As-built model after completion: what contracting authorities require

With the final acceptance of works funded by the PNRR (Italy's National Recovery and Resilience Plan) and the first contracts subject to the BIM mandate of art. 43 of Legislative Decree 36/2023, many contractors reach the end of the works with a specific request from the contracting authority: hand over the as-built model, the model of the asset as it was actually built. Handover is often a condition of the final interim valuation, and the construction model has not always been kept up to date during the works.

Where the requirement is written

In the exchange information requirements (EIR, called capitolato informativo in Italian public tenders), which are part of the tender documents: they set out the model uses, the level of development of the objects, the formats and the delivery dates. The contractor responded with the pre-appointment BIM execution plan and, after the award, with the BIM execution plan, which sets out how and when the as-built model will be delivered. The contract and the programme also matter, when they tie the delivery of the models to a payment.

The first step, before even opening the model, is to reread these documents and list what is actually required: disciplines, objects, data, formats and delivery rules.

What it usually contains

• The model for each discipline (architecture, structures, building services, external works) representing the asset as built, with objects at level of development LOD F of UNI 11337-4 where the requirements call for it.
• The data of the installed components: manufacturer, model, serial number where needed, location by room or by system, linked maintenance documents.
• The as-built drawings taken from the model, not drawn separately.
• The formats: native files and IFC with the required property sets; for operation, sometimes a COBie spreadsheet as well.
• The comparison report between design and construction, with tolerances, areas checked and remaining deviations.

Delivery normally takes place in the common data environment (CDE) specified by the contracting authority, following the naming, status and revision rules set out in the requirements.

How it is checked

Acceptance checks are the contracting authority's responsibility and usually cover three aspects: whether the model matches the asset, whether the required data are complete and whether the delivery rules are met. The contractor is better off running the same checks first: a verification survey by the appointed surveyor, with laser scanning in the building services and structural areas, a comparison between point cloud and model, and model checking against the rules in the requirements, such as names, classification and completed properties.

If the construction model was not kept up to date

This happens on contracts started before the BIM mandate or when the model stopped at the detailed design. The as-built model is then rebuilt from the finished asset: the appointed surveyor carries out the laser scan survey of the visible parts, the survey data are turned into a BIM model through scan to BIM, and the parts of the design model that changed are updated. For the parts no longer visible, such as concealed services, cable ducts and underground utilities, the construction records count: dated photos, site reports, supplier data sheets and certificates, measurements taken during installation.

The work can be organised in batches, so the first parts of the asset are delivered while the others are still in progress. Timescales depend on the size of the asset, the disciplines required and how well the construction was documented.

What slows handover down

Three situations come up again and again: the design model handed over under a new name, without the variations; component data collected at the end of the works, when the suppliers have already closed their files; IFC exported without checking that the required property sets came through. In all three cases the contracting authority asks for additions and handover slips.

The remedy is the same: decide at the start of the works who updates the model, how often and with which documents, and collect the suppliers' data while the components are being installed.

How we work

B1P Group supports contractors with the as-built model: updating the construction model during the works, BIM modelling from the appointed surveyor's survey data when the model is missing, completing the data required by the exchange information requirements, pre-handover model checking and delivery in native format and IFC. For anyone starting a BIM contract now, BIM for construction avoids reaching the end of the works with a model to rebuild.