The price list for building materials, the Mercuriale, is a well-known document in Belgium. The price list is considered a price monitoring system. Based on multiple categories of building materials, the price evolution is displayed using indices.

The index plays a very important role when making both an initial calculation and a recalculation. Particularly in public tenders, it is very common to invoke a price revision clause in construction contracts based on price developments.

As part of the reform process, Mercuriale introduced a new index in January 2021: ‘Index I 2021’. Index I 2021 is composed of 60 products and is grouped into 11 categories. The calculation of the “updated Index” starts with the sales prices of November 2020, and therefore uses November 2020 = 100 as the base.

Contracting parties must rely on Index I 2021 when:

It concerns public tenders that started before 2023 and continue into 2023
The standard I-index of the materials was already applied
As of January 2023, a combined index of I and I-2021 is required to calculate the revision coefficient.

Specifications may provide for various types of price revision formulas. A commonly used formula is:

p = P * [ x 1 * (s / S) + x 2 * ( i / I ) + (1 – x 1 – x 2 ) ]
Where X 1 and X 2 correspond to the weighting coefficients (x1 for wages = values ​​S) (x2 for materials) included in the specifications.

« p » = the revised price.
« P » = the original price.
« s » = the value of index S at the time of the revision.
« S » = the value of index S at the time of signing the contract.
« i » = the value of index I at the time of the revision.
« I » = the value of index I at the time of signing the contract.

Want to know more about the application of Index I 2021 in the KPD ecosystem?