The four quantities
| Quantity | What it determines | Where it is governed |
|---|---|---|
| Chargeable costs | the fee basis | § 4 HOAI, determined under DIN 276 |
| Fee zone | the degree of difficulty | § 5 and § 35 HOAI |
| Fee table | the fee band | § 35 paragraph 1 HOAI |
| Work phases | the chargeable share | § 34 paragraph 3 HOAI |
The order is unavoidable. No chargeable costs, no table value; no fee zone, no band; no commissioned phases, no share.
Step one: chargeable costs
Chargeable costs are the fee basis. They derive from the cost calculation under DIN 276 but are not identical with construction costs: some cost groups count in full, some only under conditions, and some not at all.
Two particularities apply, and both change the result appreciably. They are regularly overlooked when a construction sum is carried straight into the table.
| Particularity | Rule |
|---|---|
| Technical installations | chargeable in full up to a threshold, at half above it |
| Value added tax | expressly not part of chargeable costs |
In existing buildings, the fabric being incorporated is added and must be appropriately taken into account, raising the fee basis. Its extent and its value are to be agreed.
The full system is covered in the branch on chargeable costs within the cost planning subject. It also sets out which cost groups enter in full, in part or not at all.
Step two: the fee zone
The fee zone reflects the difficulty of the task. For buildings and interiors there are five zones, from very low to very high design requirements.
For buildings, allocation follows six assessment criteria: requirements for integration into the surroundings, number of functional areas, design requirements, structural requirements, building services and fit-out. Interiors have their own catalogue.
A widespread misconception concerns the points method. It is not the standard route but applies only where criteria from several zones are applicable and doubt therefore arises. In the normal case, allocation follows directly from the criteria and the object list.
The system is covered in the article on fee zones. It also sets out when the points method comes into play at all.
Step three: the fee table
The fee table assigns a fee band to each combination of chargeable costs and fee zone. Since 2021 these bands are values for orientation rather than binding rates.
The lower figure of each band is the Basishonorarsatz, base fee rate. It matches the former minimum rate in amount but serves a different function: it applies as agreed where no agreement on the level has been made in text form.
Where chargeable costs fall between two table values, interpolation applies. The system is covered in the article on fee tables and the base rate.
Step four: the commissioned work phases
The table value corresponds to the fee for all nine work phases. Where not all are commissioned, only the percentages of the phases transferred may be charged.
Those percentages differ between buildings and interiors. The full overview sits in the branch on the nine work phases.
Where not all basic services within a phase are transferred, only the corresponding share is chargeable. Since the HOAI does not weight individual basic services, that share must be agreed. The article on partial commissions covers the procedure.
What comes afterwards
After the basic calculation, several supplements and reductions apply, and they act at different points. Where they act decides the outcome, since a supplement on the basis works differently from one on the fee already determined.
| Instrument | Acts on | Condition |
|---|---|---|
| Existing fabric incorporated | chargeable costs | appropriate consideration; extent and value to be agreed |
| Conversion supplement | the fee determined | conversion or modernisation; agreement in text form |
| Increase for repair work | the percentage for construction supervision | agreement in text form, up to 50 per cent of that phase |
| Repetition reduction | the percentages of phases 1 to 6 | several essentially identical objects |
| Ancillary expenses | separately alongside the fee | agreement, otherwise reimbursement on evidence |
The order is not arbitrary: existing fabric acts before the table is read, the conversion supplement afterwards. The article on the conversion supplement covers how they interact.
What has remained binding since 2021
The question is often asked and the answer is clear: nothing about the level of the fee is binding any longer. Fees are freely negotiable.
Two formal requirements have remained binding, and neglect of either leads to the base fee rate. Both concern the form and not the level.
| Requirement | Owed to |
|---|---|
| The agreement on the level, made in text form | every client |
| The notice, before the binding contractual declaration, that a higher or lower fee may be agreed | consumers only |
Both mechanisms are covered in the branch on fee agreements. It also explains why the consequence of the first cannot be rebutted.
Alternatives to the table fee
Since the level is freely negotiable, other remuneration models are permissible, particularly hourly rates and lump sums. They carry advantages and drawbacks depending on project type, and they change nothing about the duty to inform consumers.
The article on hourly rates and lump sum fees covers the trade-offs, and a worked example shows the full calculation on a concrete case. A worked example shows the full calculation on a concrete case.
Which cost determination governs
One point concerns the calculation as the project proceeds: which cost determination the chargeable costs come from. The answer changed fundamentally in 2009.
Since the 2009 revision the cost calculation model applies. The fee for all basic services is derived from the results of the Kostenberechnung, exceptionally from those of the cost estimate. The earlier stage-by-stage accounting, under which each phase rested on its own cost determination, has gone.
Three practical consequences follow. The second is the one that surprises clients most often.
| Consequence | What follows |
|---|---|
| The fee basis is fixed early | it arises in work phase 3, before a substantial part of the service has been performed |
| Later cost increases have no effect | where the project becomes more expensive without a change of scope, the fee stays unchanged; the final cost statement is a basic service but not the basis of fee determination |
| Changes of scope do have effect | where the scope changes by agreement and chargeable costs change with it, an adjustment in text form is provided for |
The distinction between the two is covered in the article on changes of scope. It also sets out the two conditions that must both be met.
The system of the cost calculation is covered in the article on cost calculation at the third level. It also sets out which bases the standard requires for it.
The commonest error
It concerns not the arithmetic but its basis: confusing construction costs with chargeable costs. It is also the one that works in both directions.
A client naming the construction sum generally means total cost or building cost. Chargeable costs are something else. Entering the wrong figure into the table yields a result either substantially too high or too low, and assailable in both directions.
The system of cost groups and their chargeability is covered in the branch on chargeable costs. It also carries the threshold rule for technical installations.
Related articles
This article reflects the position of the rules and case law at the date of checking and serves professional orientation. It does not constitute legal advice and does not replace assessment of the individual case.