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

Understanding the difference between CAT A and CAT B fit outs – determines your budget, timeline, and what infrastructure you’re getting versus what you’ll need to fund yourself.

CAT A fit out is the base infrastructure – raised flooring, suspended ceilings, basic M&E, toilets. A blank canvas ready for customisation. This is what the landlord provides as part of the lease agreement.

CAT B fit out transforms that blank canvas into your functional office space, healthcare facility, or commercial workspace with partitions, furniture, branding, and operational fit-out. This fit-out project is typically tenant-funded.

The gap between the two creates most budget surprises. We’ve worked with clients who assumed their new office space included furniture, only to discover £100,000+ in unexpected scope for their office move or office relocation. Similarly, we have seen clients instruct design for new feature lighting within their space, only to find clashes with existing installations, requiring strip-out and creating abortive costs.

What is a CAT A Fit Out?

CAT A fit outs (or Category A fit) provide the essential infrastructure – creating a space that is ready for tenant customisation. It’s serviceable and meets building regulations, but completely neutral. This CAT A space is what landlords deliver as the base level of finish.

The classification comes from British Council for Offices (BCO) specifications. While there’s no universal definition, most follow similar standards. That’s why requesting detailed specifications before signing your lease matters – what’s included in a CAT A varies significantly between buildings. In particular, in the post-Covid commercial marketplace typified by a “flight to quality”, we have seen an increase in fitting out to a more developed CAT A+ specification, with additional features installed to attract prospective tenants.

At Highgate Studios, we delivered a CAT A project across 12 units over 46 weeks. Working in a live, multi-tenant building meant careful coordination – upgrading mechanical services, installing new ventilation and heating systems, plus LED lighting throughout while existing office space remained operational.

Shell and Core vs CAT A Fit Outs vs CAT B Office Fit Outs

 Shell and core: The basic building structure – an empty shell with structural elements, external walls, and concrete and metal frame. Everything from HVAC systems to wall finishes needs installing at this shell and core stage. A true shell and core space requires the most work.

CAT A fit outs: Built upon shell and core, adding infrastructure like raised flooring, suspended ceilings, M&E services, and toilets. The workspace is ready for occupation but requires customisation to suit your operations. This CAT A and B distinction is crucial for budgeting.

CAT B fit outs: Your commercial fit-out transforming CAT A infrastructure into a fully functional environment with meeting rooms, furniture, kitchens, and branding. This is the process of bringing an empty space to life as a functional and personalised office.

What is a CAT B Fit Out?

CAT B fit outs (or Category B) transform basic infrastructure into your specific environment – whether commercial office fit-outs, healthcare facilities, educational settings, or specialist use. These different types of office fit outs serve varied operational requirements.

What’s Included in CAT B Office Fit Outs

The gap between CAT A and functioning workspace represents your CAT B scope:

• IT and telecoms cabling
• Reception area and office design elements
• Enhanced lighting and acoustics
• Signage and wayfinding

South Kilburn Medical Practice shows CAT B in healthcare – transforming a developer shell within a 17-storey mixed-use development into a 20,000 sq ft medical centre. The design and build included 6 consulting rooms, 2 counselling rooms, 2 treatment rooms, and 2 phlebotomy rooms. These specific needs required extensive stakeholder engagement, to deliver a fully NHS compliant space, fit-for-purpose to allow the incoming Medical Centre staff to deliver the highest possible standard of care. . Phased construction allowed the tenant to move in progressively, creating a functional office environment meeting NHS compliance.

CAT A and CAT B Office Fit Outs Comparison

Office Fit Out Costs 2026: Types of Office Fit Outs

Industry data for commercial office fit-outs and commercial office space 2026:

CAT A Costs: Typically £50-100 per sq ft, funded by landlords. Variables include building age, location, and level of finish.

CAT B Costs (by different types of fit outs):

• Basic specification: £40-60 per sq ft
• Mid-range specification: £60-80 per sq ft
• High specification: £80-120 per sq ft
• Premium bespoke: £140-250 per sq ft

Regional variations: London commercial office space averages around £175 per sq ft due to increased labour and material costs. Existing office refurbishment outside major cities falls closer to £70-100 per sq ft.

Furniture: Add £12-35 per sq ft.

Example: A 5,000 sq ft workspace with mid-range CAT B specification costs approximately £350,000-£475,000 total (£60-80 per sq ft plus £15-20 per sq ft furniture).

