For office tenants and landlords
What are the Different Types of Office Fit Out?
Sviatoslav JerdetchiiCEO & Founder of Craftex. Updated , 6 min read
The short answer
A commercial office fit-out comes in four types: shell and core, Cat A, Cat A+ and Cat B. Most London tenants take a Cat A floor from the landlord and pay for their own Cat B.
- Shell and core is the bare building with shared services.
- Cat A adds ceilings, floors, lighting, air conditioning and fire systems.
- Cat A+ adds furniture, meeting rooms and a kitchen, ready to move in.
- Cat B is your own layout, rooms, finishes, furniture and AV.
Most office leases in London are signed before anyone asks what the floor actually includes. The agent says "Cat A". The tenant hears "ready to use". Then the first commercial office fit-out quote arrives, and nothing on it is optional.
The four types of office fit-out explain that gap. Each one is a stage in how finished the space is, and who pays for it.
This guide explains what each type includes, what it costs in London and how to choose. We design and build offices, so it's written from the contractor's side. Have a floor in mind? Book a site visit and we'll tell you what it really needs.
The four types of commercial office fit-out at a glance
There are no official definitions. Shell and core, Cat A, Cat A+ and Cat B are market conventions. Landlords and agents use them slightly differently, so always check the specification, not the label. Our Cat A vs Cat B comparison goes item by item.
| Type | What you get | Usually paid by | Ready to work in? |
|---|---|---|---|
| Shell and core | Structure, façade, lifts, stairs, toilets, main services to the floor | Developer | No |
| Cat A | Raised floor, suspended ceiling, lighting, air conditioning, fire alarm, basic finishes | Landlord | No, it's an empty floor |
| Cat A+ | Cat A plus furniture, meeting rooms, a kitchen and data | Landlord | Yes, almost at once |
| Cat B | Your layout, rooms, finishes, furniture, kitchen, IT, AV and branding | Tenant | Yes, designed for you |
Shell and core is the building, not an office
A shell and core building is finished outside and in the shared parts. The structure, the façade, the lifts, the stairs and the common toilets are done. The main services reach each floor, but stop there.
Inside, the floors are bare concrete. There are no ceilings, no lighting and no heating or cooling on the floor. Developers sometimes let space in this state to tenants who want full control. It's also where a refurbishment starts when a floor is stripped back.
Taking shell and core space means you fund the base build too. In return, nothing is installed twice.
Cat A is the landlord's empty floor
A Cat A fit-out makes the floor usable but not furnished. It's what most London landlords hand over on a new letting. It usually includes:
- Raised access floors for power and data
- Suspended ceilings
- Lighting on a regular grid
- Air conditioning and ventilation
- A fire alarm and emergency lighting
- Toilets and basic finishes
A Cat A floor is open plan. The ceiling grid, the lighting and the air conditioning are all laid out for a bare floor. Every room you add later changes them.
Why Cat A can waste money
Many tenants rip out part of the Cat A to build their Cat B. New ceilings come down for partitions. Lights and diffusers move. If you're signing early, ask the landlord to skip the Cat A and contribute that money to your Cat B instead. Our guide to landlord fit-out contributions explains how to ask.
We recently hired Craftex for a commercial office fit-out project in Central London, and overall, we’re really happy with the result. There was a delay on our side with a custom glass partition supplier, but the Craftex team managed the construction schedule very professionally and kept everything on track. Their guys worked clean, respected our workspace and IT setup, and kept the site tidy throughout. If you're looking for a reliable office refurbishment company in London, I’d definitely recommend Craftex. Would use them again without hesitation.
Cat A+ is a furnished office you can move into
Cat A+ is a Cat A floor that the landlord furnishes. It usually adds desks and chairs, a few meeting rooms, a kitchen or tea point and data cabling. Some call it "plug and play".
It suits small and growing teams on shorter leases. You move in quickly and spend little up front. The trade-off is control. The layout, finishes and brand are the landlord's, and changing them later costs you.
Cat B is the office built around your team
Cat B is the tenant's own fit-out, on top of Cat A. It turns an empty floor into your office. For ideas, see our expert office design tips. It usually covers:
- Partitions, meeting rooms and focus rooms
- Kitchen, breakout and reception
- Finishes, joinery and branding
- Furniture and storage
- IT, AV, access control and security
- Changes to lighting, air conditioning and fire alarm to suit the rooms
This is where layout decides cost. Each enclosed room needs walls, a door, lighting, ventilation and fire alarm changes. Our guide to the main types of office layout shows what each layout means for the build.
What each type of office fit-out costs in London
The landlord usually pays for shell and core and Cat A. Your budget is the Cat B on top. These are our 2026 rates for a London Cat B fit-out on a Cat A floor, excluding VAT.
| Cost per sq ft | Basic | Mid-range | High spec |
|---|---|---|---|
| Construction | £64 | £86 | £114+ |
| Furniture | £19 | £33 | £55+ |
| AV and IT infrastructure | £5 | £9 | £14+ |
| Total per sq ft | £88 | £128 | £183+ |
The rates assume the Cat A services are in good condition. If the floor is shell and core, or the services need replacing, add the Cat A works. Dilapidations, landlord's consents, IT hardware and VAT come on top. Our office fit-out cost guide has example budgets by office size.
Two Craftex projects at both ends of the scale
Both projects show how much the starting point decides the work.
Beaumont House: a fast Cat B on an existing floor
Beaumont House in High Street Kensington was a run-down 750 sq m office. The client had five weeks left on their old lease. We demolished walls to open up the floor. Frosted glass partitions created meeting rooms.
We replaced the lighting and wiring and ran data under the floor to every desk. We added CCTV, access control and a new kitchen. It was handed over in three weeks with zero snags, for £350K.
Portsoken House: from empty warehouse to finished offices
Portsoken House in Aldgate started as an abandoned warehouse. We fitted out 1,550 sq m over two floors for £2.2M in seven months. The work covered both stages: a full mechanical and electrical package, new ceilings and levelled concrete floors. Then came a new entrance, kitchen and WCs. The rest of the building stayed let throughout.
How to choose the right office fit-out type
Start with the lease and the team, not the finishes. Moving premises too? Our office relocation checklist sets out the timeline. These questions usually decide it.
- How long is the lease? On a short lease, Cat A+ or a light Cat B keeps cost down. On a long one, a full Cat B pays back.
- How different is your team? If you need many rooms or special spaces, Cat B is the only real option.
- When must you move in? Cat A+ is fastest. A Cat B can still be quick if the design is fixed early.
- What will the landlord contribute? Skipping Cat A for a contribution can save money and waste.
- What does the building allow? Check the services, floor loads and the licence for alterations before you design.
Since 1 April 2023, landlords can't keep letting non-domestic property below an EPC rating of E, unless exempt. Ask for the floor's EPC early. Upgrades to lighting and air conditioning often sit inside the fit-out.
Approvals every office fit-out needs
Internal alterations usually don't need planning permission. A listed building needs listed building consent for significant internal works. Most fit-outs still need building regulations sign-off for fire safety, escape routes, ventilation and electrics.
The landlord will also want drawings and method statements before work starts. Our guide to building regulations for an office fit-out covers the detail.
One team from the empty floor to the finished office
Most delays in a commercial office fit-out happen between parties. The landlord's surveyor, the designer, the M&E engineer and the builder all wait on each other. Our office fit-out service puts design and construction under one contract and one programme.
We take on office fit-outs from £100,000 to £10M+. If you're comparing floors or signing a lease soon, book a site visit. We'll check what the landlord is handing over and what your team needs on top.
