Master Key Systems Explained


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  1. What is Master Keying?
  2. What are the benefits of Master Key Systems?
  3. Access Levels to a Master Key System
  4. Master Key Vs. Grandmaster Key
  5. What type of Master Key System should I use?

What is Master Keying?

Master keying refers to a mechanical locking system used throughout a building whereby one key can access multiple locks. This system, also known as a master key system (in reference to the master key which accesses all locks), is used to provide or limit access to different locked areas within a building or complex.

Master key systems use cylinder locks which can be accessed as normal by an individual key designed for the lock. However, master keyed locks also feature additional pins – referred to as a wafer pin or master shim – which allows it to not only be accessed by an individual key, but a master key(s) also.

The master shim is inserted between the top and bottom pins within a cylinder lock, so that there are two different shear lines, meaning the master keyed lock can be accessed by at least two different keys.

Alongside the master key, there may also be multiple sub-master keys. A master key system works on a key distribution hierarchy; this means sub-master keys will have more access than a key used for a singular lock (a differ key) but will not have access to the same number of locks as a grand master key.

Due to the complex nature of this type of hierarchical system, careful planning is needed whilst designing bespoke key management systems to ensure a safe and secure locking system.

What are the benefits of Master Key Systems?

There are numerous benefits to using a master key system, including increased convenience, security, peace of mind and control.

Convenience & peace of mind

A master key system with high security locks ensures total peace of mind for both residents of a building and its management team. Master keying makes certain restricted areas remain secure, whilst also granting access to specific people in case of emergencies or protocol.

The convenience of managing a reduced number of keys can also bring peace of mind in emergencies such as fires, as well as saving critical time ensuring exit routes are open and all residents have been evacuated safely.

A reduced number of keys can also save costs when making and replacing keys.

Increased security

The calculated key management plans within a master key system ensure all access is predetermined – meaning, specific keys grant specific access.

This increases security for all those involved, including both residents and management teams, and any goods which need to be safely stored away.

The reduced number of keys involved in a master key system, since one key is needed per person rather than multiple, ensures there are fewer keys that go missing or become stolen, which further increases the security of a building or complex.

Higher level of control

Master keys also increase the level of control a person has over a property. Not only is access controlled at all levels, but restricted master key system keys cannot be duplicated at local key bars, they are only available to order by the master key registered owner directly from the master key system manufacturer.

This means keys cannot be copy cut by unauthorised key holders, such as HMO tenants, maintaining the security of the master key suite.

And, because it’s much easier to track the levels of access people have, it can be easier to detect the cause of break-ins and thefts.

Where you might find a master key system in use

Master key systems are typically used within high security multi-occupation buildings and complexes such as apartment complexes, schools, office spaces, and care homes. Correct key management is a way of increasing commercial security within environments.

Landlords and multi-occupational houses

In houses with multiple occupants (HMO), managed by a landlord, and large complex blocks, it can be advantageous to use a master key system.

This ensures that the landlord and other employees can still access all rooms for necessary maintenance, checks, or emergency work, whilst still making certain residents feel safe and secure in their rooms.

HMO Properties
Eductational Sector - UOB - University of Birmingham

Education Sector

A master key system is essential within schools and higher education buildings. Whether protecting young children from accessing potentially dangerous or hazardous environments or making certain expensive equipment and sensitive information be stored safely away.

A master key system can offer many benefits within educational environments.

Businesses with internal or multiple offices

Master keys ensure CEOs and other managerial employees in possession of master or sub-master keys can access offices, documents and equipment they need.

Whenever they need to, without other employees needing to be present.

Businesses with multiple offices
seurity guards with door access

Security guards

Key management is a great approach for those working in security positions.

It enables security guards to patrol areas with limited access, as well as making it easier to find the correct keys for each area – perfect for night patrols with limited visibility.

Care Homes

Care homes can benefit from limiting access to mentally or physically vulnerable residents, whilst still allowing staff to move through rooms freely.

It moreover gives peace of mind to family members knowing when the residents are in their rooms, they are safe and have some level of privacy.

Care homes Corridor
Cleaning Services

Cleaning Services

With a singular key providing access throughout a building or number of buildings, cleaning services often find it more convenient to use one key rather than search for multiple – especially independent services in charge of cleaning multiple premises such as HMOs, schools or offices.

Whilst allowing access to areas where needed but also have the flexibility to prevent access to other areas if required.

Find out how a Master Key System could be suited for your environment

MKS are the UK's leading door cylinder specialist for over 25 Years

master key system

Access Levels for a Master Key System

The master key system works on a tiered keying system basis. By increasing the number of tiers within the system, access becomes further compartmentalised with suited keys. For instance, the great grand master key sits on the top tier, with access to all lock systems below it. As you go down the tiers, access becomes more limited, ending with a differ key which can access an individual lock(s). Access levels start at the great grandmaster key, and move down to the grandmaster key, followed by a master key, sub-master key and finally ends with differ keys.

Great Grandmaster Key

The highest level of access, opening all grand master, master, and sub-key systems.

