Cat A vs Cat B Office Fit-Out in London: A Complete Guide for Landlords, Operators and Tenants
- Apr 27
- 11 min read
By Mayfair Interiors — London's commercial fit-out and refurbishment specialists. We deliver Cat A infrastructure, Cat B full fit-outs, and live office refurbishments across Central London and the South East.
Quick Answer:
What Is the Difference Between Cat A and Cat B?
Cat A fit-out is completed by a landlord or developer. It brings a raw commercial space to a functional, lettable standard — with mechanical and electrical systems, suspended ceilings, raised floors, and fire safety installed, but no furniture, partitioning, branding, or bespoke finishes.
Cat B fit-out is completed by the tenant or operator. It transforms the Cat A space into a fully operational, branded workplace — with meeting rooms, kitchens, floor finishes, joinery, AV, and everything required to actually work there.
Think of it this way:
Cat A is the landlord's investment to attract a tenant. Cat B is the tenant's investment to make the space their own.
Cat A+ is a third category, growing in popularity in London. It adds furniture, basic partitioning, and connectivity to a Cat A space — giving landlords a 'plug and play' product that lets them compete with flexible and coworking operators.
Who Should Read This?
This guide is written for the people who commission and pay for office fit-out work in London:
•      Landlords and property managers with void office space to make lettable
•      Serviced office and managed workspace operators fitting out new locations
•      Tenants taking a direct lease and commissioning their own Cat B
•      Property developers refurbishing commercial stock
•      Retail and hospitality brands fitting out new sites in London
If you are looking for a fit-out contractor in London to deliver this work, this guide will help you understand what you need — and you can book a free site survey with Mayfair Interiors at any point.
Cat A Fit-Out:
What It Is
What It Costs
When You Need It
What Is Included in a Cat A Office Fit-Out?
A Cat A fit-out covers the essential building services and base finishes that make a commercial space safe, functional, and ready to market to tenants.
Typical Cat A scope includes:
•      Raised access flooring
•      Suspended ceiling grid with recessed lighting — usually LED
•      Mechanical and electrical (M&E) infrastructure: HVAC, ventilation, power distribution
•      Fire detection, alarm systems, and suppression where required
•      Perimeter trunking for power and data
•      Basic welfare facilities — toilets, hand washing
•      Internal walls plastered and painted to a neutral finish
•      Building lobby, lift, and core areas (in full building refurbishments)
Cat A does not include furniture, internal partitions, meeting rooms, kitchens, branded finishes, or AV. The space will look clean and functional in photos but is not yet a workplace anyone could move into and use.
How Much Does a Cat A Fit-Out Cost in London?
Cat A fit-out costs in London typically range from £35 to £75 per square foot, depending on:
•      Building age and condition of existing M&E infrastructure
•      Ceiling height and specification (standard grid vs. exposed services)
•      Floor plate size — larger floors attract better rates per sq ft
•      Location and site logistics — central London commands a premium
•      Programme urgency — fast-track work costs more
Older Central London office buildings — pre-2000 stock with legacy systems — tend to sit at the upper end. New-build or recently stripped shells are more straightforward and generally cheaper to bring to Cat A standard.
How Long Does a Cat A Fit-Out Take?
•      Small floor plate (under 3,000 sq ft): 6–10 weeks on site
•      Single full floor (5,000–10,000 sq ft): 10–16 weeks on site
•      Multi-floor or full building: 16–28 weeks on site, depending on phasing
These timelines assume vacant possession. Live building works — where other floors remain occupied — require phased programmes and out-of-hours working, which extends the overall programme.
Mayfair Interiors specialises in phased, live-building fit-out and refurbishment.
We've delivered Cat A upgrades in occupied Central London buildings where dust containment, noise management, and zero disruption to other occupants were non-negotiable.
Cat B Fit-Out:
What It Is
What It Costs
Who Needs It
What Is Included in a Cat B Office Fit-Out?
Cat B fit-out takes a Cat A (or Cat A+) base and transforms it into a fully operational workplace.
The full scope of a Cat B project typically includes:
•      Internal partitioning: glass, solid, or demountable partition systems
•      Meeting rooms, private offices, and collaboration areas
•      Reception design and bespoke feature joinery
•      Kitchen and break-out area fit-out
•      Floor finishes: carpet tiles, LVT, polished concrete, hardwood
•      Wall treatments, feature walls, acoustic panelling
•      Signage and brand graphics
•      Furniture and workstation installation
•      AV integration, server rooms, structured cabling and data infrastructure
•      Lighting design and bespoke feature lighting
•      Specialist rooms: wellness, podcast studios, client suites
A Cat B fit-out is designed to be move-in ready. When done well, it should reflect the company's culture, support the way the team actually works, and make an impression on every client and employee who walks through the door.
How Much Does a Cat B Fit-Out Cost in London?
