Building services: multi-trade coordination and technical trade-offs

Mapping the interfaces structures every building services project in the office sector. Our project feedback identifies five systematic friction zones that determine the quality of the technical coordination:

1. Plumbing / electrical: positioning of distribution boards, minimum distance to water risers, sealing of penetrations through service ducts.
2. HVAC / lighting: trade-offs on ceiling heights with a minimum of 2.50 m clear, positioning of diffusers versus light fittings, access to balancing valves.
3. Structural works / services: openings sized with margin, penetrations in load-bearing zones validated by the structural engineering office.
4. Suspended ceilings / maintenance: access hatches every 6 linear m, permissible load of 600 x 600 mm tiles.
5. Fire safety system (SSI) / smoke extraction: EI 60 compartmentation on floor plates over 500 m2, IT 247 coordination with the category A SSI in accordance with NF S 61-931.

The management trade-off determines the outcome. In a traditional approach, each trade optimises its own scope. In the integrated method applied by Kytom under design and build, a single coordinator drives the 3D coordination and arbitrates detected conflicts in real time.

Kytom contrarian position. The industry consensus holds that systematic 3D coordination has become the norm. Our reading differs: on recent office projects, poorly positioned 3D coordination (too late, without arbitration governance) costs more than rigorous 2D coordination carried out at the schematic design (APD) stage. It is the timing of the coordination, not its tooling, that produces value.

When this integrated coordination logic is not relevant. Below 400 m2 on a newly delivered floor plate, with no rework of risers and no category A SSI constraint, collaborative 3D coordination costs more than it saves: 2D sequencing is sufficient. Likewise, on a refurbishment with no intervention in the plenum, the interface matrix becomes a formal deliverable with no operational value.

For the CFO and Asset Manager: the real cost of late services coordination

The industry treats building services as a technical matter. For the office decision-maker, it is first and foremost a cash-flow and asset-value issue. Three business perspectives structure the trade-off:

For the CFO: the arithmetic of rework. A services conflict detected during execution costs 3 to 5 times more than a correction at the design stage, a gap consistently observed across our projects. On a project at 250 EUR excl. VAT/m2 and 1,500 m2, a major reworking operation (relocating a riser, repositioning an AHU) represents 40,000 to 80,000 EUR in direct additional cost, excluding schedule slippage. Schedule slippage simultaneously mobilises 4 to 6 trades and triggers delivery delay penalties that weigh directly on the incoming tenant’s OPEX.

For the Asset Manager: the 20% technical contingency as an asset-value premium. Under-sizing the openings saves 2 to 4% of the initial cost but blocks any change of use over 5 years. On an office asset with a median holding period exceeding 7 years, this initial saving is paid for through heavy restructuring at the next lease. The ratios observed across our portfolio show that a contingency sized at 20% pays for itself as soon as the first significant change of use occurs: change in density, addition of equipped meeting rooms, integration of a shared kitchen.

For the Office Manager and the real estate department: maintenance accessibility. Optimising the footprint at the expense of operations generates recurring operating overheads that our project feedback consistently confirms, and that the asset’s holding period mechanically amplifies.

The financial reading reverses the order of priorities: it is not investment savings that drive the services trade-off, it is operating charges and flexibility of use.

Three on-site tensions that generate the majority of rework

Three pitfalls recur across the majority of office renovation projects monitored by Kytom:

• Late coordination. Deferring 3D coordination until after equipment ordering is the leading cause of on-site rework. Conflicts detected during the execution phase cost significantly more than a correction at the design stage: intervening early remains the most effective lever for savings.
• Under-sizing of openings. Calibrating too tightly deprives the building of any capacity to evolve. Real estate departments now require a 20% contingency on duct sections and distribution boards, in line with the practices relayed by ARSEG.
• Neglected maintenance accessibility. Optimising the footprint at the expense of operations generates significant operating overheads, regularly observed on the office sites we support post-delivery.

The operational response rests on three commitments: 3D coordination from the schematic design (APD) stage, validation of interfaces by the facility management teams before tender (DCE), and scalable sizing documented in the as-built file (DOE). This discipline avoids degraded trade-offs in the middle of the works phase, where each day of delay mobilises 4 to 6 trades simultaneously and amplifies the marginal cost of corrections.

Limitation of the approach. On a project with a use lifespan of less than 3 years (transitional space, building awaiting demolition), over-sizing the openings becomes economically counterproductive: the technical contingency does not pay for itself. In this case, strict calibration to current needs remains more rational.

Technical coordination methodology in four sequenced steps

The Kytom method is organised around four steps contractualised from the outset:

1. Audit of existing constraints. Surveyor’s measurements, 3D scan of plenums, identification of retained networks, connection points to risers. This phase generally lasts 2 to 3 weeks on a 1,000 m2 floor plate, depending on the complexity of the existing networks.
2. Interface matrix. Formalisation of the 5 friction zones (plumbing/electrical, HVAC/lighting, structural works/services, suspended ceilings/maintenance, SSI/smoke extraction), cross-validation with the inspection office (Apave, Bureau Veritas or Socotec depending on the contract).