Ordering changes under section 650b BGB without losing the budget

Section 650b(1) BGB distinguishes two cases, and the difference has a direct effect on price and obligations. No. 1 covers "a change to the agreed result of the work (section 631(2))" (unofficial translation, as are all quotations here), that is, a change to what is to be built. No. 2 covers "a change necessary to achieve the agreed result of the work", that is, a change without which the agreed result would not be achieved.

Under no. 1, reasonableness is part of the contractor's defence. If the contractor relies on internal operational reasons for unreasonableness, it bears the burden of proof. For the client this means that a desired change cannot be forced at will, whereas a necessary one can.

Under no. 2, responsibility for design decides the cost. Under s. 650c(1) BGB, there is no claim to extra pay for a necessary change if the contractor also owes the design of the building. A client building with a contractor that does its own design has built-in protection in these cases; a client who supplies the design bears the cost of its gaps.

The law first requires an attempt at agreement. The parties "shall seek [...] agreement on the change" and on the extra or reduced pay. The contractor must make an offer for the extra or reduced pay. Where the client is responsible for the design, the offer is only owed once the client has supplied the design required.

Only after 30 days may the client order the change. Section 650b(2) BGB: "If, within 30 days of receipt of the change request by the contractor, the parties do not reach agreement under subsection 1, the client may order the change in text form." The contractor is then obliged to comply with the order, in the case of no. 1 only if it is reasonable.

The 30 days are a budget question, not a formality. A client who requests a change late must choose between waiting 30 days while the site carries on and seeking agreement under time pressure. Foreseeable changes therefore belong on the table as early as possible, together with the design they require.

Text form means documented, not oral. A change order given at a site meeting and appearing only in the minutes is a risk for both sides. A separate, numbered change order referring to the change request and the offer is the clean solution.

Extra pay is calculated on actual costs, not on the offer. Section 650c(1) BGB: pay for the increased or reduced effort is to be determined "on the basis of the costs actually required, with reasonable mark-ups for general overheads, risk and profit". For the budget, this means the final amount is often known only after the work is done.

The Urkalkulation (original costing) is the client's most important lever, and it must be pulled at signature. Under s. 650c(2) BGB, the contractor can calculate the extra pay on the basis of an original costing deposited as agreed. The pay updated in this way is presumed to correspond to pay under subsection 1; the presumption is rebuttable. A client who agrees in the contract that the original costing is deposited creates a traceable price basis for every later change. A client who forgoes it negotiates every change on actual costs it does not know.

Reduced costs are part of the same mechanism. A change order can also reduce or replace work. Omitted work that is not deducted is a hidden variation; it belongs in the register with the same weight as a claim for extra pay.

Without agreement on the amount, the contractor can bill part of it in advance. Under s. 650c(3) BGB, when calculating interim payments the contractor can apply "80 per cent of an extra pay stated in an offer" under s. 650b(1) sentence 2, if the parties have not agreed on the amount or no court decision provides otherwise. The extra pay calculated under subsections 1 and 2 then only falls due after Abnahme (acceptance of the work). Payments exceeding the extra pay owed must be repaid with interest.

For the client, this rule has two separate effects. On liquidity: 80 per cent of a high offer flows out immediately, even if the client considers the amount excessive. On the forecast: the line does not carry the interim payment but the probable final amount. An inflated offer is therefore not only a negotiating issue but a liquidity issue, and it is worth assessing it promptly and in writing.

A fictitious example for orientation. A contractor offers EUR 50,000 net for a change that has been ordered; the client considers EUR 35,000 appropriate. Without agreement, the contractor can include EUR 40,000 (80 per cent of 50,000) in its interim invoice. If the amount owed later turns out to be EUR 35,000, EUR 5,000 must be repaid with interest. From the outset, the forecast shows the amount the client considers probable, and the liquidity plan shows the EUR 40,000.

The law makes interim relief easier. For disputes over the right to order changes or the adjustment of pay, "after construction has begun it is not necessary to show grounds for the interim injunction". Both sides can therefore obtain an einstweilige Verfügung (interim injunction) more easily. For the budget, this is above all a reason to document the client's own assessment of every disputed variation so that it can be produced at short notice.

The right to order changes also applies against the designer, with its own pay rule. Under s. 650q(1) BGB, s. 650b and ss. 650e to 650h apply accordingly to architects' and engineers' contracts, unless this subtitle provides otherwise. Under subsection 2, the adjustment of pay after change orders follows the fee calculation rules of the HOAI where the services fall within its scope; otherwise s. 650c applies accordingly.

Every building change can therefore trigger two invoices: the contractor's variation and the fee adjustment of the designer who designs the change. Both belong in the forecast. Whether a change also affects a public law permit is a question of public building law, which is to be kept separate from private construction contract law.

Under a VOB/B contract, separate change rules sit alongside the BGB. Section 1(3) VOB/B: "The client reserves the right to order changes to the building design." Section 1(4) covers work not agreed but required. Pay follows s. 2(5) and (6) VOB/B; it is covered in the article on variations under section 2 VOB/B.

How these rules relate to ss. 650b and 650c BGB has not been conclusively settled. A published decision of the LG Hechingen (Regional Court, 02.11.2021, 2 O 305/21, NJW-Spezial 2022, 110) held s. 1(3) and (4) VOB/B invalid where the VOB/B is not agreed as a whole, and gave precedence to ss. 650b and 650c BGB. No BGH decision on this question appears in the sources reviewed here. This is a single published decision, not a settled rule. What incorporation "as a whole" means is explained in the article on agreeing the VOB/B. Practical consequence for the budget: a client who agrees the VOB/B with departures should not assume that the VOB/B change rules will hold, and should keep the s. 650b BGB procedure in mind as a fallback.

The right to order changes protects the budget only as far as the contract prepares for it. Five provisions prepare for it:

The last line is the most important. A change order is a spending decision. It belongs to whoever answers for the budget, not to whoever happens to be on site. How ordered changes are then tracked in the budget is shown in the article on the variation register. If a change becomes so large that termination looks cheaper, that is a separate calculation: it is set out in the article on terminating the construction contract.