Office technical room fit-out: complete guide

A standard office floor plate generally includes 4 to 6 technical rooms with distinct requirements, each subject to specific regulatory frameworks. The main LV switchboard falls under NF C 15-100, with a minimum front clearance of 70 cm and ventilation sized to the dissipated power. The server room follows the professional recommendations of the IT industry (temperature range 18 to 27 °C, humidity 40 to 60%), incorporated into our technical specifications. Paper archives load the slab to 250 or 600 kg/sq m depending on the operating load adopted, versus 250 kg/sq m for standard offices. Cleaning and waste rooms require wastewater drainage and specific ventilation.

The Labour Code (articles R. 4216-1 to R. 4216-32) sets the rules for clearances and smoke extraction. Fire compartmentation requires EI 60 fire doors on access points to floor plates larger than 500 sq m, with coordinated triggering through a category A fire safety system (SSI). The amended order of 25 June 1980 also governs ERP premises. Annual Q18 inspections apply to high-risk rooms, a point to anticipate from the design stage.

Our reading differs from the dominant discourse on one point: NF C 15-100 does not require a dedicated LV switchboard room below 36 kVA installed. Industry conventional wisdom systematically pushes towards a closed room, for ease of execution. In practice, on the floor plates under 400 sq m we deliver, the technical cabinet enclosed in a ventilated 2 sq m cupboard complies with the standard and frees up 6 to 10 productive sq m, i.e. 300 to 500 EUR/sq m/year of recovered rent depending on the zone. On the office floor plates we audit, a significant proportion show at least one structural upgrade to anticipate: insufficient floor load for dense archives, saturated vertical risers, no dedicated low-voltage current room.

For the CFO and Asset Manager: what technical rooms really cost

On a Paris CBD floor plate at 750 EUR/sq m/year, 60 sq m of technical rooms represent 45,000 EUR of non-productive annual rent. The trade-off is therefore not « how many sq m do we allocate? » but « which technical-to-productive area ratio maximizes the value of the leased sq m? ».

Three quantified levers for the Asset Manager:

• Densification of the technical room: reducing the share of technical area on an 850 sq m floor plate can free up several dozen square meters, directly convertible into productive area and recovered rent. A trade-off to be quantified case by case according to the target ratio adopted, with the redensification CAPEX (floor reinforcement, cabling reorganization) running around 25,000 to 40,000 EUR at this scale for a 2 to 3 year ROI.
• Free-cooling on the IT room: significantly reduces the consumption of chillers, generating estimated savings of between 800 and 2,200 EUR/year in OPEX on a 4-rack room. Eligible for CEE BAT-TH-141.
• Tertiary decree: the consumption of technical rooms (IT cooling, permanent lighting) is included in the reduction base (−40% by 2030, −50% by 2040). A non-optimized server room compromises the trajectory of the entire building.

For the CFO, the CAPEX/OPEX trade-off hinges on the redundancy level: moving from N to N+1 significantly increases infrastructure cost but reduces the risk of unavailability. As an indication, the cost of one hour of downtime for an SME can quickly exceed several thousand euros on a critical activity, making the return on investment of N+1 redundancy very fast, but irrelevant for non-critical activities.

design and build method: 5 steps planned over 12 weeks

The Kytom sequence structures the design of technical rooms over a standard timeframe of 12 weeks, organized into 5 steps:

1. Technical audit (3 to 5 days): survey of the existing situation, verification of floor loads according to the Eurocodes applicable to actions on structures, measurement of the power available at the main LV switchboard, check of smoke extraction conditions.
2. Programming: sizing by industry ratios, i.e. 0.8 to 1.2 sq m per workstation for active archives, 15 to 25 sq m for a server room with 4 42U racks.
3. Detailed design: power/low-voltage current plans, fluid schematics, thermal balance on the dissipated load, choice of EI 60 or EI 120 partitions.
4. Execution: management of trades through the regional agency network, under a documented quality process.
5. Acceptance: COPREC testing, clearing of reservations within 15 days, digital DOE file with fire rating certificates and commissioning reports.

The redundancy levels (N, N+1, 2N) are decided during programming according to IT criticality, and directly determine the electrical balance and the room’s surface area.

When this approach is not the right one. The integrated design and build method loses its value below 8 sq m of combined technical rooms (typically floor plates < 250 sq m with a single mixed room): separate project management coordination is enough and the audit package weighs too heavily in the budget. On dedicated data centers of Tier III or IV criticality (PUE < 1.4 target, 2N redundancy), you should turn to a pure IT specialist, as Kytom only handles SME and head office server rooms up to 50 racks. Finally, if the residual occupancy of the floor plate is less than 4 years, the ROI of a heavy renovation does not pay off: prefer a short-term palliative (auxiliary air conditioner, additional rack in colocation).

Ratios, measured gains and points of vigilance

Well-sized technical rooms make it possible to recover significant area on the floor plate, convertible into workstations or meeting rooms. An IT availability rate above 99.9% equates to less than 9 hours of incidents per year. The return on investment of a renovation generally lies between 4 and 7 years, depending on equipment density and the redundancy level adopted.

Three pitfalls recur on renovation projects: underestimation of floor load in archives (250 kg/sq m instead of the 600 kg/sq m required), absence of a dedicated low-voltage current room (sharing with the main LV switchboard, non-compliant with NF C 15-100), IT thermal balance based on nominal power rather than actual dissipation, a discrepancy frequently observed during the audit phase.

Method

1. Audit of technical needs
   List your needs for electrical power, network throughput, archive volume and maintenance frequency. Quantify foreseeable developments over 5 years (densification, electric vehicles). This audit determines the sizing of each room.
2. Programming and layout
   Position the technical rooms centrally to limit cable lengths. Keep them away from focus areas (noise nuisance) and water points (risk of damage). Validate the floor load with a structural engineering office.
3. Coordination of technical trades
   Synchronize electrician, fluids, HVAC and low-voltage currents through a weekly meeting. Anticipate penetrations, provisions and commissioning. Kytom manages this coordination in design and build mode to avoid rework.
4. Testing, compliance and after-sales service
   Carry out commissioning tests (main LV switchboard, server cooling, fire detection), obtain Consuel and SSI certificates, train your teams. Kytom provides responsive after-sales service over 12 months for post-delivery adjustments.