Why the ranges diverge so widely
Four causes, cumulative, account for the entire dispersion. They are checked one after another before any comparison.
| Cause | Scale of effect |
|---|---|
| VAT included or not | 21 % on new build |
| Fees and ancillary costs included or not | substantial item |
| Completion stage adopted | closed shell to turnkey |
| Reference area | gross or net, gap of around 15 % |
A source quoting about 2,400 euros per m² including VAT and architect, and another quoting 1,200 euros per m² excluding tax at closed shell, may describe the same building. Only the calculation conventions separate them.
Before comparing two figures they must therefore be brought to a common basis. The method is covered in the article on comparing two quotes.
How to read a published range
Four questions, asked systematically and in this order. The order matters, since each answer conditions the next.
Excluding or including VAT. The gap is 21 % on new build, enough to reverse a comparison.
Which stage. A closed-shell price and a turnkey price differ by roughly a factor of two.
Which costs included. Architect's fees, studies, connections and kitchen are sometimes integrated, sometimes excluded, and rarely flagged.
Which area. The common Belgian convention is gross area, wider than net.
A range that does not answer those four questions is not usable, however reputable its source. It gives an order of magnitude without a scope, and so without any check.
The four project types
Each type follows a different cost logic, not merely a different price level. Benchmarks therefore do not carry over from one type to another.
The new detached house is the best-documented case and the one where source dispersion is greatest. Construction method, traditional or timber frame, plays an important role.
The apartment building introduces items absent from houses: common parts, circulation, acoustic requirements between dwellings, fire safety and, above a certain height, vertical transport.
Offices and retail are considered at two distinct levels, the shell delivered by the developer and the fit-out specific to the occupier, which belong neither to the same budget nor to the same party.
Major refurbishment has the widest range, because the unknown lies in the existing fabric and emerges during the works.
The scale effect applies throughout
A constant phenomenon belongs here.
The price per m² falls slightly as area increases, because foundations and roof do not track habitable area proportionally, unlike partitions and finishes. The effect is regular and therefore predictable from the sketch stage.
A benchmark from a small project applied to a large one therefore overstates. The reverse understates, which is more dangerous.
What the region adds
Construction ranges vary less between regions than land ranges, but the region weighs through other channels. The region acts mainly through periods, requirements and land values.
Energy requirements, consent periods and available support differ, and land values vary considerably, with marked gaps between the major conurbations and less pressured areas. Those gaps are established before any regional range is set.
A total budget is therefore far more regional than a construction benchmark. This is covered in the branch on regional cost.
What this means for an estimate
Three rules.
Never carry a range without its convention. A range detached from its assumptions is a wrong figure, not an approximate one.
Normalise before comparing. Bring figures to the same stage, the same area and the same VAT treatment.
Use the range to check, not to price. A benchmark tests whether a brief fits an envelope; it does not replace measurement.
The articles in this branch
The article on the new detached house gives ranges by stage and the factors of variation. It is the best documented segment of the Belgian market.
The article on apartment buildings covers the scale effect and items specific to collective housing. Common parts form an item absent from the detached house.
The article on offices and retail separates shell from fit-out. The distinction governs who pays for what between landlord and occupier.
The article on major refurbishment covers dispersion and the trade-off against rebuilding. Dispersion is wider there than in new build.
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.