Category B Fit Out Guide: Everything You Need to Know About Cat B Work

You’ve signed the lease, walked the floor, and now you’re staring at a clean but empty office. Carpet, ceiling tiles, base lighting, air conditioning humming overhead. It looks finished. It isn’t. That space is a Cat A shell, and the work that turns it into a place your team can actually use is a Category B fit-out.

This guide walks through what Cat B work covers, how the process works, what drives costs, and where projects go wrong. The aim is to help you make sharp decisions before you commit budget and time.

What Is a Category B Fit Out?

A Category B (Cat B) fit-out is the tenant’s project that transforms a base-finished office into a working space tailored to how your business operates. It’s the layer where meeting rooms appear, partitions go up, branding hits the walls, and the layout starts matching your team’s real workflow.

Here’s the sequence. A landlord hands over a shell-and-core (structure only), then usually finishes it to Cat A (a generic but functional space with raised floors, suspended ceilings, base lighting, and HVAC). Cat B picks up from there and runs to the point where people can move in and work.

So Cat A makes the building lettable. Cat B makes it workable. That line decides who pays for what, who runs the job, and what state you must return the space in when the lease ends.

Set one thing straight early: Cat B is not a fixed package. Two tenants in the same building can run completely different scopes depending on headcount, culture, compliance needs, and budget. Treat any “standard Cat B” quote with suspicion until you’ve defined your own brief.

Cat A vs Cat A+ vs Cat B: What You’re Actually Getting

Most confusion in early lease talks comes from these labels being used loosely. No legal rulebook governs them, so what’s “included” shifts by landlord and building. The working definitions still hold up well.

A word on Cat A+, because it trips people up. Some landlords now deliver a partial fit-out (desks, a couple of meeting rooms, a tea point) to fill space faster. If your building offers this, raise it early in budget talks. It can shrink your Cat B scope, but it can also cap how much you customize.

And kill the most common myth now: tenants often assume the landlord’s fit-out sits inside the rent. It usually doesn’t. Cat B is almost always a tenant cost, and it’s often the biggest single spend of the move.

What a Cat B Fit Out Includes (and What It Doesn’t)

Knowing the boundary between Cat B and everything else saves you from surprises when the final invoice lands. Here’s how the scope typically splits.

Inside a standard Cat B scope:

• Interior construction — partition walls, glazed partitions, doors, feature ceilings, and floor finishes. If you’re carving an open floor plan into offices, meeting rooms, and quiet zones, consider demountable wall systems early. They let you reconfigure later without ripping out drywall, which matters if your headcount is moving.
• Mechanical and electrical (M&E) — adapting the base HVAC to your new layout, adding power and lighting circuits, small power, and tying into the fire alarm.
• Data and connectivity — structured cabling, containment, and comms room fit-out. The IT hardware itself is usually separate.
• Finishes — paint, joinery, wall coverings, tiling, and acoustic treatments.
• Specialist installs — meeting room AV, access control, security, and signage.

Usually outside Cat B, quoted separately:

• Loose furniture and workstations
• IT hardware, servers, and telecoms equipment
• Artwork, planting, and some branding elements
• Move management and decanting costs

The line moves, though. Plenty of tenants fold furniture and even some IT into a single Cat B budget so there’s one team and one point of accountability. If you’re specifying height-adjustable desks or bespoke workstations, decide up front whether they live in the fit-out contract or a separate furniture order. That call affects lead times and who bears the blame if something arrives late.

Acoustic planning earns a special mention. Open-plan floors look great in a render and sound terrible in real life. Designing focus zones, phone booths, and meeting pods into the Cat B layout from the start is far cheaper and cleaner than bolting them on after the complaints begin.

How the Category B Fit Out Process Works

Most standard office fit-outs run 8 to 16 weeks from locked design to handover. Here’s what happens at each stage.

1. Briefing and space planning. You translate business needs into a layout. How many people today, and in two years? How many meeting rooms do you actually use versus book “just in case”? What’s your split between focus work and collaboration? Get this wrong, and every later stage inherits the error.

2. Design development. Mood boards, adjacency diagrams (which teams sit near which), and early compliance checks for fire safety, accessibility, and building regulations. This is when your designer flags base-building constraints that shape what’s possible.

3. Budgeting and procurement. A detailed scope and bill of quantities become a fixed price. Long-lead items — glazing, bespoke joinery, AV, specialist furniture — get ordered now, not later.

4. Pre-construction and permits. Building control approval, the landlord’s license to alter, and any party wall agreements. Underestimate this stage and your program slips before a wall goes up.

5. Construction and fit out. Strip-out where needed, then first fix (M&E, partitions, ceilings), then finishes and second fix. This is the visible part, and usually the shortest relative to the planning behind it.

6. Snagging and handover. Every defect gets logged and fixed, systems are tested and commissioned, and you receive as-built drawings, warranties, and maintenance schedules. Don’t sign off until the snag list is genuinely closed, not just promised.

Here’s a realistic timeline by office size:

What blows these estimates? Slow landlord consents, planning approvals, material lead times, the condition of the existing slab, and indecision on the tenant side. That last one is the quiet killer. A team that can’t approve a finish or sign off a layout on time will stretch any program.

Before you sign anything, get a clear program with named milestones. A vague “about three months” is a red flag.

Who Pays for a Cat B Fit Out, and What Drives the Cost

In most commercial leases, the landlord delivers Cat A and the tenant funds Cat B. Some landlords offer a contribution or rent-free period to offset it, so always ask during lease negotiations.

