Cat A vs Cat B Fit Out: What's the Difference and Which One Do You Need?
Published 10 March 2026
If you've started looking into a commercial fit out and keep seeing the terms "Cat A" and "Cat B" thrown around, you're not alone. It is one of the most common questions we get from business owners and tenants across Portsmouth and the South Coast, and the good news is that once you understand the difference, the whole fit out process becomes a lot clearer.
In this guide we will explain what Cat A and Cat B fit outs actually mean, who typically pays for each, and how to work out which one applies to your project.
What Is a Cat A Fit Out?
A Cat A fit out (short for Category A) is the first stage of preparing a commercial space after it's been built or stripped back to a blank shell. It's usually carried out by the landlord or developer, and its purpose is simple: get the space to a condition where it can be handed over to a tenant.
A Cat A fit out typically includes:
- Raised access floors
- Suspended ceilings
- Basic mechanical and electrical services (heating, ventilation, power distribution)
- Fire detection and suppression systems
- Basic lighting
- Toilets and welfare facilities
What it doesn't include is anything specific to how a particular business will use the space. There are no internal walls, no meeting rooms, no kitchen, no branding, just a clean, functional blank canvas.
If you're a landlord preparing a unit to let, a Cat A fit out is what you're aiming for. If you're a tenant moving into a new space, this is what you'll typically inherit before your own works begin.
What Is a Cat B Fit Out?
A Cat B fit out (short for Category B) is where the space gets transformed from that blank canvas into a working environment that reflects your business. This is almost always carried out by the tenant, either directly or through their chosen contractor.
A Cat B fit out typically includes:
- Internal partitioning (offices, meeting rooms, breakout areas)
- Suspended ceilings and specialist lighting
- Flooring — carpet, LVT, vinyl, or specialist finishes
- Kitchen and tea point
- Furniture and storage
- Branding and signage
- Data cabling and AV
- Any bespoke joinery or reception desks
In short, a Cat B fit out turns a generic office shell into your office. It's the stage where your layout, your culture, and your way of working gets built into the space.
Cat A vs Cat B: A Simple Summary
| Cat A | Cat B | |
|---|---|---|
| Who carries it out? | Landlord / developer | Tenant / occupier |
| What does it deliver? | A lettable blank canvas | A fully operational workspace |
| Does it include partitions? | No | Yes |
| Does it include furniture? | No | Usually yes |
| Does it include branding? | No | Yes |
| Who pays? | Landlord | Tenant |
Do You Always Need Both?
Not necessarily. In some cases a tenant moves into a space that has already been fitted out by a previous occupier. Depending on the condition and layout, they may be able to move straight in, or make minor modifications without a full Cat B programme.
In other cases, particularly in older or industrial buildings, the space may be handed over as a Cat A (sometimes called a shell and core), which is even more stripped back than a standard Cat A. This would require additional work before a Cat B fit out could begin.
The best approach is always to have a proper survey carried out so you know exactly what you're starting with.
What About Dilapidations?
It is worth mentioning dilapidations here because they are closely linked. When a lease ends, tenants are often required to return the space to its original condition, which typically means removing the Cat B fit out they installed and reinstating a Cat A standard. This is known as a dilapidations obligation and it is something that should be factored in from the start of any tenancy.
If you are approaching the end of a lease and need dilapidations works carried out, we handle that too, get in touch with our team for a clear assessment.
Which One Do You Need?
Here's a simple way to think about it:
You're a landlord preparing a unit to let? → You need a Cat A fit out
You're a tenant moving into a new space? → You need a Cat B fit out
You're a tenant at end of lease? → You may need dilapidations works to reinstate Cat A condition
You're refurbishing an existing occupied office? → This is typically a Cat B refurbishment
Still not sure? That is completely normal. Most projects do not fit neatly into one box. The best thing to do is have a conversation with a contractor who can look at the space, understand what you are trying to achieve, and give you honest advice on the right approach.
How Commercial Building Solutions Can Help
We're commercial fit out contractors based in Portsmouth, delivering Cat A and Cat B fit outs, office refurbishments, and dilapidation works across Hampshire and the South Coast.
Whether you're a landlord, a business owner, or a managing agent, we'll give you a clear picture of what your project involves, what it's likely to cost, and how we'll deliver it with minimal disruption to your operations.
Get in touch today to arrange a site visit or initial discussion. No obligation, just practical advice from an experienced team.
Common Questions
Is a Cat A fit out cheaper than a Cat B fit out?
Usually, because Cat A covers the base finishes and services only. Cat B adds the partitions, kitchens, furniture and finishes that suit your business, so it depends far more on your design.
Who pays for a Cat A fit out?
Cat A is normally carried out by the landlord before letting. Cat B is normally paid for by the tenant, though this is often negotiated as part of the lease.
Can CBS do both?
Yes. We deliver Cat A, Cat B and the dilapidations work at the end of a lease, so one contractor can look after the space throughout.
Aaron runs CBS projects on site across Hampshire, the South Coast and Sussex, from the first survey to handover, and writes our guides based on what he sees on real jobs.
Related Articles
Looking for more advice on commercial fit outs and office refurbishments? Head over to our Insights & Advice section for more guides, tips and practical information to help you plan your next project.
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