The former approach: carrying forward the original calculation
For decades, carrying forward the original calculation was the governing route. The new price was derived from the figures in the tender: labour, materials, plant, overheads, risk and profit were taken from the Urkalkulation, the tender build-up, and applied to the changed work.
The rule of thumb held that a good price stayed a good price and a bad one stayed bad. It had a certain logic: a contractor who priced tightly to win the work should not improve their margin afterwards through variations.
That approach presupposed disclosure of the tender build-up. This is why many tender documents to this day require it to be lodged with the tender, although its function has since shifted.
What the case law changed
The Federal Court of Justice abandoned that approach in 2019 for quantities above 110 per cent. The decision expressly covered that case alone.
What governs since are the actually necessary costs plus appropriate mark-ups, not the carried-forward figures of the tender build-up. The calculation thereby detaches from the tender and turns to the execution.
The reasoning lies in the wording of the provision, which speaks of a new price taking account of the increased or reduced costs. Increased costs are actual costs, not calculated allowances.
The open area. Whether the same principles apply to changed and additional work has not been decided by the Federal Court of Justice. The prevailing view affirms it, because the wording of the relevant provisions coincides, and the lower courts have followed. Certainty at the highest level does not exist.
In practice that means an uncomfortable but honest starting position: the governing method of calculation for the commonest kind of variation is not conclusively settled. Anyone committing to one method should be able to compute the other in the alternative.
What actually necessary costs are
The term requires its own exercise and is more demanding than carrying figures forward. Five components have to be established separately.
| Component | How established |
|---|---|
| Labour | actual input times actual average rate |
| Materials | actual procurement prices for the changed work |
| Plant | actual standing time and use |
| Subcontract work | actual quoted prices |
| Mark-ups | appropriate, for site overheads, general administration, risk and profit |
Two points here are contested or require interpretation. Both concern open-ended terms the provision does not define itself.
Necessary does not mean arbitrary. What governs are the costs arising under efficient operation, not those actually incurred where they were avoidable.
Appropriate does not mean customary. Which mark-ups are appropriate must be justified case by case. Falling back on the percentages in the tender build-up is an obvious and frequently chosen route, but it is not compulsory.
What follows for both sides
The change acts in both directions and alters the negotiating position. Neither side gains throughout.
| Side | What changes |
|---|---|
| For the contractor | a contractor who tendered below cost is no longer tied to that low level; that devalues the speculative strategy in one respect and opens it in another |
| For the client | a properly costed variation price may exceed what carrying forward would have produced; the former assurance that a low tender level also caps variations is gone |
| For both | the effort of pricing rises: costs must be established, evidenced and, in a dispute, assessed by experts |
A recommendation follows that sidesteps the legal question and is almost always right economically: a variation agreement before execution is cheaper than the dispute afterwards, whatever price is agreed. It spares both sides the task of proving actually necessary costs.
What the tender build-up still achieves
Lodging the tender build-up has not become superfluous despite the change in case law. Its function has shifted from the basis of calculation to evidence.
| Function today | What it serves |
|---|---|
| It evidences the pricing structure | percentages for site overheads and general administration can be derived from it and support the justification of appropriate mark-ups |
| It reveals loaded rates | conspicuous shifts between items become visible before they take effect in variations |
| It supports delimitation | below the 10 per cent threshold the original unit rate continues to govern, and the build-up evidences its composition |
For tender documents this means lodging it remains sensible, but its function has shifted from the basis of calculation to evidence and a control quantity. Its absence today chiefly hampers the justification of the mark-ups.
What belongs in a variation
Five components make a variation verifiable and therefore enforceable. The fifth is missing most often and costs the most.
- The occasion, referring to the order or the triggering circumstance.
- The delimitation from the contractual work, that is what is to be executed additionally or differently.
- The cost calculation, broken down by labour, materials, plant and subcontract work.
- The mark-ups, with reasons for their appropriateness.
- The effect on the construction periods, since a change regularly touches the programme.
The fifth is most often omitted and the most expensive. An unclaimed extension of time can lead to delay, and the consequences of delay routinely exceed the variation sum.
The conditions of the claim are covered in the article on variations under § 2 VOB/B. It also sets out which notice requirements the claim presupposes.
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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.