Cat B fit-out costs are among the most searched — and most misunderstood — figures in commercial property. Benchmarks vary widely depending on specification, location, and what is included in the contractor's scope. This guide sets out 2026 per m² figures from Cushman & Wakefield, Turner & Townsend, and BCIS, explains what drives the variation, and gives you a practical framework for budgeting your next office fit-out in London or Hertfordshire.
Cat A vs Cat B: Understanding the Distinction
The Cat A / Cat B distinction is a UK commercial property convention, not a formal standard, but it is widely understood by landlords, tenants, and contractors. A Cat A fit-out delivers a functional but bare space — raised access floors, suspended ceilings, basic HVAC, power distribution, and fire detection — and is typically the landlord's responsibility. A Cat B fit-out is the tenant's responsibility and turns that blank canvas into a fully operational, branded workplace.
The boundary between Cat A and Cat B is not always clean. Some landlords now offer "Cat A+" or "plug-and-play" spaces that include a proportion of Cat B elements — basic partitioning, a fitted kitchen, and some furniture — to reduce the tenant's fit-out cost and time. When comparing quotes, it is essential to establish exactly which elements are included in each scope.
For a full overview of the commercial fit-out process from Cat A shell to operational workplace, see our commercial fit-out process guide.
2026 Cat B Fit-Out Cost Benchmarks
The table below sets out 2026 per m² benchmarks for Cat B office fit-outs across three specification levels and two geographies, drawn from the Cushman & Wakefield 2026 Fit-Out Cost Guide, the Turner & Townsend 2026 UK Cost Report, and BCIS Office Cost Data Q1 2026.
| Specification | Central London (£/m²) | Herts / North London (£/m²) | Typical Use Case |
|---|---|---|---|
| Standard Cat B | £600–£900 | £500–£750 | Professional services, back-office, call centre |
| Mid-Range Cat B | £750–£1,100 | £620–£900 | Tech, media, modern SME office with good joinery |
| High-Spec Cat B | £1,200–£1,800 | £950–£1,400 | HQ, flagship office, premium materials and AV |
| Cat A (for reference) | £380–£550 | £300–£450 | Shell and core services, landlord-delivered |
Sources: Cushman & Wakefield Fit-Out Cost Guide 2026 (London £148–£359/sqft for Cat B); Turner & Townsend UK Cost Report 2026; BCIS Office Cost Data Q1 2026. Hertfordshire and North London figures are 10–20% below central London benchmarks based on TCM internal data 2026 (n=23 commercial projects). All figures exclude furniture, VAT, and professional fees unless stated.
Cat B Cost Breakdown by Element
Understanding how Cat B costs are distributed across elements helps you identify where specification decisions have the greatest impact on budget. The figures below are based on a mid-range Cat B fit-out at £800/m² in central London.
| Element | % of Total Cost | Cost at £800/m² (per m²) | Key Cost Drivers |
|---|---|---|---|
| Joinery & Furniture | 20–25% | £160–£200 | Reception desk, breakout, storage, bespoke millwork |
| Partitioning & Glazing | 15–20% | £120–£160 | Glazed partitions vs solid; acoustic performance |
| M&E Upgrades | 15–20% | £120–£160 | HVAC distribution, power, lighting design |
| IT & AV Infrastructure | 10–15% | £80–£120 | Structured cabling, AV, server room fit-out |
| Flooring & Decoration | 8–12% | £64–£96 | Carpet, LVT, feature walls, paint |
| Ceilings & Raised Floors | 5–10% | £40–£80 | Suspended ceiling tiles, access floor upgrades |
| Kitchen & Welfare | 5–8% | £40–£64 | Fitted kitchen, WC upgrades, shower facilities |
| Prelims, Design & PM | 10–15% | £80–£120 | Site management, design fees, project management |
Source: TCM internal cost analysis 2026 (n=23 commercial fit-out projects); Cushman & Wakefield 2026 Fit-Out Cost Guide. Percentages are indicative and will vary with specification and project size.
What Drives Cat B Cost Variation?
The single largest driver of Cat B cost variation is joinery specification. A reception desk fabricated from solid oak with integrated LED lighting and bespoke metalwork can cost £15,000–£40,000; a standard laminate desk costs £3,000–£6,000. Similarly, glazed partitioning with acoustic performance to Rw 45 dB costs 40–60% more than standard single-glazed demountable partitions. Specification decisions in these two elements alone can move the total project cost by 20–30%.
M&E upgrades are the second major variable. If the Cat A shell includes adequate HVAC capacity and power distribution, Cat B M&E costs are limited to final distribution, lighting design, and controls. If the Cat A is under-serviced — a common issue in older buildings — the tenant may need to fund additional plant, which can add £80–£150/m² to the Cat B budget. For a detailed breakdown of M&E costs in commercial fit-outs, see our article on M&E for commercial fit-outs.
Project size also affects unit costs significantly. A 200 m² fit-out will cost 20–30% more per m² than a 2,000 m² fit-out for the same specification, because fixed preliminaries and mobilisation costs are spread across fewer square metres. TCM's minimum project size for a Cat B office fit-out is 150 m².
Cat B Fit-Out Costs in Hertfordshire and North London
Hertfordshire's commercial property market — centred on Watford, St Albans, Hemel Hempstead, and Borehamwood — offers significantly lower fit-out costs than central London, while maintaining access to the same quality of contractor and supply chain. TCM's 2026 project data shows Cat B fit-out costs in Hertfordshire running 10–20% below the central London benchmark, reflecting lower labour costs and reduced preliminaries (less complex logistics, no congestion charge, lower skip and waste disposal costs).
North London — including Barnet, Finchley, Hendon, and Edgware — sits between central London and Hertfordshire in cost terms, typically 5–15% below the central London benchmark. For businesses relocating from central London to North London or Hertfordshire, the fit-out cost saving is often significant enough to offset a proportion of the relocation costs.
How to Budget for a Cat B Fit-Out
The most common budgeting mistake is using a single per m² benchmark without adjusting for specification, project size, or geography. A more reliable approach is to build the budget from the element breakdown above, applying the specification level appropriate to each element independently. This allows you to identify where to invest (joinery and AV, which are highly visible to staff and visitors) and where to value-engineer (raised floors and suspended ceilings, which are largely invisible once installed).
TCM provides a detailed elemental cost plan at RIBA Stage 2 (Concept Design) as part of the pre-construction service, allowing clients to make informed specification decisions before the project is committed to tender. For a full overview of the commercial fit-out process, see our commercial fit-out cost guide.
Cat B Fit-Out — Free Cost Plan
TCM provides a free elemental cost plan for Cat B office fit-outs in Hertfordshire and North London. We cover offices from 150 m² to 5,000 m² and manage the full process from design to handover.