Cat A vs Cat B Fit-Out: What Each Stage Means for Commercial Tenants

If you are taking space in a commercial building in London, you will hear the terms Cat A and Cat B. They describe two stages of fitting out an interior, and understanding the difference helps you budget, plan your programme and negotiate your lease.

What Cat A covers

Cat A is the base fit-out that makes a space usable. It is usually provided by the landlord or developer, although this varies by building and lease. It typically includes:

• Raised access floors and suspended ceilings

• Basic mechanical and electrical services, including lighting and air handling

• Fire detection and life safety systems

• Basic finishes to walls, floors and ceilings

• Toilets and common areas

What Cat B covers

Cat B is the tenant's own fit-out, which turns the space into a working environment for your business. It normally covers:

• Partitioning, meeting rooms and reception areas

• Joinery, furniture and branded finishes

• Data, IT and audio-visual installations

• Adjustments to lighting and air conditioning to suit the layout

• Kitchenettes, breakout areas and wellbeing spaces

Why the split matters

• It affects your costs and how much you need to budget on top of rent

• It determines who is responsible for design, approvals and programme

• Landlord consent and a licence for alterations are often needed before Cat B works begin

• Lease terms may require the space to be reinstated when you leave

Programme and planning

Cat B works need to fit around your move-in date, so design, approvals and long lead-time items should be organised early. Working with a team that can handle design coordination and construction together makes it easier to protect the programme.

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