A Cat A fit out transforms a bare shell and core space into a clean, serviced environment that is ready for occupation or further tenant customisation. Whether you are a landlord preparing a floor plate for the letting market, a developer handing over a refurbished building, or a tenant who has taken on raw space, the Cat A phase is the essential foundation that makes everything else possible. At Office Refit, we deliver Cat A fit out projects across London, working with commercial landlords, property managers, and occupiers to create spaces that meet current building regulations, comply with accessibility standards, and present well to prospective tenants.

What Is a Cat A Fit Out?

Cat A fit out refers to the base build that takes a shell and core space to a “ready for occupation” standard. It sits between the structural shell (the concrete frame, external envelope, and core services provided by the developer) and the personalised interior that a tenant would later install as part of a Cat B fit out. The purpose of Cat A is to provide a neutral, functional baseline: the floors are raised and levelled, the ceilings are suspended and tiled, the mechanical and electrical services are distributed to floor level, and the common areas are finished to a professional standard.

In practical terms, a completed Cat A fit out means that anyone walking onto the floor plate will find a clean, open-plan space with level flooring, consistent ceiling heights, adequate lighting, comfortable temperatures, and functioning life-safety systems. The space will not yet have partitioned offices, branded finishes, or bespoke furniture layouts; those elements belong to the Cat B phase. However, the Cat A standard ensures that the building is fully compliant, safe, and ready for a tenant to begin their own interior design works without delay.

Typical elements delivered during a Cat A fit out include raised access floors, suspended ceiling grids with mineral fibre tiles, basic mechanical ventilation or fan coil units, primary electrical distribution to floor boxes, emergency lighting, fire detection and alarm systems, sprinkler installations, toilet and washroom facilities within the core, and finished lift lobbies. The exact specification will depend on the building’s age, the landlord’s aspirations, and the target letting market, but the principle remains the same: provide a solid, well-serviced base that minimises the time and cost a tenant needs to invest before moving in.

Cat A vs Cat B: What Is the Difference?

The distinction between Cat A and Cat B is one of the most common questions in commercial fit out, and getting the boundary right is important for budgeting, programming, and lease negotiations. Cat A is the landlord standard base build. It delivers the generic infrastructure that any tenant would need: raised floors, suspended ceilings, distributed mechanical and electrical services, and compliant life-safety systems. It is deliberately neutral, designed to appeal to the widest possible range of occupiers.

Cat B, by contrast, is the tenant-specific personalisation layer. This is where the space gains its identity: partitioned meeting rooms, open-plan desk layouts, reception areas, branded finishes, bespoke joinery, AV installations, and specialist lighting. Cat B works sit on top of the Cat A foundation, using the services and structure already in place. A well-executed Cat A fit out makes the subsequent Cat B phase faster, cheaper, and less disruptive because the heavy infrastructure is already done.

If you are planning the next phase after your Cat A is complete, visit our Cat B Fit Out London page to learn more about tenant-specific interior works and how the two phases connect.

What Does a Cat A Fit Out Include?

Every Cat A specification is different, but the following elements form the core scope of works on the majority of London commercial projects:

Raised access flooring to provide a level surface and concealed routes for cabling and small-bore services
Suspended ceiling grid with mineral fibre tiles to conceal services above and deliver a clean, consistent ceiling plane
Perimeter trunking and dado systems for power, data, and small power distribution around the floor plate
Primary mechanical and electrical distribution, including fan coil units or VAV boxes, main lighting circuits, and sub-distribution boards
Basic LED lighting to general office areas, providing adequate lux levels for open-plan working
Fire alarm and detection systems, including smoke detectors, sounders, call points, and interface with the building’s main fire panel
Sprinkler systems with heads on a standard grid layout, ready for adjustment during the Cat B phase if partitions are introduced
Toilet and kitchen shell, including sanitaryware, vanity units, tiling, and mechanical extract within the core areas
DDA compliance, ensuring accessible WC facilities, appropriate door widths, level thresholds, and tactile signage where required

The specification should be agreed early in the project and documented clearly so that the boundary between Cat A and Cat B is understood by all parties, particularly where the landlord is funding Cat A and the tenant is responsible for Cat B.

