Construction in occupied premises: transforming without interrupting your business
Four critical interfaces we arbitrate simultaneously
Vacating a 1,500 sqm floor for 14 weeks of work means 550,000 to 800,000 EUR of rent gone and a double relocation to orchestrate. Maintaining operations during the works generates a limited cost overrun, with no comparison to the cost of a double relocation and a floor left vacant for several weeks. The financial trade-off almost always favours continued occupancy, and our client finance departments are now convinced of it: the majority of the operations we manage now take place in occupied premises. We take charge of mapping the incompatibilities between your business cycles and the work sequences, phasing in lots of 200 to 400 sqm, daily coordination with your operations team and continuous acoustic monitoring. Since 2006, we have consolidated a 5-step method aligned with regulatory acoustic thresholds and article R4227, enforceable before your inspection body (Apave, Bureau Veritas, Socotec). Here are the four interfaces we arbitrate simultaneously and the financial mechanism that turns your occupancy constraint into preserved cash flow.
our approach
Working on your active floor without degrading your productivity requires holding four tensions at the same time. Poor anticipation generates significant cost overruns and schedule slippages that compromise operational continuity.
| Interface | What we manage | Reference |
|---|---|---|
| Temporal | Aligning phases with your business cycles (accounting close, sales waves, sensitive HR periods), staggered hours 6pm-11pm or extended weekends | Client business cycles |
| Spatial | Sealed airlocks, mobile acoustic partitions, buffer zones below 55 dB(A) | NF S 31-080 |
| Logistics | Deliveries before 8am, dedicated freight lifts, buffer storage in the basement, flows separated from occupants | Kytom logistics charter |
| Safety | Permanent maintenance of exits, access to main switchboards, network racks, smoke extraction | Kytom safety standard |
Our reading, validated on 1,200+ projects: accelerating an occupied site by 2 weeks costs more than extending it by 4 weeks with reduced interruptions. The cost overrun of staggered hours, labour reinforcements and permanent monitoring exceeds the saving in rent avoided as soon as your operations continue. The right metric is not gross lead time, but the total cost including disruption.
When this four-interface grid does not apply. Below 300 sqm on a floor with fewer than 30 occupants, the formalism becomes oversized: the mapping takes more time than the works. Vacating over 3 to 5 working days then costs less than phasing engineering. The method regains its full relevance from 500 sqm or when your business prohibits any closure window (trading floor, continuous-flow call centre, laboratory).
your financial gains
Converting your occupancy constraint into preserved cash flow
The trade-off between occupied premises and temporary vacancy is first and foremost a financial calculation, not a technical choice. On a 1,500 sqm office floor in the Paris CBD, vacating for 14 weeks represents 380,000 to 525,000 EUR of lost rent (based on 750 to 1,000 EUR/sqm/year excl. tax), plus 60 to 90 EUR/sqm/month for transitional rehousing and 45,000 to 80,000 EUR for a double relocation. Total vacancy: 550,000 to 800,000 EUR.
This compares to the cost overrun of maintained occupancy, generally estimated between 8 and 12% of the works cost, i.e. 60,000 to 180,000 EUR on a renovation budget of 1,200 EUR/sqm. The gap of 4 to 6 against 1 explains why your finance departments now examine maintained occupancy as the default scenario, and vacancy as an exception justified by the criticality of the works.
For your Asset Manager, the stakes shift towards asset value. A building renovated without operational disruption retains its occupancy rate and its effective rent index, whereas a 14-week vacancy breaks derogatory leases and weakens negotiation at renewal. The tertiary decree also imposes energy performance milestones that lend themselves poorly to long closure windows: we phase in lots of 200 to 400 sqm to spread your CAPEX over 18 to 24 months without an unfavourable accounting shift.
operational vigilance
Three recurring mistakes that concentrate occupant complaints
Three pitfalls regularly compromise construction projects in occupied premises. We have mapped them across our portfolio and calibrated our countermeasures.
- Underestimating acoustic impact. Decibels travel through your light partitions and modular suspended ceilings, even with standard protections. We conduct a preliminary acoustic audit according to our internal standard, which guides the choice of mobile screens, perimeter sealing and time slots for noisy tasks (concrete drilling, demolition). The thresholds adopted in buffer zones remain below 55 dB(A), consistent with a sound environment compatible with intellectual work.
- Neglecting utility management. An unscheduled cut to electricity or air conditioning immediately interrupts your business. We install temporary bypasses and schedule switchovers in slots validated with your facility manager, generally between 6am and 7:30am.
- Communicating too late with your occupants. Unannounced disruptions are the leading source of tensions raised by Office Managers.
Our setup combines a weekly schedule issued 7 days in advance, an identified on-site works contact and a dedicated hotline handling emergencies within 30 minutes. This protocol significantly reduces the volume of complaints compared to projects without a structured communication unit.
Limit of the setup. On projects of less than 6 weeks with fewer than 50 occupants affected, the 7/7 hotline and the dedicated contact generate a disproportionate coordination cost: a weekly meeting with your Office Manager and an email 3 days in advance are sufficient. The structured unit becomes essential beyond 8 weeks or 100 occupants concerned.
Method
- Audit of operational constraints
We map your critical hours (accounting closes, sales waves, sensitive HR periods), your sensitive zones (server rooms, client areas, executive floors) and your vital equipment (main switchboards, network racks, smoke extraction). This diagnosis, carried out over 2 to 3 weeks, combines an interview with your Office Manager, a technical visit with your facility manager and a preliminary acoustic audit, compliant with the standard applicable to the acoustic performance of open-plan office spaces. - Adaptive phasing in lots
We divide your project into lots of 200 to 400 sqm according to the business sensitivity of the zones. This sequencing allows you to spread your CAPEX over 18 to 24 months, to meet the regulatory milestones applicable to office property and to keep a majority of floors operational at each phase. The phasing plan is validated on a contradictory basis with your real estate department and your operations team. - Reinforced daily coordination
Our site manager holds a daily meeting with your operations manager, in addition to the weekly client meeting. This short rhythm allows real-time arbitration of schedule adjustments, utility cuts and unforeseen interventions, without escalating to a formal steering committee at each incident. - Acoustic and dust monitoring
We install acoustic and dust probes continuously in buffer zones, with thresholds set at 55 dB(A) in the adjacent office zone and occupational exposure limits for inhalable dust. Exceedances trigger an immediate stop of the task concerned and rescheduling outside occupancy hours. - Occupant feedback loop
We distribute a weekly schedule 7 days in advance to all your occupants, identify an on-site works contact reachable on site and activate a dedicated hotline handling each emergency within 30 minutes. The weekly reporting sent to your Office Manager consolidates incidents, complaints and corrective actions undertaken.
