Shell and Core, Cat A and Cat B Fit Outs: What Are They and the Differences

Fit outs can be applied to many different spaces, including offices, shopping centres, gyms and other hospitality sectors, helping to transform interiors for the better, aligning business branding with your space and set areas up with optimal functionality. Fit outs can come in three different forms, a Shell and Core fit out, a Cat A fit out and a Cat B fit out. Each type comes with its own levels of building techniques and applications, and we are here to help you understand the differences between them all.

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shell and core fit out

The first type of office fit out is known as a shell and core fit out. This is the most basic type of fit out and involves building the fundamental framework of a building’s interior. The inside space will essentially be an empty shell, with exposed sub-floors and without any lights, heating or air conditioning. From the outside, the building will look complete but, on the inside, it will be rather bare. Think of this fit out like the scenes in Die Hard, with John McClane running around barefoot in the higher levels of Nakatomi Plaza with plasterboards and steel beams lying about the place. These levels are going through a shell and core fit out and will then eventually be fitted out with a Cat A or Cat B type.

Some areas will have very basic utilities and common areas to be shared between tenants. Lifts, toilets, reception areas, stairwells and loading bays can all be a part of a core fit out. However, all other areas will still possess exposed floors and services.

why choose a shell and core fit out?

But if a shell and core fit out just includes the structural foundations and basic shared areas, what’s the point of having one? Well, a shell and core fit out gives the tenants and businesses the opportunity to finely tune and craft a space to suit their specific needs. A shell and core fit out is especially useful for new tenants looking to lease out the space for businesses, who will then come in and choose their next category of fit out – either Cat A or Cat B. This type of fit out is purposeful for real estate development as once the core fit out is at the stage where it is economically viable for the landlord, they can then pass on control to the new tenants who will then hire a fit out contractor to develop the interior space further.

cat a fit out (category a fit out)

The next type of fit out stage is known as a Cat A fit out. Evolving from the shell and core variant, a Cat A offers a functioning space with basic installations and electrical applications, including lighting, fire protection systems, raised floors, suspended ceilings and air conditioning and ventilation (HVAC). While these fittings will be installed, they will only have a basic finish without any colour schemes or dedicated layout.

Category A fit outs are the most popular choice for landlords to perform before they lease the space to new tenants. The main benefit of a Cat A is for tenants to come in a have the freedom to design the layout and functionality of their space with a Cat B fit out. Think of a Cat A as this – it’s an occupiable space with minimal functionality but without purpose.

cat b fit out (category b fit out)

That realised purpose comes in with a Category B fit out. An efficient, functional and purposeful office space that comes with necessary applications and a more bespoke layout and design features. The new tenants will often be the ones to hire specialist fit out contractors to provide them a space that is ready to use. These contractors will include designers, architects and builders who will create a fantastic interior space for businesses, meticulously considering every last detail.

The features that will be installed in an office space during a Cat B fit out include:

Partition walls – to create breakout rooms, offices, meeting rooms and more

Floor and ceiling finishes


IT systems and infrastructure

Lighting fixtures

Branding elements – graphics, signage, bespoke finishes


Fitted kitchens and non-communal office services

Alterations to HVAC systems

All necessary electrical appliances and infrastructure

Category B is the most important fit out type for tenants looking for their workforce to move into and use fully. With a Cat B, the office will be ready to move into allowing business to boom!

the differences between shell and core, cat a and cat b fit outs

The main differences between the three types include the level of completion, the customisation in fit outs and the benefits each fit out type offers to landlords and tenants.

Shell and core comparisons and differences

Shell and core fit out’s level of completion is minimal. This does mean that the level of customisation is the highest, as the blank canvas can be transformed into all manner of layouts and functions. For landlords this is ideal as it requires the least amount of costs and time but with the drawback of being a space that is less attractive to tenants looking to utilise a ready space.

Cat A comparisons and differences

This partially complete fit out type allows for moderate customisation with only basic elements in place. Landlords will benefit more from a Cat A than tenants, as this fit out stage is again less time consuming and this time, easier to lease to potential tenants. Tenants will also have a reduced fit out time, but less customisation compared to a Cat B fit out.

Cat B comparisons and differences

For a whole, complete package, a Cat B fit out is highly worth it for tenants as they can save the most amount of money and time before settling into their new office. For individual businesses and branding purposes, a Cat B is the most customisable and those choosing this type will have to consider all design aspects with the help of professionals. Although it requires a higher initial investment of money and time from landlords, a Cat B fit out makes the location much more attractive to tenants, helping to make a solid return on investment in a short amount of time.

Each level of fit out benefits tenants and landlords differently. From the core fit out all the way to a Cat B, choosing one fit out type over another will depend on various factors, such as the urgency of the occupancy, budget requirements and the level of customisation. Both landlords and tenants need to consider these factors carefully to make a decision that serves their immediate and long-term interests.

office fit outs with vanguard

Each variable of an office fit out requires careful consideration to truly benefit from the process. It’s imperative that landlords make informed decisions on the fit out type when intending to lease out a commercial space, otherwise, the return on investment could be a slow process rather than an efficient one. Vanguard has the expertise and network of contacts to realise your desired office fit out. We are the UK’s number one choice in helping to design and build new, exciting spaces for businesses and landlords in the commercial real estate industry, with all three types of fit outs.

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