The simple explanation

CAT A is what the landlord delivers. It's a functional but bare shell everything is working, but nothing is personalised. You could occupy it, but it wouldn't feel like your office.

CAT B is what you add on top. It's the fit out that turns a blank canvas into your branded, operational workplace with your layout, your finishes, your furniture, and your identity.

Think of CAT A as a new house with plastered walls and a boiler, and CAT B as the decoration, furniture, and everything that makes it feel like home.

What's included in each?

CAT A Landlord Delivers
The shell
  • Raised access floors
  • Suspended grid ceiling with basic lighting
  • Perimeter trunking and basic power distribution
  • Heating, ventilation and air conditioning (HVAC)
  • Toilet cores and welfare facilities
  • Fire detection and suppression systems
  • Lifts and common areas
  • Basic finishes (painted walls, carpet tiles)
CAT B You Deliver
Your office
  • Partitioning glass, solid, demountable
  • Meeting rooms, private offices, breakout areas
  • Reception area and feature entrance
  • Kitchen, tea points, and café facilities
  • Flooring upgraded carpet, timber, tiles, concrete
  • Bespoke joinery and feature walls
  • Furniture and FF&E
  • AV, technology, and data infrastructure
  • Branding, signage, and wayfinding
  • Upgraded lighting and controls
Key point: CAT A is typically paid for by the landlord as part of the base rent deal. CAT B is paid for by the occupier though landlords will often contribute via a fit out allowance or rent-free period.

Is there a CAT A+?

Yes CAT A+ (also called "plug and play") is a growing trend in the London market, particularly for flexible and co-working spaces. It sits between CAT A and CAT B: the landlord delivers a space that is already fitted out to a generic office standard, so an occupier can move in immediately with minimal additional works.

CAT A+ typically includes open-plan desking, meeting rooms, a kitchen, and AV but without any occupier-specific branding or bespoke design. It suits businesses that need speed, flexibility, or don't want the capital expenditure of a full CAT B fit out.

Who pays for what?

The landlord's obligations

In a standard London office lease, the landlord is responsible for delivering the building to CAT A standard. This is confirmed in the lease agreement and is a condition of the building being ready for occupation. The quality of CAT A varies significantly between buildings and landlords a new-build in Canary Wharf will have a much higher CAT A specification than a 1990s office in the suburbs.

The occupier's obligations

CAT B is the occupier's responsibility and cost. However, in the current London market, it is standard practice for occupiers to negotiate a landlord fit out contribution typically £15–40 per sq ft as part of the lease terms. This effectively reduces your out-of-pocket CAT B cost.

Alternatively, landlords may offer an extended rent-free period 6, 9, or 12 months during which you can complete the fit out and begin trading before rental payments begin.

How long does each take?

CAT A is delivered by the landlord and is typically complete before you sign the lease. If you're taking space in a new development, CAT A may be completed as part of the base build programme.

CAT B, once you have a design and building contract in place, typically takes:

Plan your CAT B programme before you sign the lease and factor it into your rent-free negotiation. If you need 16 weeks on site, you need at least 20–22 weeks of rent-free to avoid paying rent before you can occupy.

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Frequently asked questions

Can I skip CAT A and go straight to CAT B?

If you are taking a second-hand space that was previously fitted out, you may be taking it in "CAT B" condition i.e. with an existing layout, partitions, and finishes. In this case you would either refurbish the existing fit out or strip it back to CAT A before completing your own CAT B. A Setro consultant can advise on the most cost-effective approach.

What if the CAT A is poor quality?

CAT A quality varies enormously. Before committing to a space, it is worth commissioning a technical survey to assess the condition of the M&E, the ceiling grid, the raised floor, and the toilet cores. Upgrading poor-quality CAT A as part of your fit out adds significant cost and should be reflected in your landlord negotiation.

Does CAT B include furniture?

Not always. Many fit out contracts include the construction works (partitions, flooring, M&E, joinery) but exclude furniture as a separate procurement package. At Setro we offer FF&E procurement as part of our service, ensuring your furniture specification is coordinated with the design intent from day one.