If you are leasing or refurbishing commercial office space, you will almost certainly come across the terms Cat A and Cat B. Understanding the difference between a cat a vs cat b fit out is essential, because it determines who pays for what, what condition the space will be in when you take possession, and how much additional work you need to budget for.
Despite being standard industry terminology, these categories cause confusion for tenants, landlords, and even some property agents. In this guide, we explain exactly what each category covers, who is typically responsible for the costs, and how to work out which type of fit out you need.
What Is a Cat A Fit Out?
A Category A fit out, commonly referred to as Cat A, covers the base build elements that bring a commercial shell up to a standard where it is ready for tenant occupation and customisation. Think of Cat A as the blank canvas. The space is functional and compliant with building regulations, but it is not yet a working office.
A typical Cat A fit out includes the following elements:
Raised access flooring: This provides a void beneath the floor for running power, data, and mechanical services. Raised floors are standard in modern commercial offices and allow for flexibility when the tenant configures their layout.
Suspended ceilings: Usually a grid and tile system that conceals the services above, including ductwork, cable trays, and sprinkler pipework. The ceiling void is a critical part of the building’s servicing strategy.
Basic mechanical services: Heating, ventilation, and air conditioning (HVAC) systems are installed to a base level. This typically means the main plant is in place with primary distribution, but the detailed zoning and terminal units may be left for the tenant to configure during Cat B.
Electrical distribution: Main electrical supply, distribution boards, and basic lighting are included. Power and data outlets are not usually installed at Cat A stage, as their positions depend on the tenant’s layout.
Fire detection and protection: Smoke detectors, fire alarm panels, emergency lighting, and sprinkler systems (where required) are installed to meet building regulations and insurance requirements.
Passenger lifts and common areas: In multi tenanted buildings, the landlord typically fits out the reception, lobbies, stairwells, and lift cars as part of the Cat A works.
Toilet facilities: WCs and washrooms serving the floor or building are usually completed at Cat A stage.
The key point about Cat A is that it provides a serviced shell. You could walk into a Cat A space and see a clean, well lit area with a finished ceiling and floor, but no desks, no partitions, no kitchen, and no meeting rooms. It is the starting point, not the finished article.
What Is a Cat B Fit Out?
A Category B fit out is where the space becomes a functioning workplace tailored to your business. This is the stage where the generic shell is transformed into an environment designed around how your team works.
Cat B works typically include:
Internal partitioning: Creating individual offices, meeting rooms, huddle spaces, and phone booths. This can range from basic stud and plasterboard partitions to full height glazed systems with manifestation and integrated blinds.
Detailed M&E distribution: Running power, data, and comms to individual workstations and rooms. Adjusting the HVAC zoning to suit the new layout, adding supplementary cooling where needed (server rooms, for example), and configuring lighting to suit different areas.
Kitchen and breakout areas: From a simple tea point with a worktop and a few cupboards through to a full staff kitchen with appliances, seating, and informal meeting space.
Reception and entrance design: Creating a welcoming front of house area that reflects your brand. This might include a reception desk, feature wall, signage, and waiting area.
Furniture: Desking, task chairs, storage, meeting tables, soft seating, and breakout furniture. Furniture can be procured separately or as part of the commercial fit out package.
Branding and wayfinding: Applying your company identity throughout the space, from wall graphics and signage to colour schemes and material choices that reflect your brand values.
AV and technology: Screens, video conferencing equipment, room booking systems, digital signage, and wireless presentation tools.
Specialist areas: Depending on your business, this might include laboratories, workshops, training rooms, showrooms, or secure areas with enhanced access control.
The cat a vs cat b fit out distinction is essentially the difference between building the infrastructure and creating the workplace. Both are necessary, but they serve different purposes and are usually delivered by different parties.
Who Pays for What: Landlord vs Tenant
This is where the commercial reality comes in, and where misunderstandings frequently occur.
Cat A costs: In most standard commercial lease arrangements, the landlord is responsible for delivering the space to Cat A standard. This is considered part of the building’s base specification and is reflected in the rent. However, there are exceptions. In some developments, particularly older buildings or those undergoing building refurbishment, the landlord may offer a contribution or incentive rather than delivering Cat A themselves. In other cases, the tenant may negotiate to take on Cat A works in exchange for a rent free period or a capital contribution.
Cat B costs: The Cat B fit out is almost always the tenant’s responsibility. This is your space, configured to your requirements, and you pay for it. The cost varies enormously depending on specification, but it is a significant capital investment that needs to be planned carefully.
Landlord contributions: It is common for landlords to offer a fit out contribution as part of the lease negotiation. This is often expressed as a sum per square foot and can be applied to either Cat A or Cat B works. The amount varies depending on the market, the length of lease, and how keen the landlord is to secure a tenant. Always negotiate this point early and make sure the terms are clear.