The final price per square foot swings on a handful of variables:

• Building condition and existing services — a well-specified Cat A shell with spare HVAC capacity and generous risers costs less to build on than a tired, tight one.
• Level of specification — a clean, functional office and a heavily branded headquarters are entirely different budgets.
• Furniture, IT, and AV integration — the more you bundle in, the higher the number.
• Location and contractor rates — regional labor and material costs vary widely.
• Planning and building control fees.

Before you set a budget, read the landlord’s Cat A specification carefully. Capped floor loads, limited base HVAC capacity, and small riser allowances quietly restrict what you can do and can force expensive workarounds. A good site survey catches this early.

Choosing a Delivery Model

You’ve got three main routes:

• Design and build — one contractor owns design and construction. Single point of responsibility, faster, and the default for most standard fit-outs.
• Traditional — separate design team and contractor. More design control, but you carry the coordination risk.
• In construction management, you engage multiple trade contractors directly. Flexible for large or complex jobs, but management-heavy.

For a typical Cat B office design and build usually wins on speed and accountability. When something goes wrong, there’s no finger-pointing between designer and builder, because they’re the same team.

Common Mistakes to Avoid

These pitfalls turn up on Cat B project after Cat B project. Here’s how to sidestep each one.

Starting design before the budget and constraints are clear. It’s tempting to jump into layouts and mood boards. Resist it. Lock your budget and run a proper survey first, or you’ll design a space you can’t afford or the building can’t support.

Skipping a thorough site survey before pricing. No survey means assumptions, and assumptions become change orders once construction reveals what’s behind the walls and under the floor. The survey costs a little now and saves a lot later.

Underestimating landlord approvals. The license to alter can take weeks, and construction can’t legally start without it. Build it into your program on day one and chase it early.

Ordering furniture and long-lead items too late. Bespoke furniture, glazing, and AV can carry lead times of many weeks. Order during procurement, not when the walls are up. Late furniture is one of the most common reasons a “finished” office can’t actually be used on day one.

Ignoring acoustics and privacy in open plan. Open-plan, without a focus strategy, breeds noise, distraction, and unhappy staff. Design in quiet rooms, booths, and treated zones from the start. Retrofitting privacy is always messier and pricier.

Chasing the lowest quote. The cheapest bid often hides vague scope lines, thin contingency, or a plan to claw margin back through change orders. Compare quotes on scope and track record, not the headline figure.

How to Choose a Cat B Fit Out Contractor

The right partner is the difference between a smooth handover and a stressful one. Here’s what to check before you shortlist.

Credentials to verify:

• Relevant experience with offices in a similar building type or sector
• Current accreditations (ISO 9001, CHAS, or local equivalents)
• Financial stability and proper insurance
• A track record with projects of your size and complexity
• Experience with your base building’s M&E systems where possible

Look past the headline price. Ask for case studies, then follow up references from tenants in comparable buildings. Find out how much they deliver in-house versus subcontract, and check their health and safety record and site management.

Five questions to ask before you sign:

1. Who is my single point of contact throughout the project?
2. What’s included in the fixed price, and what’s in provisional sums?
3. How are variations priced and approved once work starts?
4. What’s the defect liability period, and how is aftercare handled?
5. Can I visit a live site for a walkthrough?

That last question reveals more than any brochure. A tidy, well-run site tells you how your project will feel far better than a polished sales deck.

Frequently Asked Questions

How long does a Cat B fit out take?

Most standard office fit-outs run 8 to 16 weeks from locked design to handover. Small offices under 5,000 sq ft can be completed in 4 to 8 weeks, while a large headquarters over 20,000 sq ft often takes 12 to 20+ weeks. Landlord consents, permits, and long-lead materials are the usual causes of delay.

How much does a Cat B fit-out cost?

Cost per square foot varies widely by building condition, specification level, location, and the extent to which you fold in furniture, IT, and AV. A clean, functional office and a high-spec branded headquarters sit at very different price points. Get at least three quotes on a like-for-like scope before setting your budget.

Who pays for a Cat B fit-out, the landlord or the tenant?

In most commercial leases, the tenant funds Cat B, while the landlord delivers the Cat A base. Some landlords offer a cash contribution or a rent-free period to offset the cost, so raise it during lease negotiations.

Is furniture included in a Cat B fit-out?

Not automatically. Loose furniture, workstations, and IT hardware are usually quoted separately from the core Cat B works. Many tenants still bundle them into one budget for a single point of accountability. Decide this early, since furniture lead times can stretch for weeks.

How long does landlord approval take?

The license to alter can take several weeks, and construction can’t legally start without it. Submit your proposals early and chase them, because this approval is one of the most common causes of program slippage.

What are dilapidations, and do they affect Cat B?

Dilapidations are your obligation to return the space to an agreed condition at the end of the lease, often back to Cat A. Check this clause before you design anything, since heavy customization can mean a large reinstatement bill later.

The Bottom Line

A Cat B fit-out is your project, not the landlord’s, and it lives or dies on three things: a clear brief, a realistic budget, and a capable delivery team. Start with a detailed brief and a proper base-building survey before you commit to a design. Insist on a fixed-price contract with a transparent schedule of works, and hold a 5–10% contingency for the scope changes that always surface.

Before you go further, do three things: check your lease for reinstatement obligations, get at least three comparable quotes for a like-for-like scope, and confirm who owns the fit-out at lease end. Sort those now, and the rest of the project runs a lot more smoothly.