Finding the right contractor often determines whether a building project succeeds or fails. Most mistakes happen before work begins: during selection, comparison and contract signing. These seven mistakes regularly cost project owners dearly.
Key points at a glance
- 53 % of project owners do not obtain comparison quotes — even though prices between quotes can differ by 20 to 30 % (LBS Research, 2025)
- 62 % choose their contractor primarily on price — 40 % later report serious problems
- Verbal agreements, excessive advance payments and missing contract clauses are the most common causes of disputes and additional costs
Mistake 1: deciding solely on price
The cheapest provider is rarely the best. A low total price can mean items are missing, quality standards are set low or the contractor has planned to charge for missing work as variations.
Instead: Compare unit rates rather than total prices. Check that all quotes cover the same scope. The cheapest complete quote is better than the cheapest incomplete one.
According to a survey by the Zentralverband des Deutschen Handwerks, 62 per cent of private clients choose their contractor primarily on price.1 At the same time, 40 per cent report problems during or after construction. The connection is no coincidence.
Mistake 2: not obtaining references
A professional website says little about work quality. Review platforms are helpful but insufficient because reviews can be manipulated.
Instead:
- Ask for 2 to 3 reference projects similar to yours
- Call previous clients and ask about punctuality, cleanliness and handling of additional charges
- Ask whether you can visit a completed project
- Check registration in the crafts register (Chamber of Crafts)
Mistake 3: verbal agreements instead of a written contract
"We'll do that as well" or "Of course that's included" are worthless phrases on site. What is not in the contract does not legally exist.
Instead: Record every agreement in writing, including variations, changes and promises. An email is sufficient as evidence. This is standard practice, not a sign of distrust.
Mistake 4: excessive advance payment
Some contractors demand 30, 40 or even 50 per cent upfront before starting work. This is not standard industry practice and carries a substantial risk: if the business becomes insolvent or work does not begin, your money is gone.
Instead:
- No advance payment above 10 to 20 per cent of the contract value
- Link stage payments to verifiable progress (e.g. 30 % after first fix, 30 % after surface finishes, 35 % after acceptance, 5 % retention)
- Final payment only after formal acceptance
Mistake 5: not having a quote reviewed
Most project owners sign a quote as soon as the price seems acceptable. They do not check the small print, missing items or whether individual prices are in line with the market.
Instead: Have the quote reviewed before signing, at least for contracts over 10,000 euros. A review costs from 79 euros and regularly identifies problems worth many times the review fee.
| Provider | Cost | Time |
|---|---|---|
| Surveyor | 360 to 714 € | 2 to 4 weeks |
| Consumer advice centre | 180 to 370 € | 1 to 3 weeks |
| VPB | 175 €+/hour | By arrangement |
| Cleverbauen24 (Basic) | 79 € | 3 to 4 working days |
| Cleverbauen24 (Express) | 99 € | 24 hours |
Mistake 6: not taking acceptance seriously
Acceptance is the most important point in the entire construction project. It reverses the burden of proof: before acceptance, the contractor must prove that their work is free of defects. Afterwards, you must prove that a defect exists.2
Instead:
- Never accept implicitly (so do not simply pay the final invoice)
- Written acceptance record with a list of defects
- Record all visible defects
- If unsure, involve a surveyor at acceptance
- Only carry out acceptance inspections in daylight (surfaces, joints, paintwork)
Mistake 7: not documenting defect liability in writing
Many project owners do not know how long their defect liability period lasts or when it began. If a defect appears after three years, it is unclear whether claims still exist.
Instead:
- Record the defect liability period in the contract (at least 5 years under BGB)
- Document the acceptance date (the period runs from this day)
- Report defects immediately in writing (by registered post or email with a read receipt)
- Enter defect liability deadlines in your calendar (reminder 3 months before expiry)
Checklist: recognising a good contractor
| Feature | Good sign | Warning sign |
|---|---|---|
| Quote | Detailed, with individual prices | Lump sum, without a breakdown |
| References | Offered proactively | Evasive answers |
| Schedule | Realistic programme | "We start tomorrow" (without planning) |
| Advance payment | Max. 10 to 20 % | 40 to 50 % before work starts |
| Communication | Contactable, responds promptly | Never contactable, verbal communication only |
| Defect liability | Clear contractual provision | Not discussed or addressed |
| Chamber of Crafts | Registered, verifiable | No information |
Frequently asked questions about finding contractors
How do I find a good contractor?
Recommendations from neighbours, friends or colleagues are the most reliable route. Also use Chamber of Crafts searches, trade platforms (MyHammer, Blauarbeit) and local trade guilds. Always obtain at least three quotes and request references.
How many quotes should I obtain?
At least three, ideally based on the same bill of quantities. That lets you compare like with like. For projects over 50,000 euros, five quotes are recommended.
How do I recognise an unreliable contractor?
Warning signs: a large advance payment before work starts, exclusively verbal agreements, unwillingness to break down individual prices, pressure to sign quickly and no verifiable Chamber of Crafts registration.
What should I do if a contractor delivers poor work?
Report defects immediately in writing and set a reasonable rectification deadline (usually 2 to 4 weeks). If the contractor fails to rectify them, you have the right to arrange rectification yourself (a replacement contractor at the original contractor's expense) or reduce the payment (§ 637 BGB).
Further guides
- Reviewing a construction quote – 7-point checklist and review options compared
- 7 warning signs of overpriced quotes – How to recognise overpriced contractors' quotes
- Negotiating a contractor's quote – 8 tips for fair prices
- Acceptance checklist – Step by step through acceptance
Sources
- Zentralverband des Deutschen Handwerks (ZDH): survey on contractor selection by private clients, 2024.
- BGB § 640: acceptance and reversal of the burden of proof in contracts for work.
- Verbraucherzentrale Bundesverband (vzbv): building, housing and energy guide – tips on selecting contractors and drafting contracts.
- Federal Ministry for Housing, Urban Development and Building (BMWSB): information for private project owners – contract law and defect rights.
- LBS Research: home purchase and project owner behaviour study 2025 – quote gathering and price comparison by private project owners.
Comments
Unfortunately, I made the mistake of trusting the first contractor I found because the reviews on a portal looked good. Portal reviews are very easy to influence.
Recommendations from people you know are worth their weight in gold. But what do you do when you are new to a city and do not know anyone?
Good point! If you do not have a personal network, I recommend first using the Chamber of Crafts search (at least for guild members), and second actively asking to visit reference projects — seeing completed projects in person. And third: ask about comparable projects in your area during the initial conversation.
I can only underline the point about allowing too little time to obtain quotes. People who put you under pressure usually don't want you to look closely.
Very practical article. Point 4 (no interim payments without proof of progress) particularly struck a chord — I must insist on that for my next project.