Price revision under Breyne Law: rules to know

Price revision is one of the main sources of construction dispute. The Breyne Law does not prohibit it, but frames it — decoded.

1. The principle

A price revision clause is valid if:

• Indexed on a recognised official index (I-index, construction CCT materials index).
• Transparent application (explicit formula in the contract).
• Reasonable cap, without manifest excess.

Without these conditions, the clause may be declared void by the judge.

2. Common indices

• I-index: construction wage index published monthly.
• Materials index: material prices by category (concrete, steel, wood).
• CCT 124: construction collective agreement, wage base.

The contract must specify which index, which reference date and which formula.

3. Frequent abuses

• Unilateral indexation without justification → void.
• Unsuitable index (e.g. general inflation instead of construction index).
• Floating reference period at the developer’s choice.
• Retroactive revision on already-paid instalments.

The Mons 5 February 2022 ruling held that an excessive clause causes return to the initial price (see case law).

4. How to defend yourself

Demand costed detail of each revision: reference index, date, formula, calculation. If not communicated or abusive, contractor formal notice and reduction action.

Our Breyne Law advisory audits the clause and every revision — lasting protection.