Dilapidations: At the end of your lease, you may be required to return the space to its original condition. This means stripping out all Cat B works and reinstating the Cat A specification. The cost of this needs to be considered when planning your fit out. Some tenants opt for a settlement figure with the landlord rather than carrying out the physical work, particularly if the landlord intends to refurbish the space for the next occupant. Our team can advise on property maintenance and end of lease obligations.
How to Assess What You Need
Working out whether you need a Cat A, Cat B, or both depends on the condition of the space you are taking on.
Taking a brand new or recently refurbished space: If the building is new or has been recently refurbished to Cat A standard, you will likely only need a Cat B fit out. Check the Cat A specification carefully against your requirements, as some elements may need upgrading (for example, additional cooling capacity or enhanced power supply).
Taking an older or previously occupied space: If the space has been stripped back to shell by the previous tenant, or if it is an older building that has never been fitted out to modern standards, you may need both Cat A and Cat B works. This is more expensive and takes longer, but it gives you a completely fresh start.
Taking a space with an existing Cat B fit out: Sometimes you can negotiate to take on the previous tenant’s fit out. This can save significant time and money if the layout broadly suits your needs, but be cautious. Inherited fit outs may have hidden issues, and you need to check the condition of M&E services, the age of the systems, and whether the space meets current regulations.
In all cases, getting a professional survey of the space before you commit is strongly recommended. What looks like a Cat A space on the surface may have underlying issues that affect your budget and programme.
Common Confusion Points
Even experienced property professionals sometimes get the cat a vs cat b fit out distinction wrong. Here are the areas where confusion most often arises.
Where Cat A ends and Cat B begins: The boundary is not always clear cut, particularly with M&E services. For example, is the air conditioning zoned to individual rooms at Cat A stage, or is that a Cat B responsibility? Is the lighting layout generic (Cat A) or specific to the tenant’s design (Cat B)? These boundaries need to be agreed in the lease or agreement to lease, and they should be documented clearly.
Shell and core vs Cat A: Shell and core is a step below Cat A. It refers to the structural frame, external envelope, and core services (lifts, stairwells, main risers) but does not include raised floors, ceilings, or distributed M&E on individual floors. If you are taking a shell and core space, you need to budget for Cat A on top of Cat B.
Refurbishment vs fit out: A refurbishment involves upgrading the existing building fabric and services. A fit out involves configuring the internal space. In practice, many projects involve elements of both, particularly in older buildings where the existing infrastructure needs attention before the fit out can proceed.
Who manages the Cat A works: Even when the landlord pays for Cat A, the tenant may want input into the specification, particularly if it affects the Cat B design. In some cases, the tenant manages both Cat A and Cat B as a single project, with the landlord contributing to Cat A costs. This can be more efficient but requires careful contractual arrangements.
Programme Differences
The programme for a Cat A fit out is different from a Cat B project, and understanding this helps with planning.
Cat A works tend to follow a predictable sequence. Strip out (if required), structural works, primary M&E installation, raised floors, ceilings, basic finishes. The duration depends on the size and condition of the space, but for a typical floor of 5,000 to 10,000 square feet, Cat A takes around six to ten weeks on site.
Cat B works are more variable because they depend on the complexity of the design. A simple open plan office with a few meeting rooms might take six to eight weeks. A highly specified space with bespoke joinery, specialist finishes, complex AV, and multiple room types could take 12 to 16 weeks or more.
When both Cat A and Cat B are required, they can sometimes be overlapped to compress the overall programme. This requires careful coordination but can save several weeks compared to completing each phase sequentially.
The design and procurement period before work starts on site also needs to be factored in. Allow four to eight weeks for design development, costing, and contractor appointment, and additional time for any specialist items with long lead times (bespoke furniture, imported finishes, specialist AV equipment).
Getting the Right Advice
The cat a vs cat b fit out question is not just a technical one. It has direct implications for your budget, your lease negotiations, your programme, and the quality of your finished workspace. Getting it wrong at the start, whether by misunderstanding the lease obligations, underestimating the scope of work, or failing to coordinate between the two phases, leads to delays, cost overruns, and a result that does not meet your expectations.
Working with a contractor who understands both categories and can advise on the most efficient approach for your specific situation makes a real difference. Whether you need a straightforward Cat B fit out of a modern space or a complete Cat A and Cat B programme in an older building, the principles are the same: clear scope, realistic budget, good coordination, and experienced delivery.
If you are planning a commercial fit out and want to understand what is involved, contact Ashbarn Construction to discuss your project. We work across Lancashire and the North West, delivering fit out projects of all sizes, and we are happy to carry out a site survey and provide clear, honest advice on scope, cost, and programme.
