The quote was agreed, the work is finished and then the final invoice arrives: a considerable amount higher than agreed, with "additional work" as the explanation. Sometimes rightly so, because halfway through you wanted an extra wall or a more expensive tap. Often not, because the contractor did work you never asked for, or never warned you that it would cost extra. On this point the law is clearer than many contractors and clients think. This article explains when additional work may be charged, how provisional sums and a contingency item work, how you record additional work in advance and what you do if an unexpected bill turns up anyway.
What additional work is and what it is not
Meerwerk (additional work) is work that falls outside the original assignment and for which the contractor asks for an extra payment. Its mirror image is minderwerk (reduced work): agreed work that is dropped and for which you get a deduction. At the heart of every dispute is the question of what exactly belonged to the original assignment. That is why the description of the work in the quote and the agreement is more important than the price underneath it. If it says "renovate bathroom as per drawing, including pipework, tiling and sanitary ware", then moving a drain that is shown on the drawing is not additional work. If it only says "renovate bathroom", the contractor has room to argue that moving pipes was not included.
In practice, three situations lead to additional work. First, changes at your request: an extra socket, a different type of tile, a wall that has to go after all. Second, unforeseen circumstances: a rotten floor joist under the bathroom, a foundation that lies differently than expected, material containing asbestos, a pipe in an unexpected place. Third, errors or gaps in the assignment: a drawing that is wrong, a forgotten item, a provisional sum that was underestimated. Each of these three has its own rules.
What the law says: article 7:755 and the duty to warn
The most important rule is in article 7:755 of the Burgerlijk Wetboek (BW, the Dutch Civil Code). If you as the client want additions or changes to the work, the contractor can only claim a price increase if they warned you in good time of the need for that price increase. There is one exception: if you should have understood that need yourself. An extra circuit in the meter cupboard comes with costs, everyone understands that; that a different type of tile requires a more expensive adhesive and more hours is not something a layperson needs to know. A contractor who carries out your change without warning and sends a bill afterwards is in a weak legal position.
In addition, three rules apply to the price itself. If a target price (richtprijs) was agreed instead of a fixed price, under article 7:752 it may not be exceeded by more than ten percent, unless the contractor warned you in such good time that you could still intervene, for example by limiting or simplifying the work. With a fixed price, the risk of setbacks lies in principle with the contractor; only in the case of cost-increasing circumstances that the contractor did not know about and did not need to know about can they ask for an adjustment under article 7:753, and even then only if they warned you as quickly as possible. Finally, article 7:754 obliges the contractor to warn you about errors in the assignment, faulty drawings or unsuitable materials that you supply yourself. Since the Wet kwaliteitsborging (Wkb, the Dutch Quality Assurance for Building Act), that warning must be written and unambiguous for building work, and the contractor must point out to you in good time the consequences for the work. More on this in The Quality Assurance Act: what does the Wkb mean for your renovation.
Two misunderstandings deserve attention. The law does not require a written warning for additional work at your request; a verbal remark counts, but is hard to prove afterwards. And not all rules carry the same weight. Article 7:755 and the stricter duty to warn in article 7:754 are mandatory law: they may not be deviated from to your disadvantage if you commission the work as a consumer. The rules on the target price and on cost-increasing circumstances (7:752 and 7:753) are default law, so trade-association terms or the contractor's own terms may deviate from them within the limits of consumer law. So always read what the terms and conditions say about additional work.
Provisional sums, fixed price, cost-plus work and the contingency item
How sensitive your renovation is to additional work depends on the pricing form in the quote. A fixed contract price gives the most certainty: everything in the description is included for that price, and setbacks within the assignment are for the contractor. A target price is an estimate with the statutory margin of ten percent. Work on a cost-plus basis (regie), where you pay for hours and materials, has no additional work but also no ceiling; in that case ask for a maximum budget and interim timesheets.
A stelpost (provisional sum) is an amount included in a fixed quote for an item that has not yet been chosen, for example the tiles or the sanitary ware. If you choose something more expensive, you pay the difference; if you choose something cheaper, you get it back. Provisional sums are the most common source of a higher final invoice, not because the contractor does anything wrong, but because they are often estimated low to keep the quote attractive. For each provisional sum, ask what the contractor has allowed and whether that is realistic for the quality you want. Also check whether the provisional sum covers only the material or the installation too; a more expensive tile can take more hours to lay.
A contingency item (post onvoorzien) is something else: a reserve, usually a percentage of the contract price, for surprises that nobody could foresee. Agree that this item is only drawn on with your written approval and that whatever is left over is not invoiced. You can read how to set these items side by side in different quotes in Comparing quotes: how to read a building quote.
How to avoid disputes: recording additional work
- Include an additional-work clause in the agreement. Agree that additional work is only carried out after your written approval of a statement with a description, price and consequences for the schedule. An email or a message via the platform is enough, as long as it can be found again.
- Use an additional-work form or a fixed message thread. For each change: what is changing, what does it cost extra or less, how many days does completion shift, who gave approval and when. Number the changes so that they are recognisable on the final invoice.
- Agree the rate for additional work in advance: the hourly rate, the mark-up on materials and how hours are recorded. Then any later discussion is only about the number of hours, not about the price per hour.
- Ask for a stop and a statement at every surprise. If the contractor finds a rotten joist, the right response is for them to halt the work at that point, inform you, state the solution and the price, and only continue after approval. That also gives you the chance to ask for a second opinion.
- Keep a log yourself with photos and dates. In a dispute about what was discussed when, whoever has the best records wins.
- Do not pay for additional work in advance or in cash, and link the payment to the completion of the relevant item.
On VerbouwPro, contact with the contractor or the carpenter runs through messages on the platform, so arrangements about changes are automatically recorded in writing and can be found again.
An unexpected invoice: what you may refuse and how to act
If you do receive a final invoice with additional work you do not recognise, work through it systematically. First ask for a breakdown per item: what was done, when, how many hours and materials, and who gave the instruction for it. Put it next to the agreement and your log and divide the items into three groups.
- Additional work at your request for which you were warned, or whose costs you should have understood: you pay for that, at a reasonable price or the rates agreed in advance.
- Additional work at your request without a warning that you did not need to foresee: under article 7:755 the contractor may not claim a price increase for it. You can refuse these items with reasons.
- Work you never asked for, including setbacks that fell within a fixed price or errors in the contractor's own workmanship: that is not additional work and you do not pay for it.
Pay the undisputed part of the invoice on time and explain in writing which items you dispute and why, with reference to the agreement and the law. That way you do not end up in default yourself and you keep the discussion clean. Do not refuse the whole invoice because of one disputed item; that can lead to interest and collection costs on the part you did owe. If the contractor threatens to stop work or refuse completion until you pay, that is generally not justified when your dispute is reasonably substantiated; record that in writing too.
If you cannot sort it out together, there are three routes. If the contractor is covered by trade-association terms with a disputes committee (geschillencommissie), that is the fastest and cheapest route, with a binding ruling. Otherwise you can go to the kantonrechter (sub-district court), where you can litigate without a lawyer up to a statutory limit; legal expenses insurance or the Juridisch Loket (free legal advice service) can help you get started. For a dispute linked to defects in the work, read in Handover of your renovation: checklist and your rights what you may withhold at completion and how to report defects. The best protection, however, remains a clear description of the work in advance, realistic provisional sums and a firm agreement that nothing extra is done without your written approval.