Changes to design, quantities and sequencing can alter both the price and the completion date. A sound variation claim connects the contractual instruction with the actual work, the pricing basis and the effect on the programme.
Establish what changed
Start with the original scope and the instruction history. A revised drawing may clarify an existing obligation or introduce a new one; the distinction matters. Identify the person authorised to instruct the change and preserve evidence of receipt. Different rules can apply under the BGB and an incorporated VOB/B contract.
Keep the BGB change procedure and valuation separate
Section 650b BGB provides a process aimed at agreement on a requested change and the resulting price. Where its requirements are met, an employer can issue an instruction in text form after the statutory negotiation period. The existence of an instruction does not establish the amount claimed.
For qualifying instructions, section 650c BGB addresses necessary costs and appropriate allowances. Its interim-payment mechanism is subject to conditions and later adjustment. It should not be treated as a general entitlement to 80% of every disputed invoice.
Build a claim that can be assessed
We structure the scope comparison, entitlement, quantity evidence, cost records and programme analysis. Separate direct work costs from disruption and delay claims. An agreed price for additional work may not resolve the time consequences unless the settlement says so.
Four practical examples
Illustrative scenarios: the appropriate steps depend on the contract, evidence and applicable law. These are not reports of client matters.
A stronger foundation
A revised structural design increases reinforcement. Compare the original design obligation with the new instruction and assemble quantities and procurement records.
A late tenant change
A tenant changes the fit-out after procurement. Record who instructed the change and separate replacement costs from avoidable expenditure.
Acceleration requested
The employer asks for weekend work after a design change. Define the acceleration measures, cost and intended programme benefit before mobilisation.
A disputed omission
Part of the work is removed. Check whether this is a variation, partial termination or transfer to another contractor before calculating the credit.
Documents that help us assess your position
The original scope, all revised drawings, instruction emails, quotations, cost records, daily reports and both baseline and updated programmes.
Discuss your project or dispute
Tell us where the project is located, who is involved and whether a deadline is approaching. We can then clarify the scope of the proposed engagement and the next steps.
Related construction law services
Legal framework & further reading
Reviewed: 12 November 2026. Statutory references are to German law unless stated otherwise.