do you work with patent-protected master key systems?
• Will the cylinders you install be compatible with my existing locks?
• Can you provide a written key schedule?
• What is included in the quote, labour and hardware?