What does an office fit-out actually involve?

If the end of your lease is still two or three years away, “fit-out” probably sounds like a single job that happens near the end, somewhere after the building’s chosen. It isn’t.

A fit-out is a string of decisions that runs alongside your property search from the start, and it shapes more of that search than you might expect.

From the very start of the process when you’re shortlisting buildings, you’ll need to consider your headcount, whether your hybrid model will work on your chosen floorplate, and if the building can support your technology, culture and growth; all factors relevant to your fit-out.

Your fit-out journey: Interaction’s guide

This guide walks through what an office fit-out actually involves: what the terms mean, who’s on the team, when the big calls get made, what you’ll be asked to bring to the table, and where projects usually lose time.

Follow this guide, and your fit-out will be a smooth part of your wider journey; not a mad panic at the end of securing a lease.

By the end of this guide you’ll know:

• What Cat A, Cat B and Cat A+ actually mean
• Who needs to be involved, and when
• How early to start planning
• Where fit-out projects usually lose time
• What to prepare before speaking to agents, landlords or fit-out partners

First things first: what does fit-out actually mean?

A fit-out takes a base building, like a concrete shell, or a landlord’s basic finish, and turns it into a move-in ready space your team can work from on day one.

The important bit to understand here is where the responsibility sits for each of these elements. Cat A is usually the landlord’s baseline. Cat B is usually at your cost, but designed and built to your customised brief, on your timeline.

Useful to note: There is a third option: Cat A+. Sitting somewhere in the middle, Cat A+ is a fitted, furnished, move-in-ready space delivered by the landlord, but not personalised to you. It can be handy if you want speed or less upfront decision making, but not if you want a custom build.  

If you want the fuller picture, including where Cat A+ fits in, we’ve written up the difference between Cat A and Cat B office fit-out in more detail here.

So, who’s actually on the team?

A fit-out is a joint effort between your people and a small set of specialists. Knowing who does what early on saves you from duplicated effort, or worse: gaps nobody notices until they matter.

Most occupiers do better with a small group, rather than a large committee. You know what they say about too many cooks.

On your side, you’ll usually have:

• A project sponsor: usually a senior leader who owns the business case and clears roadblocks.
• An internal project lead: the day-to-day contact, coordinating HR, IT, finance and department heads.
• A HR or people lead: brings the culture and change management view.
• An IT or operations lead: owns technology, data, AV and any operational constraints.
• A finance representative: keeps budget, phasing and approvals aligned with your internal process.

Agreeing who has final sign-off on design, budget and programme (ideally before the project starts) is one of the more effective ways to keep things moving.

On the outside, the main players are:

• A design and build partner: brings workplace strategy, design, cost planning, construction and move-in support together under one accountable team. The alternative is knitting together a design firm, a contractor and a project manager yourself. We may be biased, but this is a much more time-consuming process with a larger margin for error. More on that below.
• A commercial agent: finds and negotiates the building, often using test-fit layouts and cost plans from your fit-out partner as evidence in that negotiation.
• The landlord and managing agent: control the base-build information and building rules, and their consent is required for most works.
• Specialist consultants where needed: a workplace strategist, cost consultant, building surveyor, acoustic or AV specialist, sustainability advisor, and legal advice on lease terms. Most occupiers prefer one partner as the main point of contact, who then manages the rest on their behalf. It’s fewer conversations, and fewer places for something to fall through a gap.

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A note on traditional fit-out vs design & build:

The choice between traditional and design and build ultimately comes down to how much time, cost and responsibility you’re willing to take on.

While a traditional route gives you more direct control over the design, it can also mean longer programmes, more coordination and greater potential for costly surprises when design meets construction.

Design and build tackles these challenges from day one, with designers and delivery teams working together to keep ambitious ideas grounded in practical budgets and timelines. The result? Fewer delays, clearer accountability and a smoother journey from first sketch to move-in day.

If you’re weighing up which route is right for you, we’ve set out why occupiers use a design and build firm for their next fit-out.

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The fit-out process, stage by stage

In more detail:

Strategy and options – roughly 18 to 24 months out.
This stage is about direction, not detail: clarifying growth plans, your hybrid working model, budget, preferred locations, and deciding whether to stay and refurbish or relocate.

It’s also the point to start early conversations with a fit-out partner for feasibility, rough costs and programme advice, alongside your commercial agent (before you’ve settled on a building).

Shortlisting buildings and test fits – roughly 12 to 18 months out.
Once you have a shortlist, test-fit space plans overlay your headcount and ways of working onto the real floorplates, so you know what’s actually achievable before you commit.

Initial cost plans and programmes let you compare buildings on a like-for-like basis and give you real numbers to negotiate terms against.

Design development and approvals – roughly 6 to 12 months out.
With a building chosen, design moves into detailed planning. Expect workplace strategy and briefing workshops, solidifying details like concept and layout (where meeting rooms, collaboration space and amenities will sit), as well as the technical design work like data cabling, fire strategy, acoustics and building regulations to start here.

