Avoiding additional charges – the project owner's guide

Variation costs are additional payment demands made by contractors or construction companies after the contract is signed. The best way to avoid them is to review the quote thoroughly before signing — unclear work descriptions, quantity reservations and missing boundaries between trades are the most common triggers. According to an analysis by FAU Erlangen and Almondia, 72 per cent of all private homes cost more than originally planned;¹ variations are one of the biggest cost drivers.

Key points at a glance

• 72 % of all private homes cost more than planned — variations are a major reason ([FAU Erlangen / Almondia](https://www.almondia.de/ratgeber/hausbau-teurer-als-geplant), 2017)
• The 7 most common traps: lump-sum items with actual-work clauses, unclear boundaries between trades, quantity reservations, contingent items, uncapped hourly work, excessive site setup and missing warranty clauses
• VOB/B § 2 Abs. 3 provides for a price adjustment when quantities vary by more than 10 % — on a 200 m² façade, this can quickly amount to several thousand euros
• You may reject additional charges if the work was already included in the contract — always request a written variation quote

Why do variations arise in the first place?

In its information for private project owners, the Federal Ministry for Housing, Urban Development and Building (BMWSB) states that a precise specification is the most effective protection against unexpected additional demands.² Not every variation is deliberate, however. The four most common causes:

1. Incomplete specification: If the exact work is not clearly defined, there is room for additional demands. A classic example: “painting as agreed” instead of a specific list of areas, coats and preparation work.
2. Deliberately underpriced items: Some companies deliberately set individual quantities or unit prices low to look cheaper when quotes are compared. They then recover the difference through variations.
3. Missing boundaries between trades: If responsibility for ancillary work such as protection, disposal or scaffolding is not defined, these costs appear later as additional charges.
4. Changes requested by the project owner: Changing materials, adjusting layouts or ordering extra work during construction means expecting variations. This is legitimate — but clear rules are needed on how changes are commissioned and billed.

According to a Building Owners' Protection Association (BSB) survey, over 70 per cent of building quotes submitted by its members contain at least one item with an increased variation risk.³ In severe cases, variations can reach 20 to 30 per cent of the original contract value — up to 30.000 euros extra on a 100.000-euro contract.

The 7 most common variation traps in building quotes

These seven patterns occur particularly often in practice. Each can cost several hundred to several thousand euros.

1. Lump-sum items with “actual work” clauses

A lump-sum item initially sounds convenient: a fixed price for a specific service. Problems arise when the same item contains phrases such as “additional work charged at actual cost” or “deviations billed by the hour”. The lump sum then becomes a minimum price with an open upper limit rather than a true fixed price.

What you can do: Check every lump-sum item to see whether it really covers everything. Obtain written confirmation that the lump sum includes all work necessary for full completion.

2. Unclear scope boundaries

During renovations, several trades often work at the same time. If the painter's quote says “substrate must be handed over swept clean” but the dry liner's quote says nothing about cleaning, you end up paying twice. Typical disputes concern covering and protection, site cleaning, old material disposal and scaffolding provision.

What you can do: Ask each trade to state clearly which ancillary services are included in the price. Record responsibility for shared tasks such as scaffolding, site electricity and disposal in a separate document.

3. Quantity reservation clauses

Phrases such as “approximate quantities, billed according to actual site measurement” mean that the quoted quantities are not binding. VOB/B § 2 Abs. 3 provides for an adjustment to remuneration when quantities vary by more than 10 per cent.⁴ On a WDVS façade, this can quickly make a difference of several thousand euros if 220 m² is suddenly billed instead of the estimated 180 m².

What you can do: Have quantities checked before awarding the contract. Agree a maximum deviation beyond which renegotiation takes place. If the company cannot provide specific site measurements, that is a warning sign — more in our article on common warning signs of overpriced quotes.

4. Unnecessary contingent items

Contingent items are services called on only if needed. This makes sense where there is genuine uncertainty — such as whether timber panelling lies beneath old plaster. Problems arise when a quote contains numerous contingent items that are highly likely to be needed. This depresses the visible quote price while the actual cost is higher.

What you can do: Go through every contingent item individually. Is it realistic that this work will not be needed? If a contingent item is almost certain to be necessary during normal construction, it should be included in the quote as a regular item.

5. Uncapped hourly work

Almost every building quote contains an item for daywork or hourly work. Without a cap, substantial costs can accumulate. An hourly rate of 55 euros net sounds moderate, but 40 hours of daywork quickly comes to 2.200 euros net plus materials.

What you can do: Agree a cap on hourly work — for example, a maximum of 20 hours or 1.500 euros. Above that, the company should submit a separate variation for your approval before carrying out the work. Have hourly work signed off daily.

6. Excessive site setup costs

Site setup includes everything needed before the actual work begins: placing containers, connecting site electricity and putting protective measures in place. Some quotes allocate 10 to 15 per cent of the contract value without breaking down the individual items. On an 80.000-euro contract, 15 per cent for site setup would be a hefty 12.000 euros.

What you can do: Ask for an itemised breakdown of site setup costs. For renovations to existing buildings, 3 to 5 per cent is normal; new builds with complex logistics may be somewhat higher. Question anything above 8 per cent.

