Changing locks can feel like the first practical step when keys are lost, staff move on, tenants change, or a property layout needs better security. But if you are considering a master key system, the key plan should come before the hardware change.
A well-made key plan sets out who can open which doors, which keys sit above others in the hierarchy, and which locks need to be re-cored or replaced. Without that planning, a property can end up with new locks that work today but become awkward, expensive, or limiting when access needs change.
For Melbourne homes, offices, clinics, retail sites, warehouses, and mixed-use buildings, a master key system can make access simpler and more controlled. The best results come when the system is designed around the property before any cylinders are ordered, keyed, or installed.
This guide explains how to plan a master key system before changing locks and avoid common security mistakes.
Start With The Reason You Are Changing Locks
Before you decide how many keys you need, be clear about why the locks are being changed in the first place. Different reasons call for different levels of planning.
You may be changing locks because a key has gone missing, a tenant has vacated, an employee has left, or a business has taken over a new premises. You may also be upgrading old hardware, separating staff-only areas from public areas, or simplifying a property where too many keys are already in circulation.
That reason matters because it affects the urgency, the scope, and the access rules. A lost master key may require a more serious response than replacing worn cylinders on a single doorway. A new commercial fit-out gives you time to design a clean hierarchy from the start. A change of tenancy may need a practical short-term rekey first, followed by a larger planned system.
For business premises, we usually recommend treating the lock change as part of a wider security review. Our commercial locksmiths can assess existing hardware, door use, staff access, and future requirements before recommending a system structure.
For homes, the same logic applies on a smaller scale. A large home with a studio, side gate, office, rear entry, and separate storage area still needs a clear access plan if different people need different keys.
Map Every Door Before You Think About Keys
The most common planning mistake is starting with the keyholders instead of the doors. A master key system should begin with a door-by-door map of the property.
Walk through the site and list every lock that may form part of the system. Include front entries, rear exits, internal offices, storerooms, plant rooms, shared facilities, gates, staff-only rooms, bathrooms, cleaner access points, and any separate tenancies or private areas.
For each door, write down:
- What the door protects or separates
- Who currently uses it
- Who should continue using it
- Who should not have access
- Whether access is needed during business hours, after hours, or both
- Whether the existing lock works properly
- Whether the door is likely to change use later
This gives your locksmith a practical access map rather than a vague request for “one key for everything”. It also helps identify doors that should not sit under the same key level.
For example, a clinic might have a reception entry, consultation rooms, a staff room, a records room, and a storage room. Those doors should not all be treated the same. A property manager, practice manager, clinician, cleaner, and receptionist may each need a different level of access.
Planning at door level helps avoid over-permissioning, where too many people receive access to areas they do not need.
Decide Your Access Levels
Once you have mapped the doors, the next step is deciding the access levels. This is where the master key system becomes a structured hierarchy rather than a collection of unrelated locks.
At its simplest, a master key system has two levels:
- A master key that opens all locks in the system
- Change keys that open only assigned locks
More complex properties may need additional tiers. A sub-master key can open a group of doors within one area, while the top master key opens the whole system. A larger building may have separate sub-master groups for management, cleaning, administration, tenancy areas, and maintenance access.
The aim is not to create the most complicated system possible. The aim is to create the simplest system that reflects how the property is actually used.
A good planning question is: if this person lost their key, what parts of the property would be exposed? That question quickly reveals whether a key level is too broad.
For example, a cleaner may need after-hours access to common areas, bathrooms, and service corridors, but not private offices or stock rooms. A store manager may need access to the shopfront, office, and back-of-house areas, but casual staff may only need the main staff entry and shared work areas.
When the hierarchy is clear, the key system allows each person to carry fewer keys while still limiting access to what they genuinely need.
Understand The Difference Between Master, Sub-Master And Change Keys
The language around master key systems can be confusing if you only deal with it occasionally. Before changing locks, it helps to understand the key types your locksmith may discuss.
A master key opens every lock assigned to that master key level. In a small system, this may mean one owner or manager key that opens all relevant doors on the property.
A sub-master key opens a defined group of locks, but not the entire system. This is useful where one person needs broad access within a section, but not full access everywhere. A floor manager, building supervisor, senior clinician, facilities worker, or department head may hold a sub-master key.
A change key opens one lock or one limited group of locks. This is the key type most users hold. It gives access only to the areas that person needs.
In larger systems, a grand master key may sit above multiple master groups. That level should be planned carefully and issued sparingly, because it carries the widest access.
Put simply, the key plan sets out which keys open which locks according to an agreed access hierarchy. The value comes from deciding that hierarchy before the locksmith begins re-coring cylinders or replacing hardware.
Review Existing Locks Before Replacing Everything
Planning a master key system does not automatically mean every lock must be replaced. Some existing locks may be suitable for re-coring or rekeying, while others may need replacement because they are worn, incompatible, damaged, low quality, or not appropriate for the access level you need.
A licensed locksmith will assess the hardware on site and explain what can be retained. This can include checking lock cylinders, door condition, keyway compatibility, latch function, and strike alignment.
