The regulatory context
The Italian public contracts code provides for the adoption of digital information management methods and tools for the design and delivery of projects above a given value threshold, with effect from 1 January 2025 for works exceeding one million euros. The detailed arrangements are set out in the dedicated annex.
To this is added the capitolato informativo, the employer's information requirements document, introduced into Annex I.7 by Legislative Decree 209 of 2024. It defines the general and specific information requirements needed for digital management of the project, and therefore establishes the level of detail and reliability at which quantities must be extractable from the model.
That second point is what directly concerns whoever prepares the bill. A model developed without explicit information requirements on quantities produces an extraction that is formally correct and unusable.
What the model returns and what it does not
| Category | Extractable from the model | To be added manually |
|---|---|---|
| Structure | Concrete volumes, reinforcement weights where modelled, formwork areas | Complex formwork, staged pours, temporary works |
| Envelope and partitions | Areas and volumes of the elements | Treatment of surrounds, junctions, unmodelled elements |
| Finishes | Areas by type | Extras for work to small areas and at height |
| Services | Network lengths, number of fittings and terminals | Supports, penetrations, notional network allowances in outlet point bases |
| Excavation and earthworks | Geometric volumes | Actual versus theoretical section, operational widening |
| Site charges | Nothing | Scaffolding, protection, handling, safety charges |
The last row matters most. A model describes the finished works, not the process delivering them, and items tied to the process remain entirely to be built. On a refurbishment project the share of the bill not derivable from the model can be substantial.
The critical point: matching objects to items
Extracting quantities is not the difficult step. The difficult step is matching the objects in the model to the items in the prezzario, and the reason is that the two systems classify reality differently.
The model groups by construction element. The prezzario groups by operation. A wall modelled as a single object corresponds to several prezzario items, from the masonry to plaster on two faces to decoration, and each of those items has its own measurement basis.
This is where the principal risk sits. The area the model returns is the geometric area of the element. The quantity the prezzario requires may be one measured on a different convention, with deductions for openings, dimensional thresholds and extras for working the surrounds. Applying the geometric figure without checking the basis produces a systematic divergence across the whole category.
Managing the gap
Three measures substantially reduce the risk. They concern modelling, coding and checking.
The first is defining the correspondence between objects and items before modelling rather than after. If the structure of the model is conceived for extraction, the correspondence becomes a stable table; if it is conceived only for representation, every extraction requires manual reconciliation.
The second is checking the prezzario measurement basis for the categories with the greatest incidence, and adjusting the extraction accordingly. The critical categories are always the same: plaster and finishes for deductions, excavation for the reference section, services for the choice between length and outlet point.
The third is recording the provenance of every quantity, distinguishing those extracted from those added manually. That is the information needed when the model is updated: the former regenerate, the latter have to be reviewed.
The link with the construction stage
Where digital information management tools are used, the works supervisor ensures the correlation between the accounting records and the information models produced or updated during construction. The correlation must be set up before work starts.
A demand for structural consistency follows that concerns whoever prepares the bill. If the accounts will correlate to the model, the structure of the items and their correspondence with the parts of the works must be settled once and settled stably, because every divergence between the structure of the bill and that of the accounts is paid for at every interim valuation.
Note: the legislative references in this page relate to Italy and are current as at the date of publication. Public procurement rules change frequently, and the version in force should be checked before any operational use.