Construction cost index (ICC) 2026: complete guide

Updated April 4, 2026 - The construction cost index (ICC — indice du cout de la construction) remains a useful reference in certain leases, indexation clauses and real estate analyses. At Q4 2025, the latest INSEE publication (released March 24, 2026) places the ICC at 111.0 in base 100 in 2021, down 2.37 % year-on-year compared to Q4 2024 (113.7). This movement fits into a broader context of slowing construction costs, which the production cost index (ICP-F) confirms with a moderate increase of +1.6 % year-on-year in the same quarter.

To go further, also see Real estate situation, Do you have to open an SCI to invest? and Family SARL or SCI.

The ICC is a quarterly index published by INSEE that measures the evolution of costs borne by project owners in the new housing construction sector. It covers expenditure on materials, labour, transport and general costs related to construction.

The reference base is 100 in 2021 (annual average). The index is calculated for metropolitan France and is revised quarterly. It is distinct from two other indices published in the same series:

• ▸the ICP-F (production cost index in construction), which covers the entire construction sector and stood at 115.0 in Q4 2025;
• ▸the IPEA (price index for maintenance and improvement works), which tracks renovation prices and stood at 118.5 (provisional data) in Q4 2025.

Each index serves a specific purpose. Confusing them in a contractual clause can make a revision inapplicable or contestable.

Here are the latest values published by INSEE on March 24, 2026:

(p: provisional data — Source: INSEE, 24/03/2026)

Several insights emerge from these figures:

The ICC is down 2.37 % year-on-year between Q4 2024 and Q4 2025. This decrease reflects a slowdown in material costs and a moderation of wholesale price pressures in the building sector.

The ICC peaked in Q1 2025 (115.8) before gradually declining. Q4 2025 (111.0) represents the lowest level since Q3 2023 (113.6), signalling a significant easing of construction costs.

The ICP-F remains on an upward trend (+1.6 % year-on-year in Q4 2025), meaning that overall production costs are still rising, albeit at a moderate pace. The ICC, more focused on new housing, benefits from a more favourable dynamic.

The IPEA rose 1.2 % year-on-year in Q4 2025. Renovation and improvement works therefore remain more expensive than new construction in relative terms — a trend that directly impacts property rehabilitation budgets.

The ICC retains several practical uses, even though its scope of application has narrowed over the years:

Indexation of commercial leases and older contracts

Certain commercial leases and construction contracts concluded before the introduction of the commercial rent index (ILC) or the tertiary activities rent index (ILAT) still reference the ICC. When the contractual clause explicitly designates the ICC, that is the index that must be applied, even if other indices are more recent or more specific.

Price revision in construction contracts

Public works contracts and individual house construction contracts (CCMI) may include price revision clauses based on the ICC. These clauses allow the contract price to be adjusted according to the evolution of costs observed between signing and execution of the works.

Economic monitoring and real estate analysis

For real estate professionals, developers and investors, the ICC serves as a trend indicator on the evolution of construction costs. It helps anticipate margins, calibrate forecast budgets and compare cost evolution with selling price trends.

Comparison with other real estate indices

The ICC compares usefully with the IRL (rent reference index), ILC, ILAT and IPEA. These comparisons help substantiate valuation reasoning, rent revision or contractual negotiation.

The revision formula is generally provided for in the contract. In its most common form, it reads:

New amount = Initial amount x (Reference index / Base index)

Where:

• ▸the reference index is the latest index known at the revision date;
• ▸the base index is the index used at the time of contract signing or the last revision.

Concrete example: a commercial lease signed in Q1 2024 provides for an annual revision based on the ICC. The initial rent is EUR 10,000. The ICC in Q1 2024 was 115.8. The ICC in Q4 2025 (latest available index) is 111.0.

The revised rent would be: 10,000 x (111.0 / 115.8) = EUR 9,585.49.

In this case, the decline in the ICC results in a rent reduction. This is a rare but possible situation when the reference index is lower than the base index.

If the contract includes a floor or ceiling clause, the revision may be capped. Check whether the clause allows for a decrease or only provides for increases (asymmetric clause).

