---
title: "Cat A vs Cat B Fit Out: Differences, Costs & Who Pays"
description: "Cat A vs Cat B office fit-out explained: what each includes, shell and core and Cat A+, typical London costs per sq ft, who pays, and how long each takes."
canonical: https://officerefurbishmentlondon.com/guides/cat-a-vs-cat-b-fit-out
last_updated: 2026-10-04
---

# Cat A vs Cat B Fit Out: What’s the Difference?

By Office Refurbishment London. Published 4 October 2026. Last updated 4 October 2026.

Short answer

## What is the difference between Cat A and Cat B?

Cat A is a finished but empty office floor, usually provided by the landlord, with raised floors, ceilings, lighting, air conditioning and fire systems. Cat B is the tenant’s own fit-out, such as partitions, meeting rooms, kitchens, furniture and IT. London Q1 2026 benchmarks put Cat A at £60–£95 per sq ft and standard Cat B at £120–£200.

**Shell and core** is the bare building: the structure, common parts and main services, with the office floors left unfinished. Cat A and Cat B are the fit-out stages that follow.

If you are taking new office space, you will hear agents, landlords and contractors talk about “Cat A” and “Cat B”. The terms describe how finished a space is, and they matter because they decide what you get from the landlord, what you pay for yourself, and how long it takes to move in. This guide explains the categories in plain English.

**Key takeaways**

- Shell and core is the bare building; Cat A is a finished but empty floor; Cat B is the tenant’s fit-out that makes it work.
- Cat A is usually provided by the landlord; Cat B is usually paid for by the tenant.
- Cat A+ (“plug and play”) adds meeting rooms, kitchens and furniture so you can move in quickly.
- London benchmarks for Q1 2026: Cat A £60–£95 per sq ft, Cat B standard £120–£200.

## Shell and core

Shell and core is the building structure with its common parts: the frame, external walls, roof, lifts, stairs, reception and toilets in the core, and main building services brought to each floor. Office floors are left unfinished: often exposed concrete, no ceilings and no internal distribution of heating, cooling or lighting. Developers sometimes leave space like this so incoming tenants can design it themselves.

## What does Cat A include?

Cat A turns shell and core into a usable, open-plan floor. It typically includes:

- Raised access floors for power and data.
- Suspended ceilings, or an exposed finished soffit.
- Air conditioning and ventilation distributed across the floor.
- General and emergency lighting.
- Fire detection and alarm systems.
- Basic finishes to walls, and toilets in the core.

A Cat A floor is clean and functional but empty: no meeting rooms, kitchens, desks or company identity.

## What does Cat B include?

Cat B is the fit-out that makes the space work for a particular business. It typically includes:

- Partitioned offices, meeting rooms and phone booths.
- Kitchens, tea points and breakout areas.
- Floor finishes, decoration and branding.
- Changes to lighting, air conditioning and power to suit the new layout.
- IT, AV and security systems.
- Furniture, storage and reception.

## Cat A+ and “plug and play”

Cat A+ sits between the two. The landlord goes beyond Cat A and adds a basic fitted layout, often meeting rooms, a kitchen, flooring and sometimes furniture and connectivity, so a tenant can move in with minimal work. It is popular with smaller occupiers and those who want to avoid managing a fit-out, at the cost of less control over design.

## Side-by-side comparison

|  | Cat A | Cat A+ | Cat B |
| --- | --- | --- | --- |
| Usually paid for by | Landlord | Landlord (reflected in rent) | Tenant |
| Ready to work in? | No: empty floor | Largely yes | Yes |
| Design control | Landlord standard | Limited | Full |
| London cost per sq ft (Q1 2026) | £60–£95 | £95–£140 | £120–£200 standard; £220–£380+ premium |

## Who pays for what?

In a typical new letting, the landlord delivers Cat A and the tenant pays for Cat B. That split is negotiable. Landlords sometimes offer a capital contribution or rent-free period towards the tenant’s fit-out, or deliver Cat A+ space to attract occupiers. Where a tenant plans to rip out parts of the Cat A to build a Cat B layout, such as replacing ceilings, some tenants negotiate a payment from the landlord instead of works that will be wasted. Agree the details in heads of terms before you sign.

