The Difference between Shell & Core, Cat A, Cat B, Cat A+ Fitouts


What is office fit out?

An office fit out is the complete process making the interior space suitable for purpose and occupation. This process is made up of several different factors, including electrical, mechanical, decoration and office furnishings, that make it a working space. 

New office spaces will often be provided by the landlord or developer as a Shell and Core, or Cat A space. In short, this means that it is a blank canvas, leaving the tenants to transform the space into their workspace through what we call a Cat B fit out. 

In this blog we take you through the different terminology, what it means, and what you can expect in each type of space.

What is meant by ‘shell and core’?

A shell and core space only has the base building framework completed. The envelope will be complete, but the inside space will still be an empty shell, with exposed sub-floor and soffit, and all services terminated at the point of entry into the space.

However, communal ‘core’ areas such as lifts, shared toilets and the reception, are usually finished to a high standard and are ready for incoming tenants. 

Usual features of a shell and core space:

  • Lobbies
  • Lift shafts
  • Loading bays

What is a Cat A space?

A Cat A space will provide a basic level of finish above that provided in a Shell and Core space. This would be the space that the landlord would usually lease, but the specific layout, design and finishes are left to the tenant to install. In some cases, the landlord will require the space to be returned to a Cat A condition at the end of the tenancy.

Usual features of a Cat A fit out:

  • Raised floors and suspended ceilings
  • Basic mechanical and electrical services
  • Fire detection services and smoke alarms
  • Air-conditioning and ventilation (HVAC)
  • Basic internal finishes

Cat A spaces provide a blank canvas for designers to dream up a workspace that suits the tenant, including features such as breakout areas, meeting rooms, collaboration centres and wellbeing spaces, which will be installed in a Cat B fit out.

View Example: Ashton House Case Study

What is a Cat A+ fit out?

A Cat A+ fit out is a newer idea in the design and build industry. It is a midpoint between a Cat A and Cat B fit out; a plug-and-play setup, provided by landlords, meaning that a tenant can move in with not much more than their own staff and belongings!

A landlord may fit out only some areas of the building to a Cat A+ standard, to attract smaller tenants who are looking to avoid a long-term investment into a customised Cat B fit out, or to show other potential tenants an example of what their space could look like. 

Dependent on the size of the development and the landlord, Cat A+ spaces are often complemented by increased communal spaces which tenants can use, making it more of a campus-style workplace, and giving a mix of personal office space and co-working spaces or breakout areas. This is particularly popular since the advent of co-working spaces and serviced offices, and the desire to have the ability to work more flexibility, thus giving the landlord further chance of securing tenants in their development if they provide this level of fit out.

What is a Cat B fit out?

Category B fitouts are the finished space that you can move into and use immediately. They are usually left to the tenant to design and install, and therefore will likely align with the brand of that tenant. 

Category B fit outs are ideally tailored to the individual needs of your business, and workforce; it is essential to ensure there is the right mix of space typologies available including collaboration centres, private call and video booths, and focus areas, to enable employees to work in the space they need to get the job done in the best way. 

A tailored Cat B fit out is usually a product of space planning and workplace consultancy, before any design work is completed in order to understand how employees are currently using their existing workspaces, and what changes they would like to see made. This ensures that the new design suits the workforce perfectly, and complements the brand values and company culture. 

Your workspace should reflect your brand, culture and values. This can be achieved in many different ways, through furniture, colour palettes, graphics, and many other custom design elements. It is critical that your office will attract and retain your most valuable asset: your people.  

Usual features of a Cat B fit out:

  • Partitions and doors
  • Floor finishes
  • Specialist lighting and facilities
  • Cafes teapoints and kitchen areas
  • Furniture
  • Branded material and decorations

View Examples:

CAE Technology Services, Hertfordshire

Ocado, Hertfordshire

Engie, Hatfield

Groupe Renault, Hertfordshire


If you are a landlord looking for a company to fit out a space or spaces we’d love to hear from you. Get in touch.