Issue one specification to every bidder
Give each business the same drawings, product requirements, measured quantities and access conditions. Separate product supply, installation, protection, waste and checks. Identify work by location rather than asking for an undefined “complete renovation”. State which owner-supplied products are available and who takes responsibility for fitting them.
Use a clarification list with the offer revision and date. The consumer commissioning guidance recommends comparing detailed services and materials. Ask a bidder to confirm an exclusion rather than filling a blank with a zero. “By others” means you still need a responsible supplier and an amount in the full budget.
Understand the actual price agreement
An Angebot can contain a fixed package, unit prices with later measurement or expressly provisional items. A Kostenvoranschlag estimates cost; it is not automatically a price guarantee. Read scope, validity, quantity basis and accepted conditions together. A signed order for a later agreed change to the specification does not preserve the original scope merely because the first page says Festpreis.
Under BGB section 632(3), an estimate is not remunerated in case of doubt; clarify any agreed fee first. A separately commissioned survey or design service has its own scope and payment terms. Ask what you may use from that service if you choose a different construction business.
Normalise the offers before ranking them
| Item | Offer A | Offer B |
|---|---|---|
| Headline work offer | 21 000 | 18 500 |
| Missing protection, separately confirmed | 0 | 800 |
| Missing disposal, separately confirmed | 0 | 700 |
| Missing substrate work, separately confirmed | 0 | 1 500 |
| Comparable defined work | 21 000 | 21 500 |
| 19% VAT on comparable work | 3 990 | 4 085 |
| Comparable gross work | 24 990 | 25 585 |
| Common owner product supply gross | 5 950 | 5 950 |
| Defined work and purchases gross | 30 940 | 31 535 |
A includes the three named services in its EUR 21,000 headline. B initially looks EUR 2,500 cheaper, but the equivalent package is EUR 500 net or EUR 595 gross dearer. That does not settle business quality, programme or risk. It shows why ranking unadjusted totals can reverse the financial conclusion.
Check units, final totals and assumptions
For a measured unit-price item, establish whether 80 m² is actual laying area or simply the apartment’s floor area. If measured laying falls from 80 to 72 m² at a hypothetical EUR 45/m² net and the contract uses actual quantities, the net difference is EUR 360; gross difference EUR 428.40. A fixed package may work differently. Do not silently remeasure a genuinely agreed lump sum as though it were a unit-price contract.
Check applicable VAT and the final payable amount for each business. Match units such as m², running metre, item and hour; define whether hourly rates include one person or a crew and whether travel is extra. Ask how uncertain substrate repairs are measured and authorised. A low unit price does not make an unlimited quantity harmless.
Arrange what happens when the estimate changes
BGB section 649 requires prompt notice when a substantial overrun of the relevant non-guaranteed estimate is expected. It does not grant a universal percentage that can be spent without discussion. Ask for the reason, affected quantities, revised final amount and effect on time. Preserve evidence and seek advice before making a disputed termination decision.
For changed work, record the requested result, revised scope and agreed gross price before execution where possible. Construction-contract change rules may apply to a particular contract; “only written extras are ever payable” is too absolute. Separate a new owner choice from work required to deliver the already promised result, and have disagreements assessed rather than automatically paying both.
Select a complete and manageable offer
- Resolve missing services and product boundaries.
- Confirm the price basis and what will be measured again.
- Record gross totals and open allowances.
- Agree access, dates, checks and responsibility for interfaces.
- Set understandable payment evidence and a change process.
- Keep the accepted revision with later instructions.
Compare the final offers in Reno Pro using the same stage structure. Keep quality, documents and programme beside the price assessment. The purpose is to choose an offer you can understand and administer, with a full funding plan beyond the construction package.
Sources, date and scope
- Bundesministerium der Justiz / Bundesamt für Justiz — BGB — §§ 631–632, 633–637, 649, 650b–650g
- Bundesministerium der Justiz / Bundesamt für Justiz — BGB § 649 — Kostenanschlag
- Verbraucherzentrale — Handwerker: Auftrag, Abnahme und Rechnung
- Bundesministerium der Justiz / Bundesamt für Justiz — UStG § 12 — Steuersätze
Checked on 19 October 2026. Local examples concern Berlin unless stated otherwise. Check state law, heritage protection, community rules and actual work for the specific project. Teaching figures are invented euro amounts, not market prices or offers. The article projects are independent. Tax and funding calculations apply only under the stated assumptions; competent professionals resolve project-specific technical and legal questions.