## How long does each take?

Cat A is usually complete before you sign or take occupation. Cat B timing depends on size and complexity, but even a simple fit-out needs time for design, landlord approval and procurement before work starts on site. For larger floors, several months on site is common. Cat A+ can allow occupation within weeks.

## What is Cat C?

You may occasionally hear “Cat C”. It is not a formal industry standard, but some contractors use it for specialist elements added on top of Cat B, such as server rooms, secure areas or high-specification AV.

## Common misunderstandings

Definitions are not perfectly standardised, so one landlord’s Cat A may differ from another’s. Some include a basic tea point; some use exposed services rather than suspended ceilings. Always ask for the specification in writing rather than relying on the label, and check the condition and capacity of the services, particularly cooling and power, against the layout and headcount you plan.

## Dilapidations: think about the end of the lease

Whatever you install in Cat B, your lease may require you to remove it and reinstate the space to its Cat A condition when you leave. That reinstatement cost (dilapidations) can be substantial, so factor it in when planning your fit-out and negotiating your lease.

## Questions to ask your agent or landlord

- Exactly what does the Cat A specification include, and what condition are the services in?
- Is there a capital contribution or rent-free period towards our Cat B fit-out?
- Can parts of the Cat A that we won’t use be omitted in exchange for a payment?
- What are the building’s rules on working hours, deliveries and contractor approval?
- What will our reinstatement obligations be at the end of the lease?

## Which should you choose?

If you want a space designed around your team and brand, a Cat A floor plus your own Cat B gives you full control. If speed and simplicity matter more, Cat A+ may suit. For an existing office, a refurbishment can achieve much of what a Cat B delivers without moving. To compare options, read our [fit-out cost guide](https://officerefurbishmentlondon.com/guides/office-fit-out-cost-per-sq-ft-london), or [send us your brief](https://officerefurbishmentlondon.com/#enquire) and we will help you scope the project. See also [office refurbishment in London](https://officerefurbishmentlondon.com/).

## Frequently asked questions

### What does Cat A mean in construction?

Cat A is a finished but empty office floor with raised floors, ceilings, lighting, air conditioning and fire systems, ready for a tenant’s own fit-out.

### Is Cat B fit-out paid by the tenant?

Usually, yes. The landlord typically provides Cat A and the tenant pays for Cat B, though landlords may contribute through capital payments or rent-free periods.

### What is a Cat C fit-out?

It is not a formal standard, but some contractors use it for specialist additions beyond Cat B, such as server rooms or secure areas.

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

Shell and core is the bare structure with common parts and main services; Cat A adds finished floors, ceilings, lighting and air conditioning across the office floor.

## Related guides

- [Office Fit Out Cost per Sq Ft in London (2026)](https://officerefurbishmentlondon.com/guides/office-fit-out-cost-per-sq-ft-london)
- [How to Choose an Office Fit Out Company in London (2026)](https://officerefurbishmentlondon.com/guides/choosing-office-fit-out-company-london)
- [Cat A Fit Out in London: What’s Included and What It Costs (2026)](https://officerefurbishmentlondon.com/guides/cat-a-fit-out-london)
- [Office Dilapidations in London: A Tenant’s Guide](https://officerefurbishmentlondon.com/guides/office-dilapidations-london)
- [Office fit-out and refurbishment across London: areas we cover](https://officerefurbishmentlondon.com/london-areas)

Next step

## Planning an office fit-out?

Send us your brief and we will be in touch to arrange a survey and a detailed, no-obligation quote.

[Request a quote](https://officerefurbishmentlondon.com/#enquire)