Cat B fit-out costs in London vary more than any other category, because specification can range from functional to exceptional:
•      Entry level (open plan, basic kitchenette, standard partitioning): £45–£65 per sq ft
•      Mid-range (designed layout, feature reception, quality finishes): £65–£95 per sq ft
•      Premium (bespoke joinery, high-spec AV, acoustic design, feature lighting): £95–£130+ per sq ft
Serviced office and managed workspace operators — who need every square foot to generate revenue — typically work at the mid to premium end. The fit-out is not an overhead; it is the product they are selling.
Professional fees (designer, M&E consultant, project manager) typically add 12–18% on top of construction costs. Furniture, if procured separately, is additional.
How Long Does a Cat B Fit-Out Take in London?
•      Basic to mid-range, single floor: 8–14 weeks on site
•      Premium or complex specification: 14–22 weeks on site
•      Large multi-floor operator fit-out: 20–32 weeks, depending on phasing
Design and approvals (landlord consent, planning where required) sit before the on-site programme and can add 4–12 weeks to the overall project timeline. Engaging a fit-out contractor early — ideally during design — compresses this significantly.
At Mayfair Interiors, we work alongside designers from early stages. That means programme, buildability, and cost are factored in before the design is finalised, not discovered once work starts.
Cat A+: The Fitted Office and Why London Landlords Are Investing in It
What Is a Cat A+ Office?
Cat A+ — sometimes called a 'fitted', 'plug and play', or 'ready to occupy' office — sits between Cat A and Cat B. It's a landlord-funded investment that goes beyond base Cat A to offer a move-in-ready product.
A typical Cat A+ specification includes:
•      Furniture and workstations pre-installed to a neutral standard
•      Meeting rooms already partitioned with AV ready to connect
•      A kitchen and break-out area fitted and operational
•      Connectivity infrastructure in place — structured cabling, patch panels
•      Considered interior design: lighting, wall finishes, flooring — not generic
Why Are Landlords Choosing Cat A+?
The London office market has fundamentally shifted. Flexible and coworking operators — WeWork, IWG, Industrious, Canvas Offices, and dozens of boutique alternatives — have set a new standard for what an immediately available office can look and feel like.
Traditional Cat A space, shown as an empty shell, struggles to compete on first impression. Cat A+ changes that.
It allows landlords to:
•      Let faster — reducing void periods and associated holding costs
•      Attract SMEs and scale-ups who lack the capital for a Cat B project
•      Command higher rents justified by the quality of the product
•      Compete directly with managed and coworking operators for shorter-term occupiers
Cat A+ is not a compromise. Done properly, it's a genuinely desirable product for a specific and growing segment of the London office market.
We've delivered Cat A+ fit-outs for operators and landlords looking to let faster and attract occupiers who want an independent space without the capital commitment of a full Cat B. If you're considering this route, speak to us before you finalise the brief
Who Commissions Each Type of Fit-Out in London?
Landlords and Property Companies
Landlords typically commission Cat A — and increasingly Cat A+. The goal is a marketable space that photographs well, shows well, and satisfies the broadest possible pool of prospective tenants.
The most sophisticated landlords are also engaging fit-out contractors during the design phase of Cat A, with an eye on avoiding waste when the incoming tenant commissions their Cat B. If the tenant is known, skipping Cat A and going direct from shell to Cat B (with a landlord contribution) is often the most cost-efficient and sustainable approach.
Serviced Office and Managed Workspace Operators
Operators like Canvas Offices, WeWork, Industrious, and boutique managed space providers typically take a shell or Cat A space and commission a full Cat B fit-out. Sometimes they go direct from shell to Cat B, bypassing Cat A entirely.
Their fit-out is not just a workplace — it's the product they sell. Every decision, from the height of the partitions to the quality of the kitchen tap, is a commercial decision. Members and tenants will judge the space the moment they walk in, and they will keep judging it every day they work there.
We understand this model. We've delivered fit-outs for serviced office operators in Central London — at Holborn, Chancery Lane, and across the West End — where the specification had to be right, the programme had to land, and the finish had to hold up to intensive daily use.
Tenants Taking Direct Leases
In a conventional lease, the tenant takes a Cat A space and commissions their own Cat B. The scope and cost are the tenant's responsibility — though the lease often includes a landlord contribution (cash or rent free period) to offset fit-out costs.
For tenants, the most important decisions are made before the contractor is appointed: what do we actually need from this space, what does our design enable, and how do we hold the budget without compromising on what matters?
We work with tenants directly — reviewing design intent, advising on buildability and cost, and delivering the fit-out. Clients who bring us in during design consistently get better outcomes than those who appoint us after the design is fixed.
Retail, Beauty, and Hospitality Brands
Retail and hospitality fit-outs use different terminology but the same principle applies: shell to trading standard. The stakes are often higher — a retail space that doesn't convert customers on day one is already failing.
We've worked with retail and beauty brands in Mayfair and the West End where brand precision, customer flow, lighting design, and the quality of every visible surface are central to the brief. The finish is the brand. There is no margin for anything less than right.
