Two design stages instead of three
The Italian public contracts code enacted by Legislative Decree 36 of 2023 reduced the number of design stages from three to two. The intermediate stage, the progetto definitivo, was abolished, and the sequence now runs from the progetto di fattibilità tecnica ed economica, the technical and economic feasibility design, to the progetto esecutivo, the detailed design.
The simplification did not lighten the workload. Design obligations previously spread across three steps now sit on two, and the detailed design absorbs part of the detail that used to mature gradually.
The effect on cost estimating is direct. The bill of quantities accompanying the detailed design must be complete and final, because there is no longer an intermediate stage in which to correct roughly estimated quantities along the way. The feasibility design already contains an economic assessment, but with a different level of development and a programming rather than an accounting purpose.
The documents that accompany the bill of quantities
Article 22 of Annex I.7 to the code lists the documents making up the detailed design. The bill of quantities appears alongside the quadro economico, the overall cost framework of the project, and next to it sit deliverables that directly condition its content.
| Deliverable | Relationship with the bill of quantities |
|---|---|
| Drawings | Source of the quantities. Every item must be traceable back to a drawing |
| Elenco dei prezzi unitari and price analyses | Holds the unit rates applied to the quantities and the analyses for items absent from the price books |
| Capitolato speciale d'appalto | Sets the technical requirements and execution methods that justify each item |
| Labour incidence schedule | Derives from the bill and makes the labour component embedded in the rates legible |
| Cronoprogramma | Places the measured works in sequence and supports the forecast of interim valuations |
| Maintenance plan | Revisits the measured works from an asset management perspective |
| Health and safety plan | Determines the oneri della sicurezza, safety costs, which receive separate treatment in the bill |
This documentary architecture explains why the bill of quantities cannot be produced in isolation, nor deferred to a stage after design. It is a synthesis deliverable that translates choices already made elsewhere into quantities and value.
Who prepares it and with what responsibility
Preparation falls to the designer, who is answerable for consistency between the bill and the other deliverables. In public works the detailed design undergoes prior verification, and the check covers the correspondence between measured quantities and graphic representations as well as the correct application of rates. The check lists used by contracting authorities for this purpose devote a dedicated section to the bill of quantities and the cost framework.
Responsibility does not end at tender stage. A bill that understates quantities generates variations, requests for new rates and disputes during construction, with consequences that fall on the designer before they fall on the contractor.
The contractual value of the document
This is one of the more delicate points of the regime. Article 18 of the code provides that the bill of quantities forms an integral part of the contract where it is referred to in the tender notice or the invitation to tender. Article 31 of Annex I.7, however, requires the bill to be attached to the draft contract as a document of the detailed design. Reading the two provisions together has fuelled a technical and legal debate that cannot be regarded as settled.
In practice the question resolves itself by looking at how the consideration is determined. Under an appalto a misura, a measured contract, the quantities actually executed are valued by applying the unit rates, and the bill retains an operational role throughout the works. Under an appalto a corpo, a lump sum contract, the consideration is fixed and the bill serves mainly to build the contract amount and to apportion work stage percentages for the purposes of interim payments.
The bill of quantities in private work
In the private sector there is no statutory obligation to prepare a bill of quantities, and the decision rests with the parties. Its usefulness is unchanged, however. Without a bill, one contractor's quotation cannot be compared with another's, variations have no objective reference point and the client has no instrument for tracking expenditure. In professional practice the bill remains the tool through which the architect or engineer keeps the budget of a private project governable, with one substantive difference: the contract price arises from agreement between the parties, not from the mandatory application of a price book.
Where to go deeper
The pages that follow cover the operational detail of preparation, the distinction between the unpriced and priced bill of quantities, and the rules by which works are measured. They also carry the measurement rules by category.
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.