Cat A Fit Out Process

Delivering a Cat A fit out follows a structured sequence that balances speed with quality. Landlords and developers often work to tight letting deadlines, so the programme needs to be realistic and well-managed from day one. Below is the typical process we follow on our London Cat A projects.

Survey and assessment. We begin with a detailed site survey to understand the existing shell and core condition, confirm structural layouts, identify any remedial works, and verify the status of incoming services. This information feeds directly into the design phase.

Design and specification. Working alongside M&E consultants and the project team, we develop the Cat A specification, produce layout drawings, and confirm the finish standards. Where a landlord has an established Cat A spec, we review it for buildability and value engineer where appropriate.

Procurement. Long-lead items such as fan coil units, ceiling tiles, and raised floor pedestals are ordered early to protect the programme. We work with trusted supply chain partners to secure competitive pricing and reliable delivery.

Strip out (if required). On refurbishment projects, the existing fit out must be removed before Cat A works can begin. This may include demolition of partitions, removal of old ceilings and floors, and safe disposal of redundant services.

M&E first fix. Mechanical and electrical contractors install primary distribution, ductwork, pipework, containment, and fire protection. This is the most intensive phase and must be carefully coordinated to avoid clashes.

Ceilings and floors. Once the overhead services are in place and tested for leaks, the suspended ceiling grid is installed, followed by the raised access floor. These two elements define the finished floor-to-ceiling height and must be precisely levelled.

M&E second fix. Lighting, power, data outlets, grilles, diffusers, and terminal devices are fitted through the ceiling and floor systems. Fire alarm devices, sprinkler heads, and emergency lighting are also completed at this stage.

Testing and commissioning. All mechanical, electrical, and life-safety systems are tested, balanced, and commissioned. Documentation is compiled for handover, including O&M manuals, as-built drawings, and compliance certificates.

Handover. The completed floor plate is handed over to the landlord or tenant, ready for marketing, Cat B works, or occupation. A snagging inspection identifies any minor defects for rectification during the defects liability period.

Cat A Fit Out Costs in London

Cat A fit out costs in London typically range from £40 to £70 per square foot for a standard commercial office specification. This range covers the core elements outlined above: raised floors, suspended ceilings, basic M&E distribution, lighting, fire detection, and common area finishes. The exact figure will depend on several factors, and it is worth understanding what drives costs up or down before setting your budget.

Central London locations carry a premium. Projects in the City of London, the West End, and Southbank corridors tend to sit at the upper end of the range due to higher labour costs, restricted working hours, complex logistics, and the quality expectations of the letting market. A Cat A fit out in a modern tower near Liverpool Street will typically cost more per square foot than a similar scope in an outer London business park.

Other factors that influence cost include the condition of the existing shell (older buildings may need more remedial work), the floor-to-ceiling height (taller voids require more material), the quality of specified finishes (premium ceiling tiles and high-grade raised floor panels add cost), and the programme (accelerated timelines often attract premium preliminaries). We provide fixed-price quotations after a thorough site survey and specification review, so you know exactly what the investment will be before work begins.

Areas We Cover

We carry out Cat A fit out projects across central London and the surrounding commercial districts. Our teams are experienced in working within occupied buildings, managing out-of-hours access, and coordinating with building management teams in some of the capital’s busiest office locations. Below are some of the areas where we regularly deliver projects:

If your building is outside these areas, get in touch. We work across Greater London and the Home Counties for larger Cat A programmes.

Get Your Cat A Quote

Whether you are preparing a single floor for the letting market or delivering a multi-storey Cat A programme across an entire building, our team can help. We offer fixed-price quotations, realistic programmes, and a straightforward approach that keeps landlords and developers informed at every stage.

Contact us today to discuss your Cat A fit out requirements. Send us your floor plans and specification, and we will come back to you with a detailed proposal and programme within five working days.

Request a Cat A Fit Out Quote