How the benchmarks are constructed
The governing datasets present office buildings by standard level, customarily basic, mid-range and high, with supplementary categories by construction method such as a separate entry for timber. Refurbishments of existing buildings are carried separately.
The entries are consistently structured:
| Framework detail | Form |
|---|---|
| Reference quantity | gross floor area under DIN 276, December 2018 edition |
| Cost scope | building cost, that is cost groups 300 and 400 |
| Tax basis | including value added tax |
| Price date | given by quarter |
| Scatter band | from the standard deviation of the sampled projects |
| Regional basis | converted to the national average |
The last two points are decisive in use. The scatter band is not imprecision but the actual information: it shows how widely the completed projects sit around the mean. A benchmark with a wide scatter band demands more careful allocation than one with a narrow band.
Conversion to the national average means the figure applies at no specific location and must be adjusted with a regional factor. The system is set out in the article on regional construction cost differences.
Completion stage is the most important qualifier
Office schemes frequently do not deliver a fully usable building but a defined intermediate condition. Tenant-specific fit-out follows later, once letting is settled and according to each occupier's requirements.
| Completion stage | Scope | Effect on the benchmark |
|---|---|---|
| Shell and facade | structure, envelope, roof, circulation core | lowest figure, not usable |
| Base build | plus primary services, sanitary cores, lifts, basic lighting | mid figure, lettable as raw space |
| Full fit-out | plus partitions, floor finishes, ceilings, occupier installations | highest figure, ready for occupation |
Two benchmarks for the same building type and standard may therefore describe different degrees of completion. The gap between base build and full fit-out runs to an order that clearly exceeds any regional adjustment.
For your own cost estimate it follows that completion stage belongs in the same line as the benchmark, stating what it covers. The term base build is not standardised and is used differently across the market.
Space efficiency governs viability
For an office building, the building cost benchmark per square metre of gross floor area is a necessary but not sufficient quantity. What governs for an investor is cost per square metre of lettable area.
Between the two sits space efficiency, the share of usage area within gross floor area. It depends on several factors that are fixed early.
| Factor | Acts through |
|---|---|
| Circulation cores | their number and arrangement |
| Building depth and plan form | the share of internal zones |
| Office typology | cellular, combi or open plan |
| Building services | their space requirement |
| Construction type | wall thicknesses |
A design with an unfavourable core arrangement can deliver considerably less lettable area at an identical building cost benchmark. The difference acts across the whole life of the building, since it affects not only the investment but every subsequent rent.
Practical consequence: an options appraisal for an office building carries two benchmarks side by side, building cost per square metre of gross floor area and investment per square metre of usage area. Only the second answers the client's question.
The building services share
The share of cost group 400 within building cost is considerably higher in office work than in housing, and has risen further over the years. The drivers are ventilation and cooling plant, security and communications systems, conveying installations and increasingly building automation and charging infrastructure.
Datasets present individual plant groups separately and give two figures that must not be confused: the percentage share of the cost of building services, and the benchmark per square metre of gross floor area, the latter formed only from those projects where that plant was actually procured. For conveying installations, for instance, a single-digit percentage share sits against a benchmark in the low double-digit euros per square metre.
Missing that distinction means costing plant into a building that does not have it, or leaving it out of one that needs it. The error works in both directions and is invisible in the benchmark.
New build or refurbishment
A growing share of German office schemes concerns not new build but the upgrading of existing buildings. Datasets therefore carry refurbishments as a separate category, and the benchmarks are not comparable with new build.
Dispersion is considerably wider for refurbishments. The reason lies in the range of intervention depth: it runs from a pure tenant fit-out through replacement of the building services to full strip-out with complete renewal of facade and plant while retaining the structure.
Three items push costs in existing buildings above new build levels. They arise independently of one another and accumulate.
| Item | Why it costs more in an existing building |
|---|---|
| Structure | existing floors rarely designed for today's imposed loads or for routing today's services |
| Contamination | investigation, removal and disposal; the uncertainty falls only once the fabric is opened up |
| Storey heights | constrain suspended ceilings and raised floors, raising the cost of routing services |
Three items, by contrast, disappear entirely in an existing building. They narrow the gap to new build without closing it.
| Item | In an existing building |
|---|---|
| Foundations | omitted |
| Structural shell | largely omitted |
| Circulation cores | frequently omitted |
Against these sit savings that can be substantial: foundations, shell and frequently the circulation cores fall away. Whether refurbishment costs less than replacement therefore cannot be answered in general terms and belongs in a separate appraisal. The framework for intervention depths is set out in the branch on renovation costs.
Certification as a cost factor
For office buildings in the investment segment, sustainability certification is now the rule rather than the exception. It acts on construction cost through several routes.
The two routes land in different cost groups, and that is exactly where the use of third-party benchmarks fails. A third-party benchmark is therefore usable only where it names the route chosen.
| Route | Covers | Cost group | In the building cost benchmark |
|---|---|---|---|
| Direct | building envelope, plant, material selection, metering strategy | 300 and 400 | included |
| Indirect | documentation and evidence effort, certification fees | 700 | not included |
For cost estimating it matters that the two parts are carried separately. The additional construction work belongs in cost groups 300 and 400 and is part of the building cost benchmark. The evidence effort belongs in cost group 700 and is precisely not inside the building cost benchmark. A benchmark drawn from a sample of certified projects contains the one and not the other.
Other common reference quantities
Two further measures are customary in office work alongside gross floor area. Both produce markedly different figures from gross floor area.
| Reference unit | When it holds | What it depends on |
|---|---|---|
| Per workstation | when the occupier rather than the investor decides | office typology and space allowance per workstation |
| Per m³ gross volume | when storey heights depart from the norm | representative entrance areas, conversions with large clear heights |
Neither measure replaces the area benchmark; they check it. Where the results diverge sharply, unusual geometry or an unusual occupancy density is almost always the cause.
Related articles
The orders of magnitude given are indicative values for Germany. They do not replace a project-specific cost estimate and vary considerably by standard, completion stage, plant scope and region.