Team Conversion

Office conversion feasibility study: secure your decision before capex

1 billion m² of tertiary building stock: the boundaries of your decision

400 to 1,800 €/m² of capex committed on an asset manager’s intuition: this is the standard error margin produced by a conversion launched without a structured feasibility study. The tertiary decree (-40% by 2030, ADEME’s OPERAT scheme) makes this decision non-deferrable, but the profession’s conventional wisdom still treats it as a technical audit. Our reading differs: the office conversion feasibility study is first and foremost an investment committee tool, not an architect’s deliverable. Kytom structures it in 6 to 8 weeks, on floor plates averaging 850 m² and up to 18,000 m² for complex assets. Deliverables: multi-criteria matrix, 2 to 3 programmatic scenarios costed to ±15%, Gantt schedule, ISO 9001 compliance, submittable to engagement committees above 1M€.

The French tertiary building stock represents approximately 1 billion m² according to ADEME (Chiffres-clés du bâtiment, 2023 edition). Within this stock, a significant share of the assets we diagnose in upstream missions turns out to be obsolete or under-occupied. The tertiary decree imposes -40% energy consumption by 2030, -50% by 2040 and -60% by 2050 relative to a reference year after 2010, in accordance with the OPERAT scheme (ADEME, OPERAT platform, 2023 data). In parallel, INSEE notes in its Tableaux de l’économie française 2024 a strain on the Ile-de-France office real estate market, with a vacancy rate above 10% since 2023 according to leading real estate brokers.

For an asset manager, the decision between three trajectories hinges on considerable differences in market value:

heavy renovation preserving tertiary use;
conversion to residential, hotel or serviced-residence use;
as-is sale at a discount.

We measure these differences case after case across our recent portfolio. Kytom frames technical feasibility (structure, grids, facades), regulatory feasibility (PLU, ERP, accessibility, Labour Code compliance R4211 to R4217) and economic feasibility. A structured upstream study eliminates most of the budget overruns observed at the construction phase, and makes investment committees reliable ahead of any engagement above 500K€.

Contrarian position. Contrary to the widespread practice that systematically favours residential conversion as soon as tertiary vacancy exceeds 10%, our reading of the decisions we lead is more nuanced: in a non-negligible share of cases, heavy tertiary renovation with ESG repositioning delivers an IRR higher than residential conversion, subject to a constraining PLU or a high regulatory clearance cost. Change of use is not the default option, it is the exceptional option.

How much does a Kytom office conversion feasibility study cost?

The cost of a conversion feasibility study varies with the asset’s surface area. Kytom observes a budget of 25 to 40K€ excl. VAT for an 850 m² floor plate, and 60 to 120K€ excl. VAT for an 18,000 m² asset. This amount remains marginal relative to the asset’s value and makes investment committees reliable ahead of any engagement above 500K€.