There are three common outcomes:
- Some locks can be re-cored into the new system
- Some locks can stay in place but need servicing or adjustment
- Some locks should be replaced to support the new access design
This matters because a master key system is only as reliable as the locks it depends on. Poorly functioning doors, loose hardware, or mismatched cylinders can undermine a well-designed hierarchy.
For residential properties, our residential locksmiths can advise whether a smaller system is practical, or whether standard rekeying is the better fit. For commercial sites, the assessment usually includes a broader discussion about staff access, shared areas, and future expansion.
Plan Key Control Before Keys Are Cut
A master key system should not stop at the lock cylinders. Key control is just as important as the physical installation.
Before keys are cut, decide who is authorised to request additional keys, how approvals will be recorded, and what happens when a key is lost or a keyholder leaves. If nobody owns that process, key control tends to weaken over time.
For workplaces, assign responsibility to a specific role rather than leaving it informal. That may be the business owner, operations manager, facilities manager, building manager, or another senior person. For residential rental or shared properties, the responsible person may be the owner, agent, or property manager.
You should also keep a current key register. At minimum, it should record:
- The keyholder’s name or role
- The key level issued
- The date issued
- The number of copies issued
- The person who authorised the issue
- The date the key was returned or cancelled from use
Restricted key systems can strengthen this process because keys cannot be copied casually. Additional keys must be ordered through an authorised pathway, giving you better control over duplication.
This is especially useful for businesses, shared buildings, managed residential properties, and any site where many people hold keys over time.
Think About Future Changes, Not Just Today’s Layout
A master key system should work for the property now, but it should also allow for reasonable change. Before you approve the final key plan, think about how the site may evolve.
Will your business add staff? Could one office become a consulting room? Will a storage area become a staff-only zone? Could a tenant move out? Are you planning to add another entry point, gate, or internal separation later?
Your locksmith does not need to predict every future change, but they do need to know if expansion is likely. A system can often be designed with room for future doors or additional sub-master groups. If that is not considered upfront, later changes may require more rekeying than expected.
This is particularly important for:
- Growing small businesses
- Multi-tenant commercial properties
- Medical, dental, and allied health practices
- Warehouses with office and storage areas
- Retail sites with changing staff structures
- Large homes with separate work or guest areas
Good planning keeps the system practical. Overbuilding the hierarchy can make everyday use confusing. Under-planning can force avoidable changes later.
Avoid These Planning Mistakes
Most problems with master key systems come from rushed decisions before installation. The locks may be fitted correctly, but the plan behind them may not suit the property.
Avoid giving too many people high-level keys. A master key should be held only by people who genuinely need broad access. If many people need the same high-level key, the access structure may need to be redesigned.
Avoid grouping doors only by convenience. Two doors may sit near each other but need different access rules. A staff room and a private office may be side by side, but they should not necessarily sit under the same change key.
Avoid designing around one current employee or tenant. Key systems should follow roles and zones, not individual personalities. People move on, but the access logic should remain useful.
Avoid ignoring after-hours access. A person may need access during the day when other staff are present, but not outside normal operating conditions. Your key plan should reflect real access requirements, not assumptions.
Avoid waiting until installation day to raise concerns. Once cylinders are keyed, late changes can create extra work and cost. The planning stage is the time to ask questions and adjust the structure.
If you need help reviewing a site quickly, our mobile locksmith team can attend properties across Melbourne and assess what needs to be rekeyed, re-cored, or replaced.
What To Prepare Before Calling A Locksmith
You do not need a technical drawing before speaking with a locksmith, but preparation makes the consultation more productive.
Before calling, gather:
- A rough list of doors and locks
- Photos of existing locks, if available
- A list of current keyholders
- Any known lost or unreturned keys
- The access levels you think you need
- Whether the property is residential, commercial, or mixed-use
- Any upcoming changes to layout, tenancy, or staffing
- Whether you want restricted key control
This helps the locksmith give clear advice instead of making assumptions. It also separates urgent work from planned work.
For example, if a former staff member has not returned a key, you may need immediate rekeying for exposed areas. But if you are also planning a master key system, it may be more cost-effective to design the long-term system at the same time rather than paying for two separate lock changes.
Nonstop Locksmiths provides mobile locksmith support and master key system planning across Melbourne. We are licensed and insured, available 24 hours a day, 7 days a week, and able to advise on both immediate lock changes and planned access upgrades.
Speak With A Melbourne Locksmith Before Changing Locks
If you are about to change locks and want the option of a master key system, speak with a locksmith before the work begins. A short planning conversation can prevent unnecessary rework and help you choose the right structure from the start.
Our licensed and insured locksmiths can assess your property, explain your options, and design a practical key plan for your home, business, or managed building. We provide rapid response across Melbourne and are available 24/7 for urgent lock changes as well as planned master key system work.
Call 0418 444 166 to speak with Nonstop Locksmiths, or contact us to discuss your property and access requirements.
