Two budgets, two parties
| Level | Who carries it | What it covers |
|---|---|---|
| Shell and core | owner or developer | structure, façade, roof, circulation, common sanitary, primary services |
| Tenant fit-out | the occupier | partitioning, finishes, terminal services, built-in furniture |
A benchmark quoted for an office building may therefore describe one, the other, or both. The gap between the three readings is considerable, and it is the first cause of misunderstanding in this segment.
Before any comparison the question is therefore: does this price cover shell alone, fit-out alone, or the whole. A benchmark without an answer to that question is not usable.
The denominator question again
As in collective housing, several areas coexist, and property-market vocabulary does not coincide with construction vocabulary. Lettable and constructed areas differ appreciably.
Constructed area, lettable area and usable area do not cover the same thing. Circulation, sanitary accommodation, plant rooms and risers are treated differently depending on the convention adopted.
A benchmark related to lettable area is higher than one related to constructed area, since the numerator includes works excluded from the denominator.
This point is covered fully in the article on reference areas. The measurement methods are compared there one by one.
What weighs in offices
Three families dominate the gap with housing. They concern services, running costs and flexibility.
Services. Ventilation, cooling, electrical distribution, data, detection and security represent a markedly greater share of cost than in housing. This is the item that most distinguishes the two programmes.
Flexibility. A floor plate intended to be repartitioned several times over its life requires grids, spare capacity and service distribution that cost at construction and repay in operation.
The façade. It carries image, energy performance and visual comfort simultaneously. Its specification moves the benchmark considerably without any change of brief.
What retail adds
Retail shares the logic of offices but adds constraints of its own. The shopfront and public accessibility are the principal ones.
Access and flows. Deliveries, storage, public circulation and escape follow requirements that drive dimensions.
The shopfront. It is a technical element in its own right, with implications for security, thermal performance and exposure.
Activity-related equipment. Extraction, refrigeration, effluent treatment or specific electrical capacity belong to the operator rather than the shell, but determine the provisions to be allowed.
Ground-floor location in a mixed building adds acoustic and structural interfaces with the dwellings above.
Why a commercial benchmark transfers poorly
Three reasons make this segment less benchmark-friendly than housing. The benchmark serves there as an order of magnitude and not as a costing tool.
The brief is more heterogeneous. Two office buildings of the same area may have very different service levels.
Operation enters the equation. Design decisions are justified by operational savings, which a construction benchmark does not capture.
Regulatory requirements depend on use and occupancy, with thresholds triggering obligations on safety and accessibility.
What region and municipality add
As everywhere in Belgium, planning rules, land use and energy requirements belong to the regions. The three regions impose neither the same thresholds nor the same procedures.
In dense fabric, site access and party-wall constraints are added, weighing more heavily on an urban commercial scheme than on a peripheral build. This is covered in the article on Brussels.
Land use further determines whether office or retail use is possible at all on a given site, which is checked before any cost study. That check therefore precedes any economic feasibility study.
What this means for an estimate
Four rules.
Separate the two budgets from the outset. Shell and fit-out add up properly only if they were distinguished.
Name the reference area, stating whether it belongs to property or construction vocabulary.
Price services separately. It is the most variable item and the one most differentiating two apparently similar projects.
Check the permitted use before the cost. A perfect benchmark on a site where the use is not allowed serves no purpose.
This article reflects professional practice at the date of checking and serves as orientation. It does not constitute legal advice and does not replace assessment of the individual case.