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Most of what's built is designed in detail, made and installed by specialist subcontractors: the trades. Steel fabricators, façade specialists, MEP contractors, lift companies, joiners. On many projects they take the design models and develop them into fabrication models, and their information is what the building is actually made from.
| Trade | What they model | What it's used for |
|---|---|---|
| Steel fabricator | Connections, plates, bolts | Shop drawings, CNC fabrication |
| MEP contractor | Spools, supports, fittings | Prefabrication, installation |
| Façade specialist | Panels, brackets, joints | Panel fabrication, installation sequence |
| Lift company | Shafts, machinery, loads | Builders' work, coordination |
Working with trades
- Agree the handover point: which design model the trade starts from and when ownership passes.
- Bring their models back into the federation: fabrication detail can clash with other trades.
- Approve before fabrication: once parts are made, changes are expensive.
- Collect product data as they go: manufacturer, model, serial, warranty, maintenance.
The MEP contractor prefabricates pipework spools from its own fabrication model, which is never federated. On site, a third of the spools clash with the sprinkler contractor's mains, modelled separately. The spools are cut and re-welded on site, and the benefit of prefabrication is lost.
Every trade's fabrication model joins the weekly federation for the area being fabricated. MEP and sprinkler clashes are resolved in the models; the spools are approved, fabricated and installed without rework.
The façade specialist is appointed at stage 4. Write four things to agree with them about information.
Key takeaways
- Specialist subcontractors (trades) design in detail, fabricate and install their packages.
- Many produce fabrication models (steel connections, MEP spools, façade panels) from the design models.
- Their models must come back into the federation for coordination before fabrication.
- Their product data is the most important source of handover information.