CAT A+ and Plug and Play: CAT A Space Options

Landlords increasingly offer enhanced specifications between standard CAT A space and full CAT B:

CAT A+ (Enhanced Category A Fit): Higher quality finishes, enhanced lighting, upgraded systems, increased power density, better acoustics.

Plug and play: Semi-fitted spaces where tenants can move in with minimal adjustments – furniture provided, partitioning exists. Tenant can move in quickly.

Both reduce your CAT B scope. Common in the City and West End where occupiers want immediate occupation.

We help clients evaluate whether enhanced specifications genuinely reduce scope or if they’re paying for unnecessary upgrades. The right answer depends on tenure length, operational requirements, and how much you need to customise the space to meet your workspace to suit preferences.

CAT A or CAT B: Which Office Fit Out Do You Need?

A CAT A space works for:

• Short tenures (2-3 years) where investment doesn’t pay back
• Organisations with minimal requirements
• Phased improvement budgets

A full CAT B office fit out is essential for:

• Tenures of 5+ years (investment payback justifies cost)
• Client-facing environments needing identity expression
• Specific needs (healthcare compliance, specialist equipment)
• Attracting talent in competitive markets

Healthcare facilities require extensive CAT B work to meet compliance standards. Educational environments need specialist teaching spaces and laboratories. Commercial office fit-outs vary based

Before Signing Your Lease: Office Fit Outs Checklist

✓ EPC rating and energy performance

✓ M&E drawings

✓ Works explicitly excluded from scope

Request your landlord’s full specification document. What’s “standard” varies significantly. At Highgate Studios, we upgraded services that technically fell outside our scope but required complete replacement to meet modern standards.

Guide to Office Fit Outs

CAT A delivery: 12-20 weeks depending on building size and any requirements to phase works around incumbent tenants. Heritage buildings extend timelines due to constraints and approvals.

CAT B office fit outs delivery:

• Small workspace (2,000-3,000 sq ft): 8-10 weeks
• Medium workspace (3,000-8,000 sq ft): 10-14 weeks
• Large workspace (8,000+ sq ft): 14-20 weeks

Factor in office design time (4-6 weeks) and furniture procurement (8-12 weeks). Starting design before completion accelerates occupation and office move.

Healthcare and educational projects typically require longer programmes due to compliance requirements and specialist equipment installation.

How We Navigate CAT A Fit Outs and CAT B Fit Outs

We start every fit-out project by understanding three things:

1. Tenure Length Longer tenures justify higher investment. We help calculate cost per year of occupation to determine what level of finish makes financial sense.

2. Operational Requirements We map your specific needs against what infrastructure and finishes are provided. Healthcare facilities like South Kilburn Medical Practice require extensive work to meet NHS compliance. Commercial office fit-outs may need less. Heritage buildings require specialist expertise balancing customisation with conservation.

3. Market Leverage In tenant-favourable markets, landlords may contribute to costs. We’ve worked with clients to secure enhanced specifications or contributions reducing upfront capital requirements.

2026 Office Fit Outs and Office Design Trends

Sustainability requirements: With EPC rating C mandatory from April 2025 and EPC B to be required by April 2030, refurbishment projects target higher environmental standards. Many projects now achieve EPC B through thermal upgradesand installation of more efficient lighting and HVAC systems.

Flexible specifications: Demand for adaptable spaces increased year-on-year, shifting how landlords approach specifications to accommodate diverse requirements.

Landlord-funded options: More landlords fund upfront costs across tenure terms, easing capital requirements for occupiers.

Working with Fado on CAT A Fit Outs and CAT B Fit Outs

We’ve delivered fit outs across London, spanning every specification variation and complexity – from heritage buildings in Mayfair to healthcare facilities in mixed-use developments, from fast-paced 8-week refurbishments to 46-week multi-tenant programmes.

Our projects span commercial, healthcare, education, and specialist sectors. Whether NHS-compliant medical centres, corporate environments, educational facilities, or heritage refurbishments, we bring sector-specific expertise across all types of office fit outs.

We work with clients from negotiation through to handover, clarifying what infrastructure is provided, what you’ll fund, and how to avoid specification surprises. Our in-house FF&E facility coordinates furniture procurement and installation, providing single-point accountability across design, construction, and furnishing.

If you’re planning CAT A fit outs or CAT B office fit outs, speak to our team: Visit fado.co.uk