CAT A vs CAT B Commercial Fit-Out: What London Landlords Need to Know

A plain-English guide to CAT A and CAT B commercial fit-out — what each covers, who typically pays, and how it relates to dilapidations.

If you own, manage or lease commercial space, you will hear the terms "CAT A" and "CAT B" used constantly — and often interchangeably, which causes confusion. They describe two different stages of commercial fit-out, with different scopes, different budgets and, usually, different parties paying for them. This guide explains the difference in plain English for London landlords and tenants.

What is a CAT A fit-out?

A CAT A (Category A) fit-out delivers a functional but blank commercial space, ready for a tenant to move in and add their own finishes. It is typically the landlord’s responsibility and usually includes raised floors and suspended ceilings, basic mechanical and electrical services, lighting, heating, ventilation and air conditioning, fire detection and finished common areas. The result is a clean, lettable shell — but not somewhere you could yet run a business day to day.

What is a CAT B fit-out?

A CAT B (Category B) fit-out turns that blank space into a finished, branded, operational workplace. It is usually the tenant’s responsibility and reflects how the specific occupier will actually work. CAT B typically covers partitioning and meeting rooms, kitchens and tea points, reception and breakout areas, flooring and decoration, furniture, branding, and the adaptation of the base M&E and lighting to suit the new layout.

Who pays for what?

• CAT A — typically funded by the landlord as part of providing a lettable space.
• CAT B — typically funded by the tenant, sometimes offset by a landlord contribution or rent-free period.
• The exact split is set by the lease and the heads of terms, so it pays to agree scope early.

Where dilapidations come in

At the end of a lease, dilapidations are the works (or financial settlement) required to return the space to its agreed condition — often back to a CAT A standard. Planning your fit-out and your exit together avoids surprises, because the way a CAT B is installed affects how easily and cheaply it can be stripped out later. A contractor experienced in both fit-out and dilapidations can help you plan for the whole lifecycle rather than just the move-in.

Planning a fit-out with minimal disruption

In live, occupied or multi-tenant buildings, timing matters as much as scope. Out-of-hours and phased working keeps neighbouring occupiers running while your space is transformed. RS Construction and Property Services Ltd delivers office refurbishment, CAT A and CAT B fit-out, dilapidations and 24/7 reactive maintenance for commercial property across East London and London. If you are planning a move or refurbishment, talk to our team early so scope, budget and programme line up from the start.