Sustainability: The Challenge with Cat A and What to Do About It
The Cat A model has a sustainability problem. Landlords invest in raised floors, ceilings, and M&E — then incoming tenants strip them back to meet their own Cat B brief. Materials go to landfill. Carbon is spent twice. It is an industry-wide issue that serious clients are increasingly asking contractors to help solve.
Practical approaches that reduce waste without sacrificing quality:
•      Go directly from shell to Cat B with the incoming tenant — eliminating redundant Cat A work
•      Retain and adapt existing infrastructure from previous tenants wherever structurally sound
•      Specify Cat A+ so what's installed is what the tenant will actually use
•      Source reclaimed and recycled materials for finishes where specification allows
We can advise on the most sustainable approach for your building and tenant profile — and help you evidence those decisions to occupiers for whom ESG credentials are a lease requirement.
About Mayfair Interiors
Mayfair Interiors is a London-based construction and fit-out company delivering commercial, retail, and residential projects across London and the South East.
Our commercial work includes:
•      Cat A infrastructure fit-outs for landlords and developers
•      Cat B full fit-outs for serviced office operators, tenants, and businesses
•      Phased live-office refurbishments in occupied Central London buildings
•      Retail and hospitality fit-outs in Mayfair, the West End, and City of London
•      Cat A+ fitted office delivery for landlords competing in the flexible market
Our Clients Include:
We have delivered projects for Canvas Offices — including locations at 1 Fetter Lane, Chancery Lane and 175 High Holborn — as well as retail and beauty brands operating in Mayfair and London's West End.
Why Clients Choose Mayfair Interiors:
•      We work in live buildings. Phased delivery, out-of-hours scheduling, dust and noise control, and safe segregation are things we've built genuine expertise in — not promises we make at tender stage.
•      We are honest about programme and cost from the start. Clients who've been burned by contractors who under-quote to win work and overrun to make margin come to us for a different experience.
•      We deliver the full scope. M&E, ceilings, partitions, floor finishes, joinery, AV rough-in, aftercare — managed by our team, not subcontracted and forgotten.
•      We understand operators. If your fit-out is your product — as it is for every serviced office and managed workspace operator — we understand what that means for the brief, the programme, and the finish.
•      We are London-based. We know how buildings behave in this city, how planning works, how landlords think, and what your tenants and customers will expect.
Frequently Asked Questions
Who pays for Cat A fit-out?
The landlord or developer. Cat A is the landlord's cost to make the space lettable. It is not recoverable from the tenant unless agreed as part of lease negotiations.
Who pays for Cat B fit-out?
The tenant. In some lease agreements, the landlord contributes a capital sum — or grants a rent-free period — to offset the tenant's Cat B cost. This is common in longer leases where the landlord benefits from a higher-specification space at lease end.
Can you go straight from shell to Cat B?
Yes. Going directly from shell to Cat B — bypassing Cat A — is more common in London than many people realise, particularly where the incoming tenant is known before Cat A works would start. It avoids material waste, reduces overall programme, and often results in a better-quality finish because every decision is made for the actual occupier, not a hypothetical one.
How much does a Cat B fit-out cost per square foot in London?
In London, Cat B fit-out costs typically range from £45 to £130+ per square foot depending on specification. Basic functional offices sit at the lower end; premium occupier and serviced office fit-outs sit at the higher end. These figures exclude professional fees and furniture.
What is Cat A+?
Cat A+ is a landlord-funded fitted office — a step beyond Cat A — that provides furniture, partitioned meeting rooms, a kitchen, and connectivity infrastructure, making the space move-in ready for tenants who don't want the cost or disruption of a Cat B project.
How long does an office fit-out take in London?
Cat A fit-outs typically take 6–20 weeks on site depending on scale. Cat B fit-outs take 8–22 weeks on site. Design and approval phases — before site works begin — can add a further 4–12 weeks. Phased delivery in occupied buildings extends these timelines.
What is the difference between a fit-out and a refurbishment?
A fit-out typically refers to works in a new or empty space — building it out from shell or Cat A to occupiable standard. A refurbishment refers to upgrading or reconfiguring an existing, previously occupied space. In practice, many commercial projects involve elements of both.
Do I need planning permission for an office fit-out?
Internal fit-out works in commercial buildings generally do not require planning permission. However, changes to external appearance, listed buildings, changes of use, or works in conservation areas may require consent. Landlord approval is almost always required regardless of planning.
Book a Free Site Survey
If you have a space to fit out or refurbish, or you're not yet sure what you need, we'd like to help.
We offer no-obligation site surveys across London. We will assess your space, understand your brief, and give you an honest view of what the project involves, what it will cost, and how long it will take — before you commit to anything.
Book your free site survey or to learn more about our work.
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Mayfair Interiors — London's Commercial Fit-Out and Refurbishment Specialists.