flex office or assigned desks: which way of working should you choose?

The French Labour Code governs these choices through Article R4222-1 et seq. on ventilation, Article R4223-1 on lighting, and Article R4213-5 on noise. The EN 12464 standard sets average lighting levels to be maintained, ranging from less than 100 lux for unoccupied areas to several thousand lux for high-precision activities (AFE). Acoustic performance levels in open-plan offices are subject to a dedicated normative categorisation. The right way of working depends on the role, the actual presence rate and managerial maturity, never on a generic benchmark.

The Kytom method in 4 steps calibrated over 12 weeks

Our reading diverges from the dominant discourse of space planning software vendors on this specific point: a flex office is decided based on 8 weeks of measurement, never on a declarative survey alone. Internal surveys tend to significantly overestimate the desired presence rate compared to the rate actually measured: it is this delta that turns a theoretical flex at 0.75 into a flex at 0.90 saturated on Tuesdays.

The Kytom method structures the decision over an average period of 12 weeks, from audit to master plan, mobilising the design and works teams of the 11 agencies in France and Spain.

1. Usage diagnosis (2 to 3 weeks): badge data and internal survey to objectify attendance by day, floor and desk type.
2. Target workshop (1 week) with CFO, HR Director and Office Manager: three costed scenarios (optimised assigned desk, flex office at a 0.7 ratio, segmented ABW) with impact on m2/employee, OPEX and carbon footprint (Bilan Carbone method, carbon base v23.4).
3. Prototype on a pilot floor of 80 to 150 desks over 6 to 8 weeks, with adoption measurement and furniture adjustment.
4. Deployment and change management and approach.

Each deliverable includes a full cost per desk amortised over 9 years, a works schedule and an internal communication plan. Commercial spaces typically segment into two types: « sales/collaboration » (dynamic, bright clusters) and « engineering/concentration » (desks with acoustic partitions, noise level below 35 dB(A), bearing in mind that the Standard level of the NF S31-080 standard corresponds to the regulation and to the minimum functional level of acoustic comfort, with Kytom targeting the High level here).

When this method is not the right approach. Below 800 m2 or 60 employees, sensor instrumentation and a workshop over the standard timeframe cost more than the space savings generated: ROI over 5 years. For these formats, Kytom switches to a short diagnosis (badge data only, 3 weeks) without a prototype. Likewise, when the measured presence rate is very high for sales administration, support or production roles, flex becomes counterproductive and the full method is not justified: in that case the assigned desk is optimised through densification and acoustic treatment, without changing the ratio.

Measured benefits: space reduction, lower energy consumption and increased employee satisfaction

Furniture reuse, integrated into the majority of our recent projects, significantly reduces the carbon footprint per desk, drawing on the ADEME Carbon Base reference frameworks. The benefits observed generally cover a reduction in space, a decrease in energy consumption and an improvement in employee satisfaction, the scale of which varies depending on the context of each project.

Method

1. Measure actual occupancy
   Deploy presence sensors or use badge data over a minimum of 4 weeks. Do not rely on HR declarations: the gap with reality often reaches 15 points.
2. Map the roles
   Segment by BU the needs for confidentiality, document density and collaboration. This grid avoids dogmatic uniformity and reveals the areas where flex is relevant or inadvisable.
3. Simulate 3 costed scenarios
   Compare assigned desk, flex 0.7 and ABW on CAPEX, OPEX, 5-year ROI and CSRD impact. Include the cost of change management, often forgotten in initial estimates.
4. Test on a pilot floor
   Deploy the chosen scenario on 30 to 60 desks over 8 weeks. Measure satisfaction, actual usage and adjust the ratio before generalisation. This phase avoids 80% of errors.
5. Train managers and ambassadors
   Management by objectives is learned: plan for 2 to 3 days of training per manager. Identify 1 ambassador per 20 employees to relay operational adjustments on a daily basis.
6. Deploy in measured waves
   Spread the deployment floor by floor with usage measurement between each wave. Adjust signage, furniture and house rules at each stage. Avoid the big bang beyond 200 desks.