What Is VDC?

The visible deliverable is often a clash report and a meeting. The useful deliverable is a closed decision: this duct drops below the beam, this sleeve is added, this wall moves two inches, recorded on a drawing or a model the authors will update. A report with hundreds of clashes and no owner for each one is not VDC. It is a list.

Other products include quantity checks against the estimate, a 4D sequence that ties activities to model elements, and site logistics for crane or laydown constraints. Each of those needs a model reliable enough for that use. A coordination model and a quantity model may be the same file used with different rules, or they may not.

On design-bid-build jobs the design team authors the models and the contractor may build a coordination model during construction, especially for MEP. On design-build and CM-at-risk jobs the builder is in the room earlier, which is when VDC can still change the documents instead of only documenting clashes. The contract should say who updates the model after a coordination decision.

The architect and engineers of record remain responsible for the design they seal. A VDC meeting does not transfer that responsibility to the coordinator who found the clash. Someone with the right license has to revise the document. VDC makes the conflict visible. It does not seal the fix.

Virtual construction of a pour sequence needs elements that exist and are located well enough to order. If the structural model is still generic framing, a day-by-day 4D simulation is fiction. Level of development is the agreement about reliability. VDC plans should cite it. "We have a model" is not a plan.

Trade models from detailers, produced for fabrication, are often more reliable for coordination than the design model. They also arrive later. The VDC schedule has to say which model is the one the meeting will trust this month.

Coordination meetings put the mechanical, electrical, plumbing, fire protection, and structural authors in one place with a federated view. The coordinator screens clashes before the meeting so the hour is spent on the ones that need a design choice. Assigning a clash to "team" with no date is how the same clash returns for six weeks.

Decisions need a place to live outside the meeting recording: a revised sheet, an ASI or RFI if the contract requires it, or an updated model element. If the only record is the screenshot in the slide deck, the field will build the old drawing.