It’s worth grounding this stage in what occupiers now expect from a high-performing workplace, to make sure you’re keeping your team happy. Our piece on commercial office design trends for future-ready workspaces is a useful primer.

By the end of this stage, you should have signed off design, price and programme.

Procurement and site works – typically 6 to 16-plus weeks.
Long-lead items (furniture, joinery, specialist AV, mechanical components) get ordered first, because they can outrun the on-site programme if they’re left too late. Site works then run from strip-out (if needed) through to partitions, ceiling and flooring, electrical and mechanical works, to furniture and styling.

Cat B projects can complete in 6 to 8 weeks; larger, more complex spaces often need 12 to 16 weeks or more.

Move-in and settling in – the final weeks and first three months.
Final testing and commissioning of building systems, IT, AV and access control, plus health and safety checks. Induction tours and clear launch communications help people use the space as intended, rather than defaulting to old habits in a new room.

In an ideal world, this stage is straightforward enough that your whole team is working as normal within hours of arriving, but if not, any snags are usually resolved over the first few weeks of occupation

Essentials you’ll need to bring to the first kick-off meeting

Your partner can guide you through every stage, but some inputs only you can provide. Having them ready early makes every design decision faster.

Business and people brief
Current and forecasted headcount, your hybrid working mode (how many people are likely in on a typical day, and what pattern you want to encourage), departmental adjacencies, and cultural goals such as more collaboration or a stronger client-facing presence.

If you haven’t worked out your numbers yet, how much office space do I need per person and our right-sizing checklist for hybrid work are both built for exactly this stage.

Technical and operational brief
IT, AV and security standards, any specialist spaces you require like labs or secure rooms, and any operational constraints like opening hours or delivery access.

Brand, experience, and ESG requirements
How you want people to feel walking in, plus sustainability priorities (natural light, material choices, energy performance, or certifications such as BREEAM or WELL where relevant). If retrofit rather than relocation is on the table, our sustainable office retrofit page covers what that route can achieve.

Constraints and non-negotiables
Budget range and whether there’s flexibility in it, lease commitments and obligations, and internal governance; who approves what, and how long that takes.

Where most fit-out projects usually lose time

Most of the frustrations that can crop up are both predictable and preventable.

Internal decision-making
This stalls projects more often than anything external does, usually because it isn’t clear who has authority to sign off design or budget, or because stakeholders arrive late with fundamental changes. Redesign, re-pricing and re-approval cycles can each add weeks to the timeline.

Landlord and third-party approvals
A necessary safeguard, but they slow things down when submissions are incomplete or a landlord’s own consultants need to review changes to building services or fire strategy.

Long-lead items
Core elements like furniture and joinery can outrun the on-site programme entirely if specifications aren’t locked in early. Nobody wants a finished office held hostage by a chair.

Hidden building constraints
Limited M&E capacity or unexpected structural elements can throw a spanner in the works. A thorough survey and due-diligence phase at the start of design catches most of this before it becomes a problem.

Five mistakes worth avoiding

Your partner can guide you through every stage, but some inputs only you can provide. Having them ready early makes every design decision faster.

1. Treating your fit-out as a late-stage task
   The day the ink’s dry on your contract is too late to discover that your new space can’t deliver your headcount or culture. Bring your fit-out partner in during building selection instead, so test fits and cost plans inform your process.
2. Focusing only on look and feel
   An office can look beautiful and still be a poor place to work if key factors like working styles, acoustics, lighting and air quality haven’t been considered. The office has to earn the commute, not just look good in the launch photos.
3. Setting budget before outcomes
   An arbitrary spend per square foot with no brief behind it tends to end one of two ways: overspending on things that don’t matter, or painful value engineering later that strips out the things people actually need. Define outcomes first, then align budget to them. Our guide to more cost-effective office fit-outs is a good starting point, and our fit-out cost calculator will get you a realistic Cat B range in a few minutes.
4. Underestimating the importance of change management
   A new office changes how people work. Skip the communication, and even a well-designed space meets resistance. Get it right and the numbers show it: TLT’s occupancy rose 20% after opening its Manchester office, and headcount 23%, because the space was designed around how people actually wanted to work. Read more on that here.
5. Ignoring future flexibility requirements
   Designing entirely around today’s headcount leaves you locked in, even if the business grows or changes shape. Modular furniture and reconfigurable settings buy you room to move without another full fit-out.

Designing entirely around today’s headcount leaves you locked in, even if the business grows or changes shape. Modular furniture and reconfigurable settings buy you room to move without another full fit-out.

Bringing it all together

An office fit-out isn’t the finishing touch at the end of a lease. It’s a structured process that starts up to two years before you move, shapes which building you can even consider, and touches everything from technology and culture to brand and ESG.

Understand who needs to be involved, when the decisions land, what to prepare and where projects usually stall, and a fit-out becomes a managed part of your lease expiry planning.

Still working out where to start?