Grandmaster Key

Also known as GMK, with the second highest level of access, opening locks under master and sub master systems.

Master Key

The simplest key management, one sub-key can open any specified group of locks

Sub Master Key

This is the most basic set-up, with access to cylinders under sub keys; open multiple locks with one master key.

Differ Key

the very last tier of the key management, the differ can open any specified lock.

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Example Scenario - University Setting

In a university setting, Lecturers would have access to a sub key, which enables them access to a specific area.

The students would hold a differ key which would open their individual room accommodation.

Certain staff members, such as cleaners, may hold a master key – allowing access to the individual classrooms as well as cleaning cupboards and kitchens.

Those in higher, managerial positions may be given a grand master key, with access to every room within the campus block. Finally, a great grand master key will be given to a select few, with access to all areas within a university campus.

Master Key Vs. Grandmaster Key

Locks with master key access are the most basic master key system set up.

A grandmaster lock with master keys additionally used grants the same access as a master key, with another tier for greater compartmentalisation and access restriction.

So, for those looking for a more complex system with extra levels of access, grandmaster key or even a great grand master key system may be more suitable.

The UK’s Leading Door Cylinder Specialist for over 25 years

A British, family owned business with over 25 years designing and manufacturing high-quality door cylinder locking systems for commercial, industrial, healthcare and educational applications throughout sectors such as care homes, small HMO’s to schools and large complex academies.

By choosing Master key you are guaranteed both a premium solution coupled with customer satisfaction and support.

HMO / Multi Occupancy Locking Systems

Our website shows in graphic form how this works. There can be many levels to a cylinder master key system. A basic system is where all cylinder locks are opened by a single Master Key but each of the door cylinders are opened by their own key often referred to as the slave or differ key.

This system is typical for a HMO or Landlord whereby the Landlord wants his own single master key to open all the locks, but to ensure that the tenant has a differ key that is unique to their own door.

Very often, the Landlord will also have a Cylinder Lock fitted to the main door. This door cylinder can be opened by the Master Key and each of the tenant's keys and this is referred to as a common entrance. Whilst this is not recommended, it is by far the most convenient Master Key System for HMO’s and landlords.


Euro Cylinder Locks

Euro Cylinder lock Master Key Systems are in most circumstances, commissioned for convenient access whilst being able to work with a more complex Master Key System and limit access to individual key holders. All of this is possible because of the unique design of door cylinder locks that have been developed over many decades and re-engineered in recent years to tolerances that allow them to be Master Keyed.

Before designing or commissioning a Euro Cylinder lock Master Key System, a degree of careful thought should be given to what is required of the system by the principal (Master Key Holder) and the other users whilst allowing for expansion (as more users may need to use the system in the future). The starting point for this process is to determine how many doors there are that will require cylinder locks and how many extras may be required over the forecast life of the Master Key Suite.

A basic Master Key System Planner is available on our website. If something more complex is required, then MKS have a range of Excel charts to suit all types of Master Key Systems however complex. Having decided on the elements of doors, cylinders and users plus allowing for future expansion, the next level is deciding the levels of access, for example, you may require some doors to be opened by more than 1 user but exclude others from individual key holders or Sub Master Keyholders.

What Type of Master Key System should I use? 

Traditionally Cylinder Locks were measured excluding the operating cam, for example, a 60mm euro-cylinder would be specified as a 25/10/25 the 10 being the dimension of the cam.

Today this is not so common. With the advent of PVCu doors and large security doors, it has brought about the need for offset cylinder door locks. As an example, a 100mm cylinder could be split 40/60, i.e. from one end of the cylinder to the centre of the cam it measures 40mm and from the other end 60mm.

This change in the market has required the manufactures such as Master Key Systems MKS to ensure they carry a range of offset euro cylinder locks, capable of being Master Keyed.

By far the most specified Euro Cylinder is the Cylinder and Thumb Turn or key & turn. This has key access on the outside, with a thumb-turn on the inside used for locking and unlocking the door lock.

This type of cylinder is an absolute must when fitted to a final exit door in any public or managed spaces or accommodation. As with all other euro cylinder locks, a cylinder with thumb turn comes in a variety of sizes, both equal splits and offsets.

Having established what is required of the system, how it's to work, how many cylinder locks are required, what sizes are required and who is able to open which cylinder locks, the user must decide what level of key and cylinder security is required. This can be a simple open key system whereby the master key holder and individual key holders can get keys cut at a local locksmith or key bar.

This level of key security is very low and should be considered with caution and is more about convenience than security. By and far the most secure for key security is a closed or restricted system. The cylinder lock manufacturer will not issue key blanks and providing the key profile is truly restricted, they will not be available anywhere other than the Master Key System manufacturer.

Find the right master key system for your property by checking out our master key product range.

You can also get in touch with a member of the MKS team today by using our quick and easy contact form below. Alternatively, you can contact our team today on 01902 737 672 or by emailing sales@masterkeysystems.co.uk

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