The three elements
The provision requires the work 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. Four separate requirements follow from that single sentence.
| Element | Requirement | Test question |
|---|---|---|
| Clearly | only one reading possible | Could a tenderer read the text differently |
| Exhaustively | nothing material missing | Is a particular affecting price absent |
| In the same sense | comparability of tenders | Do differing readings produce differing prices |
| Without extensive preliminary work | the tenderer need not establish it themselves | Must the tenderer measure or survey themselves |
The last row is most often overlooked. The tenderer owes the pricing, not the establishment of its basis. A description forcing them to take measurements, survey the existing fabric or establish quantities themselves does not satisfy the principle.
The provision additionally requires that all circumstances influencing pricing be established and stated in the tender documents. That is an obligation on the client to investigate, not merely to disclose.
Who bears the risk of a gap
Here lies the practical core, supplemented by the prohibition on unusual risk. The two provisions interlock.
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 wording thus names two features that must be present together.
The two elements are cumulative. A risk the tenderer can influence may be assigned to them. So may a risk whose effect they can estimate. Only where both are absent does the prohibition apply.
An allocation of risk by knowledge and influence follows. It assigns each risk to the side able to steer or quantify it.
| Risk | Assignment |
|---|---|
| Construction method and work planning | contractor, they control it |
| Material price movement within normal bounds | contractor, they can estimate it |
| Ground conditions, so far as the client can establish them | client, they have the access |
| Condition of the existing fabric | client, they are the owner |
| Exceptional price movements | an unusual risk in the individual case |
The last row has been considered in case law: price increases arising from external events have been treated as an unusual risk. The classification depends on the individual case and should be assessed legally.
Wordings that breach the principle
Certain clauses recur in bills of quantities and are open to challenge. All four pursue the same aim, namely shifting a risk without describing it.
| Clause | Why it is open to challenge |
|---|---|
| Blanket references to the existing fabric | the tenderer is to form their own view and price all consequences; that shifts the client's duty to establish the facts |
| Completeness clauses | the unit rates are to cover even undescribed work; that circumvents the principle directly |
| Open quantity risk | quantities described merely as approximate where no measurement has been carried out |
| Unquantified difficulties | references to occupied premises, restricted working hours or access limitations without particulars enabling pricing |
The practical effect of such clauses is regularly the opposite of what was intended: they produce either risk premiums costing the client more than a sound specification, or they are ineffective and change nothing. Either way the client pays for a transfer of risk they do not obtain.
How to recognise a gap
Four checks reveal most specification defects at little cost in time. The last is the most effective, because it changes the perspective.
| Check | What it reveals |
|---|---|
| Against section 0 of the ATV | it lists which particulars belong in the specification; what appears there and is missing from the bill is a gap |
| Of the item types | provisional items and a high proportion of daywork are symptoms of incomplete design, not its solution |
| Of the units of measurement | does the unit correspond to the rule of the relevant ATV, or was it chosen for convenience |
| Reading it back as a tenderer | can every item be priced without a query, on a basis that appears in the text |
The structure of the bill of quantities is covered in the separate article. It also sets out which item types the VOB/A recognises at all.
The link to variations
The principle and the law of variations connect directly, and the connection is economically the most important in this subject. It determines the moment at which a price is formed.
Work not described in the contract but required to achieve the agreed result is additional work. It is paid under the rules of construction contract law, at a point when competition no longer exists.
A calculation follows that almost always favours the client: the effort of a complete specification is less than the price of the variations it prevents. The system of variations is covered in the article on § 2 VOB/B.
For the designer a second level arises. Completeness of the specification is a basic service, and its defects may be attributed to them.
What applies in existing buildings
In existing buildings the principle meets a structural difficulty. Part of the circumstances demonstrably cannot be known before the fabric is opened up, even with careful preparation.
The answer lies not in a blanket transfer of risk but in three measures. All three take effect before the tender goes out.
| Measure | Effect |
|---|---|
| Condition survey before tendering | what can be established by opening up elements should be established and stated |
| Stating the state of knowledge | named uncertainty can be priced; concealed uncertainty cannot |
| Contractual regulation of the procedure | how unforeseen circumstances are handled belongs agreed before they arise |
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.