7. Missing warranty clauses

Not a variation in the classic sense, but a substantial cost risk: if the quote lacks adequate warranty provisions, you pay for remedial work yourself. Under § 634a BGB, the warranty period for buildings is five years; under VOB/B § 13, four years.⁵ Some companies try to shorten these periods in the small print. Shortened warranty periods may be invalid in consumer contracts under § 309 Nr. 8b BGB.⁶

What you can do: Make sure the contract explicitly states a warranty period of at least four years, preferably five years under BGB. More in our Guide to construction defect liability.

Preventing additional charges: your checklist

According to the BMWSB guide for private project owners, most unexpected additional demands can be avoided through a structured quote review before signing the contract.² Work through these eight points — each can save you several hundred to several thousand euros:

1. Check the specification for completeness: Are all work stages described specifically? Is preparation such as removal, priming or disposal missing?
2. Check quantities: Do the square metre and linear metre figures match your plans? If in doubt, commission an independent measurement.
3. Question lump-sum items: What exactly does the lump sum include? Are there clauses that undermine the fixed price?
4. Assess contingent items realistically: Which are likely to be needed? Add them to the quoted total to establish the realistic overall price. Our guide Lump-sum price vs unit price helps you assess the options.
5. Cap hourly work: Agree a maximum and an approval process for exceeding it.
6. Clarify ancillary work: Who supplies scaffolding? Who disposes of old materials? Who pays for site electricity? These points belong in the quote in writing.
7. Ensure warranty protection: At least four years under VOB/B, preferably five years under BGB. Does this also cover subcontractors?
8. Agree rules for variations: Specify that variations may only be carried out after prior written approval. Always request a variation quote with a price breakdown.

What should you do when a variation arrives?

Even good preparation cannot rule out every variation. In its guide to contractor invoices, the consumer advice centre recommends requesting every variation in writing before payment and comparing it with the original contract — because the claimed additional work often turns out to be part of the agreed scope already.⁷

Step 1: Do not sign immediately. Many project owners give in to pressure because work would otherwise stop. A reputable company gives you time to review the variation. Request the variation quote in writing.

Step 2: Check entitlement. Is the additional work genuinely absent from the original quote? Go through the specification item by item.

Step 3: Compare prices. Even if the variation is justified, the prices must be reasonable. Compare the unit prices charged with those in the original quote. For a WDVS façade, the variation's square metre price should not suddenly be 30 per cent above the contract price.

Step 4: Negotiate in writing. Document everything. Record what additional work will be done, at what price and by when. Verbal agreements on site regularly lead to disputes.

Step 5: Get professional support. For variations above 2.000 euros, involving an independent expert is worthwhile. The cost is small compared with an unjustified variation you accept through lack of knowledge.

Frequently asked questions about additional charges

Must I accept every variation?

No. You are only obliged to pay for variations that were genuinely outside the original scope and that you commissioned. If a service belongs to the agreed scope under the specification, the company cannot charge for it as a variation. Request every variation in writing and compare it with the contract before agreeing.

What is the maximum allowed for additional charges?

There is no statutory upper limit. Under § 650c BGB, remuneration for changes ordered by the client is based on the actual necessary costs plus reasonable mark-ups.⁸ In practice, a variation must not be substantially more expensive than the same work was priced in the original quote.

Can I deduct additional charges from tax?

Under § 35a EStG, tax relief can be claimed on 20 per cent of labour costs for contractors' services in an owner-occupied property, up to 1.200 euros per year. This also applies to variations, provided the costs are for labour rather than materials. Requirements: an invoice showing labour separately and payment by bank transfer.

Does a VOB contract protect against variations better than a BGB contract?

Not necessarily. VOB/B contains more detailed rules on variations (§ 2 Abs. 5 and 6 VOB/B),⁹ but these apply only if VOB/B has been validly incorporated into the contract. According to BSB, effective incorporation into consumer contracts often fails because of formal errors.³ The best protection is a complete specification and clear variation rules rather than the form of contract.

For more on what matters when reading a building quote overall, see our Guide: reviewing a construction quote. Typical warning signs of inflated prices are explained in Warning signs: identifying inflated prices. If you have several quotes, you will find a structured comparison method in Comparing contractor quotes properly . Current market prices for typical renovation trades are shown in Renovation costs 2026.

Sources

1. Almondia / FAU Erlangen — housebuilding more expensive than planned: analysis of 3.000 construction projects, 2017
2. BMWSB — information and tips for private project owners
3. BSB, Building Owners' Protection Association — construction contract guide: variations and incorporation of VOB/B
4. VOB/B § 2 Abs. 3 — remuneration for quantity changes (gesetze-im-internet.de)
5. § 634a BGB — limitation periods for defect claims (gesetze-im-internet.de)
6. § 309 Nr. 8b BGB — prohibited warranty-period clauses in consumer contracts
7. Consumer advice centre — reviewing contractor invoices and paying correctly
8. § 650c BGB — remuneration adjustments for changes ordered by the client
9. VOB/B § 2 Abs. 5 and 6 — variation rules for changes ordered by the client
10. Federation of German Consumer Organisations (vzbv) — building, housing and energy: consumer rights under contracts for work, variation law and cost control