Hybrid working has changed how offices are used, but not necessarily how large a share of expenses they take up.
Many UK businesses now have fewer people in the office than their leased space was originally designed for, increasing the cost of office underutilisation and raising questions about whether their footprint fits the way they work.
Rather than treating this as an all-or-nothing lease decision, organisations are now exploring a “core + flex” approach. This is where you combine a permanent office with flexible workspace that can adapt to changing attendance.
This guide explains how to identify the cost of under-utilised office space and assess whether a core + flex model could be a better fit for your business.
How big is the under-utilisation problem in UK offices?
Office underutilisation often creeps up gradually.
A few empty desks on a Monday or Friday might not feel significant on their own. But the same pattern repeating week after week? That points to a much bigger mismatch between the space you’re paying for and the space your business actually uses.
For many property and workplace leaders, that’s where the conversation pivots. Instead of asking, “Are people coming into the office often enough?”, the more helpful question becomes, “Does our office footprint still reflect the way our business operates today?”
Attendance vs leased capacity
Most office leases are signed with the future in mind. Space is planned around expected growth, hiring plans and the busiest days a business expects to accommodate, not average attendance over the course of a week.
As organisations evolve, those assumptions can change. A footprint that once felt appropriate may gradually provide more capacity than the business consistently needs, even though headcount remains the same and the office continues to play an important role.
The result is a growing gap between leased capacity and regular attendance that’s often difficult to spot until utilisation is viewed over a longer period.
Translating empty desks into cost
When attendance and leased capacity begin to drift apart, the monthly office bill might not change, but the value you’re getting from that space does.
That’s because many of the biggest costs attached to a leased office are fixed. Rent, service charge and business rates continue throughout the lease, while the upfront costs of designing and fitting out the space has already been invested.
For example, imagine your office costs £500,000 a year and was originally planned around regular use from 100 employees. If attendance patterns change and the space regularly supports closer to 50 people, the cost of the office stays exactly the same—but it’s now supporting a much lower level of usage.
That’s why many property teams look at effective cost per occupied desk. It helps translate office utilisation into a clearer commercial metric, even when the lease itself is based on square footage.
There are longer-term property considerations too, including EPC and MEES requirements, lease breaks, dilapidations and potential fit-out write-downs. By understanding these factors alongside day-to-day utilisation, you’ll get a clearer sense of overall space efficiency and whether your current footprint still makes commercial sense.
The case for core + flex
Once you understand how your office is being used, the next step is deciding which parts of your workplace need to stay fixed and which parts need more flexibility.
That’s where a core + flex model can help. Think of your “core” as the permanent workspace your business needs day to day, and your “flex” as the additional space you can access when needs change, such as busier periods, short-term projects or different locations.
For example, a business might keep a smaller central office as its core, while using flexible workspace to support peak attendance days, temporary projects or employees working in different locations.
“One of the biggest shifts we’ve seen is in how businesses think about their leased office. It used to make sense to plan around the busiest day of the week because attendance was much more predictable. Today, many businesses are finding they don’t need permanent space for every possible scenario. A core + flex approach helps separate the space you know you’ll use regularly from the space you only need occasionally, making it much easier to match your office footprint to the way people actually work.” — Tushar Agarwal, CEO and Co-Founder at Hubble
What ‘core’ should cover
Your core office should support the parts of your business that are predictable. That might include teams that regularly work together, recurring collaboration days, client-facing areas or specialist facilities your employees rely on.
Because these requirements are more consistent, they usually make sense as part of your permanent workspace. The aim is to build your core around consistent demand, rather than the highest number of people who might use the office occasionally.
But workplace demand isn’t always predictable. Even with the right core office in place, there will be times when your business needs more space, different locations or extra capacity. That’s where flex comes in.
What ‘flex’ adds
Flexible workspace supports the needs that are harder to predict. This could include extra capacity during busier periods, temporary, on-demand space for project teams or access to satellite locations outside your main office.
Instead of committing permanent space for requirements that only happen occasionally, flex gives businesses another way to respond when workplace needs change.
Together, core and flex create a workplace model built around how space is actually used: a consistent base for regular demand, with access to additional workspace when it’s needed.
TL;DR
| Core | Flex |
| The permanent workspace that supports predictable demand, such as regular team attendance, collaboration and business-critical facilities. | Your flexible approach which gives you access to additional workspace when requirements change, such as project space, busier office days or satellite locations. |
How to size core vs flex
There’s no single formula for sizing a core + flex model, but a few simple sense-checks can help you build an office footprint around how your business actually works.
Start with average attendance, not just your busiest days. A high office occupancy rate once or twice a week doesn’t necessarily mean your permanent workspace needs to accommodate those peaks all year round.
Next, look at how different teams use the office. Some need a regular base because they collaborate frequently or rely on specialist facilities, while others have more flexibility in where they work.
Those patterns can help you decide what belongs in your core and where flexible workspace adds the most value.
Finally, think ahead. Growth plans, project work and changing headcount can all affect future demand. Building some flexibility into your office footprint makes it easier to adapt without committing to permanent space before you know you’ll need it.
Risks and trade-offs
Like any workplace strategy, a core + flex model comes with a few trade-offs to consider.
One of the biggest considerations is employee experience. If teams spend most of their time working across different locations, it can become harder to maintain a consistent workplace experience and a shared sense of company identity.
That’s why the core office should remain the place where people come together to collaborate, build relationships and connect with the wider business.
There are property considerations too. Reducing a leased office footprint isn’t always straightforward, particularly if you’re tied into a long lease.
Break clauses, fit-out write-downs and dilapidations can all affect when you’re able to make changes (and how much those changes cost) so it’s worth understanding these before adjusting your long-term strategy.
Finally, flexible workspace isn’t one-size-fits-all. Contract terms, notice periods and included services can vary between providers, which means two similar-looking workspaces may offer very different levels of flexibility.
Checking exactly what’s included upfront can help avoid unexpected limitations later on.
From audit to decision
If you’re considering a core + flex model, the best place to start is with your current office.
Begin by measuring how your workspace is actually being used. Understanding average attendance, peak occupancy and team-by-team usage will give you a much clearer picture of how your office supports the business today.
From there, compare your office costs against that level of utilisation. Looking at your effective cost per occupied desk can help highlight where your current footprint is working well and where there may be opportunities to improve space efficiency.
The next step is to test what a core + flex split could look like. Identify the space your business relies on consistently, then consider where flexible workspace could support changing demand, whether that’s additional capacity, project space or satellite locations.
Finally, review your workplace strategy regularly. As your business grows, projects change and attendance patterns evolve, your workspace should evolve with them.
Ready to explore your options? Browse Hubble’s London office spaces to compare permanent offices and flexible workspace in one place.