• ▸Verify the exact index specified in the contract: do not substitute one index for another without an addendum. If the contract mentions the ICC, use the ICC, not the ICP-F or IPEA.
• ▸Use the correct publication date: INSEE publishes indices with a one-quarter lag. As of April 4, 2026, the latest available index is Q4 2025 (published March 24, 2026).
• ▸Respect the revision frequency: most clauses provide for annual revision. Do not revise more frequently than stipulated.
• ▸Document the calculation applied: keep a written record of the calculation, with references to the indices used and publication dates.
• ▸Do not automatically replace ICC with ILC or ILAT: these indices have different fields of application. Changing the index requires a contract addendum.

Hayot Expertise insight: an indexation file is first secured by rereading the clause. Choosing the wrong index creates more risk than the calculation itself. In practice, we find that index errors are the leading cause of disputes during audits or litigation.

The choice of index depends on the nature of the contract and the purpose of the revision:

The ICC is the only index that recorded a decline year-on-year in Q4 2025. This particularity can have a significant impact on contracts that reference it, especially in a context where other indices remain on an upward trend.

Using the wrong index or applying an incorrect formula exposes you to several risks:

• ▸Challenge by the tenant or counterparty: a revision based on an index not provided for in the contract can be annulled by a judge.
• ▸Retroactive adjustment: if the error is discovered after several years, amounts unduly received or not received must be regularised.
• ▸Loss of trust: repeated indexation errors damage the contractual relationship and can complicate future negotiations.
• ▸Penalties for unfair clauses: certain asymmetric indexation clauses (providing only for increases) have been deemed unfair by case law.

We can help you review the contract, the target index and the chosen revision method. Our support covers clause analysis, revision calculation and preparation of notification letters.

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At Q4 2025, the construction cost index stands at 111.0 (base 100 in 2021), down 2.37 % year-on-year. This evolution contrasts with the moderate rise in the ICP-F (+1.6 %) and the IPEA (+1.2 %). The ICC must be used with precision: right index, right period, right clause. In a context of easing construction costs, contracts that reference the ICC may see their amounts revised downward — a situation that deserves particular attention during annual revisions.

Need to check an indexation calculation or a sensitive real estate file? We can assist you with analysing your clauses and calculating your revisions.

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(Official sources: INSEE — Construction cost and price indices, publication of 24/03/2026 for Q4 2025, https://www.insee.fr/fr/statistiques/2015347)

What is the latest known value of the ICC in 2026?

As of April 4, 2026, the latest value published by INSEE is for Q4 2025, at 111.0 in base 100 in 2021. This data was released on March 24, 2026. The ICC is down 2.37 % compared to Q4 2024 (113.7). The next index (Q1 2026) will be published by INSEE around late June 2026.

What is the difference between ICC, ICP-F and IPEA?

These three indices are published by INSEE but measure different realities. The ICC (construction cost index) tracks new housing construction costs in metropolitan France. The ICP-F (production cost index) covers the entire construction sector in France. The IPEA (maintenance and improvement price index) tracks renovation prices. In Q4 2025, the ICC is the only one in decline (-2.37 %), while the ICP-F rose +1.6 % and the IPEA +1.2 %.

Can you use a different index than the one specified in the contract?

No. The revision index is a contractual element. If the lease or contract designates the ICC, you cannot unilaterally replace it with the ILC, ILAT or any other index. Changing the index requires an addendum signed by both parties. Using an unlisted index exposes you to revision annulment and retroactive adjustment.

How is a rent revision calculated using the ICC?

The formula is: New rent = Initial rent x (Reference index / Base index). The reference index is the latest known index at the revision date, and the base index is the one used at signing or the last revision. If the reference index is lower than the base index, the rent may decrease, unless the contract provides for a floor clause.

Is the ICC still used for recent commercial leases?

Increasingly less so. Commercial leases concluded since 2007 generally reference the ILC (commercial rent index) or the ILAT (tertiary activities rent index). The ICC is still used, however, in certain older contracts, CCMI (individual house construction contracts) and some works contracts. Always check the indexation clause of each contract to identify the applicable index.