CAT A vs CAT B vs CAT A+: What London Office Landlords and Tenants Actually Need

The short version

CAT A is the landlord's base-build finish — raised floors, suspended ceilings, perimeter heating/cooling, and VRF/fan-coil units, with emergency lighting and a basic small-power distribution. It's "ready to fit out". Nobody can actually work in a CAT A space — it has no meeting rooms, no kitchen, no partitioning and no branding.

CAT A+ (sometimes written "CAT A plus") is CAT A with occupier-ready additions: meeting rooms, a small kitchen or tea point, basic furniture and some branding. It emerged in the 2020s as a way for landlords to let space faster, especially to occupiers under 5,000 sqft who don't want a full fit-out programme.

CAT B is the full tenant fit-out — everything the occupying business actually needs: partitioning, branded reception, full meeting-room suite, kitchens, collaboration zones, AV containment, bespoke finishes, decorative lighting, and all tenant-specific M&E alterations.

What's in CAT A (the landlord's obligation)

At heads of terms, a London commercial lease typically requires the landlord to deliver space to CAT A standard. That means:

• Raised access flooring (typically 150mm void for cable containment)
• Suspended ceiling with grid and standard tile (600×600 mineral fibre)
• Perimeter heating and cooling (VRF, fan coil units, or active chilled beams)
• Emergency and basic general lighting to CIBSE levels
• Small-power distribution to perimeter
• Commissioned mechanical ventilation meeting Part F
• Fire alarm, sprinkler and emergency systems to the demise
• WC facilities to BS 6465 provision calculations
• Typical CAT A cost: £60–£95 per sqft

What's in CAT A+ (the in-between)

CAT A+ extends the base build so the occupier can move in with minimal further work. Landlord agents push this hard on sub-5,000 sqft floors where a CAT B fit-out would add 10–16 weeks to the let.

• Meeting rooms (typically 2–6 rooms) with demountable partitions and doors
• Small tea point or kitchenette with sink, fridge, microwave
• Carpet (rather than just bare access floor)
• Paint (rather than just primer)
• Some loose furniture — desks, chairs, meeting-room tables
• Typical CAT A+ cost: £95–£140 per sqft

CAT A+ is not a statutory standard. It's a market convention. What's included varies by landlord — always check the specification drawings, not just the abbreviation.

What's in CAT B (the tenant's full fit-out)

CAT B is what most occupiers mean when they say "fit-out". It's everything bespoke to their business:

• Bespoke partitioning — full-height acoustic, glazed, or demountable
• Branded reception with feature walls and joinery
• Full meeting-room suite (boardroom, mid-size, pods, breakout)
• Full kitchens, tea points, collaboration zones
• AV containment for video wall, conferencing, presentation
• Bespoke lighting design — architectural, decorative, feature
• Custom flooring (LVT, engineered timber, bespoke carpet)
• Acoustic treatment — rafts, baffles, feature walls
• Typical CAT B cost: £120–£380+ per sqft depending on quality tier

Who pays for what

The standard structure on a new London commercial lease:

1. Landlord pays for CAT A

   Base-build finish to let-ready standard. Usually completed before heads of terms are signed.

2. Landlord may pay for CAT A+

   Where it's been added as a letting strategy. Sometimes offered as a rent-free period equivalent — "we'll CAT A+ the space for you".

3. Tenant pays for CAT B

   Usually with a landlord contribution (rent-free period, capital contribution, or both). Typical contribution: 3–12 months rent-free equivalent.

4. Tenant pays for dilapidations at lease end

   Tenant must reinstate CAT B works back to the landlord's CAT A specification at lease exit. Dilapidations cost: typically £15–£55 per sqft depending on scope.

Where the boundaries blur

The three levels aren't legally defined. In practice:

• Is a kitchenette part of CAT A+ or CAT B? Depends on the building. Always review the specification drawings.
• Is lighting scheme replacement CAT A+ or CAT B? If the CAT A lighting is kept, it's CAT B alterations. If the landlord upgrades the lighting before letting, it's CAT A+.
• What about M&E alterations? Landlord CAT A includes commissioned M&E. Any tenant-driven alteration (moving fan coils, adding sensors, reconfiguring small power) is CAT B.
• Partitioning at CAT A+? Usually only demountable systems so the next tenant can reconfigure without major works. Full-height acoustic and glazed partitioning is CAT B.

Programme durations

Typical programmes for a 10,000 sqft office in London:

• CAT A: 8–12 weeks from vacant demise to let-ready
• CAT A+: 10–14 weeks from vacant demise to occupier-ready
• CAT B: 10–16 weeks from licence-to-alter to practical completion
• Full CAT A then CAT B sequentially: 20–28 weeks

The common mistake at heads of terms

Occupiers routinely agree a landlord contribution at heads of terms without having a real CAT B costing. Three months later the actual CAT B quote comes in 40% above the contribution, and the lease is already signed. Best practice:

• Commission a fit-out cost plan before heads of terms are signed
• Visit the actual space with your contractor and architect before committing
• Request CAT A specification drawings at HoT stage, not at completion
• Factor dilapidations reinstatement into the 10-year total cost of occupation

What we do

We deliver CAT A, CAT A+ and CAT B fit-out across London — single project manager, fixed-price contracts, full compliance ownership. Survey and fixed quote within two weeks of instruction.

For a full breakdown of service scope, pricing bands and compliance, see the Office Fit-Out hub or the area-specific pages for City of London, Canary Wharf, Westminster & Victoria or Holborn.

FAQs