The principle
The central provision is brief and far-reaching in its consequences. The work is to be described clearly and so exhaustively that all firms must understand the description in the same sense and can calculate their prices reliably and without extensive preliminary work.
Three requirements sit within that sentence, each with its own function. They are cumulative and cannot be traded against one another.
| Requirement | Meaning | Function |
|---|---|---|
| Clearly | only one reading may be possible | a description permitting two readings produces tenders that are not comparable |
| Exhaustively | nothing material may be missing | what is not described cannot be priced |
| In the same sense | comparability of tenders is the objective | the principle serves not only the individual tenderer but competition |
A supplement is added, framed as a duty to establish the facts. To enable proper pricing, all circumstances influencing it are to be established and stated in the tender documents.
The unusual risk
The most consequential sentence of § 7 limits the transfer of risk. No unusual risk may be imposed on the contractor for circumstances and events over which they have no influence and whose effect on prices and periods they cannot estimate in advance.
The definition contains two cumulative elements: no influence and no foreseeability. Both must be present.
Typical cases are unknown ground conditions, unclear existing fabric, open consent requirements and market risk. Case law has also treated price increases arising from external events as an unusual risk.
The practical effect is an allocation of risk. What the client knows or can establish belongs in the tender documents. What they do not state cannot be shifted onto the tenderer, and attempting it produces either risk premiums in the tenders or variations during construction.
The article on clear and exhaustive specification covers the application. It also carries the forms of words that regularly breach the principle.
Two forms of description
The VOB/A recognises two routes, differing fundamentally in who supplies the design. The choice falls before tender preparation begins.
| Bill of quantities | Performance specification | |
|---|---|---|
| Design | prescribed by the client | put out to competition |
| Quantities | measured by the client | wholly or partly left open |
| Comparability | direct price comparison possible | comparison across concepts |
| Precondition | complete design | expediency after weighing |
| Default case | yes | exception |
| Route | Who supplies the design | Condition |
|---|---|---|
| The bill of quantities, the default | the client | the scheme is fully designed and an unambiguous schedule of quantities exists |
| The performance specification, the exception | the tenderer | it is expedient, after weighing all circumstances, to put the design out to competition as well |
The two articles on the bill of quantities and the performance specification cover them in detail. They also set out how the choice affects cost control.
Which item types are impermissible
Two item types are expressly restricted by the VOB/A, and both are regularly used in practice. They are symptoms of incomplete design rather than its solution.
| Item type | Restriction | Reason |
|---|---|---|
| Provisional items | as a rule not to be included | their execution is open at tender; they distort price comparison because one tenderer may price them high and another low |
| Attached daywork | only to the extent strictly necessary | a high proportion moves price formation out of competition and into execution |
A checking question follows for every item: is its execution certain, and has its quantity been measured. Where the answer is no, the reason should be established, and it almost always lies in incomplete design.
Technical specifications
A separate body of rules concerns references to technical specifications. The principle is that no product specification may be made that excludes competition.
In practice, references to standards, approvals and specifications must always carry the addition that equivalents are admitted. The relevant standards provide a form of words to be included in the preliminaries to the bill of quantities.
Its absence is a procurement defect and open to challenge. The system is covered in the article on DIN 18299.
The link to the VOB/C
The specification does not stand alone. What it does not say, the VOB/C says, in two directions.
| Classification | Status | Consequence for tendering |
|---|---|---|
| Incidental service | forms part of the contractual work even without mention in the text | need not be described, but must be priced by the tenderer |
| Additional service | does not form part of the contractual work unless agreed | must be tendered as a separate item |
Anyone unfamiliar with section 4 of the relevant ATV either tenders twice or omits items. The system is covered in the branch on the VOB/C.
Section 0 of the ATV acts likewise: it lists which particulars belong in the specification as the individual case requires. It is the tenderer's checklist and does not become part of the contract.
Why the effort pays
The relationship between quality of description and volume of variations is the economic core of this subject. It determines the moment at which a price is formed.
An item missing or unclearly described is not tendered, not priced and not ordered. It appears during construction as a variation, at a point when competition no longer exists.
A priority rule follows when checking a bill of quantities: completeness before accuracy. A slightly wrong quantity corrects itself through remeasurement; a missing item does not.
The system of variations is covered in the branch on the construction contract under VOB/B. It also sets out which kind of variation presupposes notice.
Data exchange
Bills of quantities are exchanged in structured form between the tendering party, the tenderers and the client. A standardised procedure with defined phases enables exchange between different software.
The practical benefit is that items, quantities and prices need not be re-entered and that tender checking can be automated. The article on GAEB data exchange covers the phases and their application.
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.