Eden News

A building construction site, with two cranes looming overhead. The basic structure or ‘shell’ of the building is being constructed.

20 April 2021

What is a Shell and Core Fit Out?

There are plenty of terms in the construction industry that, for the uninitiated, may be difficult to decipher. Shell and core fit-out is a perfect example of such jargon. To help, we draw on our expertise to cover the following:

  • Shell and core definition
  • What is the difference between shell and core and Cat A?
  • Why have a shell and core fit-out?

Let’s get started.

Shell and core definition

In every construction project where a new structure is erected, the first thing to be built is the basic structure or framework. This is known as the ‘shell’. This includes:

  • The external walls and cladding of the building (also known as the building envelope)
  • The floors
  • The roof

Within the shell, the building’s electrical supply and mechanical infrastructure is put in place. This includes ‘core’ services like:

  • Mains water
  • Gas
  • Electrical services

In many ways, shell and core provisions refer to the basics of a building. That may explain why it’s also called a base build. The building is fully functional but far from move-in ready, with the interior spaces left unfinished for the landlord or tenants to do with as they wish.

An office that has a Cat A fit-out with brown carpeting, panoramic windows overlooking a city, and pillars with plug sockets.
The empty interiors of an office building. Credit: Sergei Wing on Unsplash.

What is the difference between shell and core and Cat A?

In order to explain the difference between shell and core fit-outs and Category A fit-outs, we have to take a step back and first explain what is a fit-out. 

A basic definition is that a fit-out is a term used by construction companies to refer to the interior refurbishment of industrial, commercial or residential spaces, making them suitable for use. For construction companies, fit-outs are a common part of the construction process. But for those enlisting a fit-out professional to provide these services, deciphering the different kinds of fit-out available, and what each entails, is easier said than done.

We already know that core and shell fit-outs involve building the basic framework of a structure. Once the ‘shell’ is complete, the building is ready for a Cat A fit-out where the interiors undergo work and are brought to a ‘white box’ stage – that is, a stage where the space can be handed over for final completion in the form of decoration and furnishing. 

Cat A fit-outs include but are not limited to the following being installed:

  • Flooring
  • Raised flooring
  • Ceiling
  • Suspended ceilings
  • Staircases
  • Mechanical, electrical and plumbing (MEP) 
  • Heating, ventilation, and air conditioning (HVAC)
  • Lift installation
  • Disability Discrimination Act (DDA) compliance
  • Tiling
  • Partitions

The work we did on a listed building in Old Broad Street, London, is a good example of a Cat A office fit-out. That project included the installation of light fixtures and n​ew flooring, and painting internal walls.

Another type of fit-out is a Category B fit-out, which builds on a Cat A fit-out and can involve elements of interior design. You can learn more about the two in our Cat A/Cat B fit-out guide.

Why have a shell and core fit-out?

It’s fair to say that when you opt for a shell and core fit-out, you really are getting the basics. Unlike Cat A and Cat B options, this type of fit-out is far from ready to be occupied.

However, they are becoming increasingly popular, particularly for office lettings. The reason for this is that it allows tenants to put their stamp on the space right back to the brick—quite literally.

Construction providers often provide properties, such as office spaces to Cat A or even Cat B fit-out standards, ready for selling or letting. But due to the variety of tastes of prospective buyers and renters, it’s hard to please everyone. Simply put, the easiest way to overcome this is to let tenants make the decisions on everything needed to get their property ready for purpose.

From ceiling tiles to carpets, it’s now common practice for construction firms to leave these decisions up to the tenant. Often offering a rent-free period to complete the property to habitable standards, shell and core fit-outs are a popular option with those wishing to put their own touch on their space, as it provides a blank canvas that allows them to make all decisions on fit-out elements, from flooring to ceiling, to suit their specific needs and preferences.

View of a single floor of a building in a ‘shell’ state. Construction materials are stacked to one side and a construction worker is standing on a ladder working on the ceiling.
Work by Eden London on a building site in a ‘shell’ state.

Looking for a shell and core fit out contractor?

Are you considering opting for a shell and core fit out for your premises? Ensuring it’s completed to the highest possible standard is vital to the lasting quality of your space. And we can help! 

We’re a fully accredited principal contractor specialising in fit-outs in London and the South East. We have vast experience working in the construction industry and have completed our fair share of shell and core fit-outs. Not only that, we have a 100% track record of completing them on-time and on-budget. Read our case studies to learn more about our work, and contact us to find out how we can help.

“Eden have been incredible from start to finish. They have been entirely transparent on costs, assisted with design and worked extremely hard to meet my tight deadline. I couldn’t recommend them enough and look forward to working with them again on future projects.”  

Marnie Swindells, Bronx