The fashion for London office fit-outs: What are the trends and difference in cat A, cat A+ and cat B fit-out?

When it comes to finding new office space and considering its fit out, i.e., the design and building work required; you must consider your Cats.

We aren’t talking furry friends here. In this instance, Cat stands for category and is the classification of a fit out which defines how much of the design and building work is already done before you occupy the new space and what elements are included.

The two most common of these are Cat A and Cat B. However, the classification process isn’t standardised across the industry, which can leave confusion in the fit out process. Therefore, it’s important to be clear about the key aspects and differences so that you can understand which classification might best suit your organisation’s needs.

Understanding the four
classifications of fit out

Although Cat A and Cat B are the most common, they are only two of four classifications. In ascending order of completeness of space, the four include Shell and Core, Cat A, Cat A+ and Cat B.


Shell and Core is a space at its most basic, following construction. It means that the structural elements and literal shell and core of the building – the concrete and metal frame – is complete but the installation of facilities and services such as lighting and air conditioning haven’t yet taken place and as such the space isn’t yet usable by tenants.


Cat A is the finished empty shell of the building but with the installation of mechanical and electrical services and finishes; other services such as lighting and air conditioning, as well as the installation of grid ceilings and a lick of paint. Although it doesn’t include any design elements the crucial building work is complete, and the space is available as a blank canvas for tenants wishing to make the space their own by adding their own touches.


Cat A+ is a more recent development of fit out status which sits between the two categories of Cat A and Cat B. As the name suggests it’s basically an upgraded Cat A fit out that isn’t quite the full design package of a Cat B fitout.

Instead, it includes the functional space required, such as meeting rooms and breakout space, furniture and workstations, kitchens, and IT infrastructure, as well as the services needed. However, it won’t include the full design elements of Cat B. It’s usually requested by the landlord and allows the new tenant or occupier to put their own mark on the space in the future, or more commonly simply take the space and begin work.


Cat B, meanwhile, is the finished product – an office space that also includes the design elements required by the company taking the space. This means that as well as all the functionality required of an office it also includes additional personalisation elements such as partitions and doors, floor finishes, specialist lighting, furniture, and branding. A design and build company will normally assist with this stage of the fit out to ensure the design is tailored exactly to the new tenant’s brief.

Understanding the trends

The hunger for Cat A+

Its readiness to occupy means that a Cat A+ fit out is often referred to as a plug and play space since tenants can begin work immediately. It’s therefore gaining a reputation for being useful in co-working offices or where a tenant might be looking to sublet space. It’s also popular with landlords who offer flexible space under built to lease since it helps secure interest faster. The prospective tenant has a ready-to-go solution rather than having to design themselves, which allows them to move into a functional office space sooner. Yet it still allows them to make their own tweaks to space, as well as add their branding and other personal touches should they so wish. Alternatively, they can leave the space as is, meaning that they can begin work with minimal upfront costs. This makes it particularly well-suited to small businesses for whom the purchase of an office or refurbishment of space is out of reach, or who want their own furnished and functioning workspace rather than sharing in a co-working environment.

The emergence of a new classification – Cat C

As organisations increasingly focus on sustainability and their environmental credentials the idea of ripping out materials and branding every time, they take on new office space can sit uncomfortably with both tenants and landlords. In 2020, the UK government released its Circular Economy Package: Policy Statement, presenting a new legislative framework for the construction industry to reduce waste. Although it encourages circular strategies in building there is yet no guidance for the complete built environment.

According to Envision there is a circularity gap when considering the leasing of office and retail buildings. It suggests that even if a new or refurbished building is designed to implement core circular principles, then there could be 11 new fitouts within the lifespan of the building if it has a typical lease length of five years, over a 60-year lifespan. This, in itself, would contribute an estimated 800,000kg of CO2 over its lifecycle, the company claims. This has led to the suggestion of a fifth fit out classification option – Cat C.

This is a category based on circularity and would be the equivalent of a Cat B fit out but without the addition of brand-specific material and décor and therefore without the carbon-intensive removal of materials and branding each time an old tenant leaves and a new tenant moves in.

The concept would not only reduce the frequency of fitouts but also have greater consideration of the original installation of the materials and methods of installation used as well as be able to be recycled or reused in future fitouts. Its creation, provision and maintenance would be the responsibility of the landlord.

Essential workspace guide

How to achieve fit-out success

Our essential guide will open the door to thinking in new ways about how to approach planned office fit-outs. Our internal team of consultants, designers and builders have identified best practices to ensure your office fit-out is a success. Whether you’re experienced in the fit-out process, or this is your first time, this step-by-step guide will help you navigate the key steps ahead on your journey to transforming the office into workspace fit for the future.

Download now

Tell us what you need

Download our selection of guides and checklists to help you make informed decisions at every step of your office relocation or refurbishment journey.

    The information provided will be used by the Nativspace to provide the requested feedback. Your address or email will not be transmitted to any other organisation.