The Index for updating material assets in construction (IM) aims at enabling the updating of the value of property in the absence of an available replacement value in the calculation of the equipment charges. It allows to update the material values for used equipment quotations, park valuations, especially for expertise in disaster.

It should not be confused with the Various indices for construction - MATP - Equipment item for civil engineering indices - Base 2010), whose purpose is escalating contracts.

An order of the Ministry of Public Works and Transport dated 12 December 1959 approved the "Blue Scale", especially a first IM index formula for the calculation of employment costs of major civil engineering equipments. At this time, this index entered in the formulas for enhancing public works markets. Changes in formula and / or base took place in 1969, 1973, 1977 and 1986, with an initial reference to 1.

The following documents are used for sequencing the history of this index:

• The information published on the index IM in 1986 by Le Moniteur des Travaux publics;

• The introduction to the method of determining employment expenses in 1986 FNTP manual;

• An extract of the scale of the FNTP for determining employment costs of major civil engineering materials, the 01/10/1969 (p 7 and 8.);

• Excerpts of the Annals of FNTP as of 1960, 1969 and 1974.

The IM index was very close in concept (cost index) and its sources (public statistics indices) to the various construction indices, responsibility of which was transferred to INSEE in 2014. FNTP, formerly associated with the Ministry of Ecology, Sustainable Development and Energy for the calculation and validation of TP indices and some various construction indices, wished at that time that INSEE also resumes the calculation of the IM index.

Computation of BT/TP and production cost indexes in construction