The unilateral power to order changes
Every variation starts from a peculiarity of the construction contract. The client can order changes unilaterally, without the contractor's consent.
| Basis | Subject |
|---|---|
| § 1 para. 3 VOB/B | ordering changes to the design remains reserved to the client |
| § 1 para. 4 sentence 1 VOB/B | additional work becoming necessary for execution |
A comparable power exists under the statutory construction contract law for contracts concluded since the beginning of 2018. A contract without the VOB/B therefore knows the same right.
The power is what keeps a project workable: a design unchanged over years is the exception. It has a reverse side, and that concerns price.
The consequences for payment
Where the client orders a change, a claim to adjust the price follows. The VOB/B distinguishes by trigger.
| Case | Basis | Trigger |
|---|---|---|
| Quantity variation above 10 per cent | § 2 para. 3 | departure from the quantity without any order |
| Changed work | § 2 para. 5 | the client's order |
| Additional work | § 2 para. 6 | work not provided for in the contract |
The first row differs fundamentally from the other two: it presupposes no order. Where the actual quantity of an item departs from the one tendered, the claim arises from the remeasurement contract model itself.
The system in detail is covered in the article on variations under § 2 VOB/B. It also sets out which case presupposes notice.
Case law has altered how variations are priced
For decades a rule of thumb governed the pricing of variations, resting on carrying forward the original calculation. A good price stayed a good price, a bad one stayed bad.
The Federal Court of Justice abandoned that rule in 2019 for excess quantities. What governs since is not the carried-forward figures of the original calculation but the actually necessary costs plus appropriate mark-ups, which have to be established separately.
The economic effect is substantial and runs both ways. A contractor who tendered below cost is no longer tied to that level. One who tendered soundly can no longer carry their original margin into variations.
Whether the same principles apply to changed and additional work has not been decided by the Federal Court of Justice. The prevailing view and the lower courts assume so, because the wording of the relevant provisions coincides. Legal certainty does not exist on the point.
Measurement and the final account
The VOB/B governs how completed work is established and invoiced. Two principles shape the area.
| Principle | Content | Legal effect |
|---|---|---|
| Joint measurement | the work is established jointly by both sides so far as possible | considerable evidential weight; its omission works against whoever later relies on different quantities |
| The verifiable invoice | the final account must be capable of being followed | a condition of falling due, not of the amount of the claim |
How measurement proceeds sits not in the VOB/B but in the VOB/C. The article on measurement and the final account covers the interplay.
Handover
Handover is the pivotal moment of the construction contract. It triggers several consequences at once.
| Effect | Significance |
|---|---|
| Payment falls due | together with the verifiable final account |
| Limitation periods begin | for defect claims |
| Risk passes | to the client |
| Burden of proof reverses | for defects, onto the client |
The last row matters most in practice: before handover the contractor must prove the absence of defects; after it, the client must prove the defect. The article on handover covers the forms and their conditions.
The further areas
Three areas complete the picture and bear indirectly on cost. They act not on the price but on its enforceability.
| Area | What to watch |
|---|---|
| Construction periods and hindrance | where execution is delayed for reasons within the client's responsibility, claims arise; notice of hindrance is regularly a condition |
| Defect claims | the VOB/B provides limitation periods differing from the statutory ones; which applies turns on valid incorporation |
| Termination | both sides may terminate under certain conditions; settling a terminated contract follows its own rules |
What this means for cost planning
The link between contract drafting and cost certainty comes down to three propositions. The third is the only one both sides can act on directly.
| Proposition | What follows |
|---|---|
| The power to order changes makes cost certainty a question of description | so long as the client may change things, the completeness of the specification decides how often they must |
| Pricing variations has become less predictable | moving away from carrying the original calculation forward widens the range of possible prices, since the actually necessary costs must first be established |
| Documentation determines enforceability | order, notice, joint measurement and a verifiable account are formal requirements whose neglect devalues claims that exist on the merits |
The link to the specification is covered in the branch on the specification under the VOB/A. It also sets out how an incomplete specification can be recognised.
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.