Date: September 29, 2023 10:50 am

What is a Cat A and Cat B Fit Out?

What is a Cat A and Cat B Fit Out?

Electrical infrastructure installation

Electrical fit outs are an essential aspect of any building construction or renovation project, ensuring that a building has a safe and energy efficient electrical infrastructure is critical. Two commonly used terms for the electrical fit out of commercial and residential buildings are “Cat A” and “Cat B.” These categories each require different levels of design and installation.

Defining Cat A and Cat B fit out

Cat A (Category A): Cat A is often referred to as the ‘blank canvas’, as it provides the basic generic infrastructure of a building. It refers to the initial phase of an electrical fit out, focusing on the essential infrastructure required to make a commercial or residential space functional. This phase typically includes basic electrical wiring, power distribution, lighting, and safety measures.

Cat A is often considered the ‘shell and core’ phase, where the emphasis is on creating a blank canvas for future occupants. This is often how a building is provided by the developers, allowing the new owners or tenants to customise the spaces to meet their individual needs.

What’s usually included in a Cat A fit out:

    • Raised floors and suspended ceilings (with a basic finish)
    • Internal walls
    • Basic mechanical and electrical services
    • Fire detection services and smoke alarms
    • Basic air-conditioning and ventilation (HVAC)
    • Basic internal finishes
Cat A fit out at a warehouse

Cat A fit out at a warehouse


Cat B (Category B): Cat B, on the other hand, represents the more detailed and customised phase of a building and the electrical fit out. This stage involves tailoring the electrical infrastructure to meet the specific needs and requirements of the occupants. It includes tasks such as installing power outlets, data cabling, specialised lighting and control sensor and systems, HVAC controls, and any other electrical systems necessary for the space’s intended use.

Cat B fit out is the next level, and generally includes:

    • Partitioning, for meeting rooms, offices and break-out areas
    • Fully fitted kitchens
    • Reception areas
    • Carpeting and flooring to suit space requirements
    • Tailored lighting fittings and systems
    • Kitchen facilities
    • Office furniture
Cat B fit out at a warehouse

Cat B fit out at a warehouse


The Electrical Engineering Installations – Cat A and Cat B

In tangent to the Cat A and Cat B building fit outs, is the electrical engineering installations. The Cat A and Cat B electrical engineering fit outs refer to the following:

Cat A electrical fit out:

This includes the installation of the basic electrical infrastructure required for a Cat A building fit out:

  • Main electrical panels
  • Distribution boards
  • Lighting circuits
  • Power circuits
  • Emergency lighting circuits

Cat B electrical fit out:

This includes the installation of all of the electrical equipment and wiring that is specific to the tenant’s needs. The installation can vary depending upon what the spaces are being used for, who will be using them and for what activities. Cat B may include the following:

  • Power sockets located to suit the tenants requirements
  • Lighting, which will be specific to suit the space and usage
  • Lighting sensor systems
  • Lighting systems which in focus on colour tone
  • IT and audio-visual equipment wiring
  • Security systems – CCTV
  • Access control systems
  • Outdoor lighting
  • Electrical vehicle charging points and systems
  • Solar panels

Transforming the blank canvas of a Cat A area into a functioning Cat B space, needs careful consideration beforehand, to ensure the electrical infrastructure and mechanical installations meets the operational requirements.

Cat B will be tailored to meet the individual needs of the occupant. Consideration is needed on where workstations will be located, meetings rooms, break-out areas and any possible manufacturing or work processes are to be installed. Each different space usage will need the correct electrical infrastructure designed and fitted to ensure the finished areas meet the functions of each space and the people using them.

Electrical engineers play a vital role in both Cat A and Cat B fit out projects. They are responsible for designing and installing the electrical infrastructure that will safely and efficiently power all the building’s systems and equipment.

The General Elements of Cat A and Cat B

Scope of Work: Cat A primarily deals with the foundational electrical work needed to bring a space to a basic operational level. Cat B, on the other hand, focuses on the finer details and customisation based on the tenant’s preferences and specific requirements.

Timing: Cat A is typically completed before a tenant occupies the space. Cat B comes into play once a tenant has signed a lease or decided on the layout and design of their workspace.

Budget: The budget for Cat A work is often borne by the building owner or developer, as it is necessary to make the space leasable. Cat B work is usually funded by the tenant, who wants to tailor the space to their specific needs.

Flexibility: Cat B work offers a high degree of flexibility, allowing tenants to design their electrical fit out to align with their business operations and branding.

Regulations: Both Cat A and Cat B electrical fit outs must comply with local building codes and safety regulations. However, Cat B work may involve additional compliance measures due to the customization involved.

Typical examples what electrical engineers could be involved with for a Cat A and Cat B fit out:

Cat A electrical fit out: Designing and installing the main electrical panel for a new office building. It is also the responsible of the electrical engineers to install the distribution boards that distribute power to the different areas of the building.

Cat B electrical fit-out: Lighting system design, layout and installing the power sockets and lighting infrastructure systems for the office and / or manufacturing space. The electrical engineers will also often be responsible for wiring up the IT and audio-visual equipment.

Electrical engineers play an important role in ensuring premises operate safely, efficiently, and effectively.

Understanding the needs to meet individual requirements

Understanding the distinction between Cat A and Cat B in electrical fit outs is crucial for developers, building owners and tenants. With the knowledge of what Cat A and Cat B, it helps planning and budgeting for the different stages, ensuring that the final space is not only functional but also tailored to meet the specific needs of the occupants.

Whether you’re a property developer, tenant, or project manager, being well-versed in these categories is essential for a successful electrical fit out and creating a suitable finished serviced area.

Gilks have over 60 years of experience, working in a range of industries, covering the different stages of fit outs for various commercial buildings. From office spaces, to care home, educational establishments to warehousing distribution facilities and manufacturing plants.

Through our vast amount of expertise, knowledge and experience, we can support you in creating a space that will suit all your operational needs.

If you would like further information and assistance with your new build or refurbishment project, talk to our team of experts to support your next project.

T: 01270 625 520 |  E:  |


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