Construction and engineering / 02
BIM modeling for contractors
A model is worth having when it answers a question the drawings cannot: where the duct hits the beam, what the quantity really is, how the phases sequence. Built for that, not for a rendering.
Built from the same documents as the estimate
The model and the takeoff come from one reading of one set. That is the point of doing both under one roof: the quantity in the workbook and the quantity in the model are the same quantity, derived once, and a change to the set changes both.
That also sets the limit. A model is only as resolved as the documents it is built from. Where a set is at design development the model says so in its level of development, and it does not invent the detail the engineer has not yet drawn.
What gets built
- Discipline models in Revit
- Architectural, structural and MEP built to the level of development the use requires and stated, from LOD 200 for quantity and massing to LOD 350 for coordination.
- Model based quantities
- Schedules pulled from the model and reconciled to the measured takeoff, with the differences explained rather than averaged. Two independent quantities that agree are worth more than either alone.
- Coordination and clash review
- Discipline models federated and checked where systems compete for the same space: ceiling voids, shafts, the structure that duct and pipe have to cross. Reported as a list a contractor can act on, not a count.
- Phasing and sequencing views
- The model cut by phase, for a bid that has to demonstrate how an occupied building stays occupied.
Documents needed
- The full issued set, all disciplines
- The specification, for the level of development required
- Existing model files where the design team will release them
- Survey or point cloud data where existing conditions matter
Questions contractors ask
Do we get the model file?
Yes, the native Revit file and an IFC export, with the level of development stated on each element category.
Can the model replace the takeoff?
It can produce quantities, and they are reconciled to the measured takeoff. Using both is what gives you a checkable number. Using either alone is a single opinion.
Is this a delivered service or an offer?
An offer, at this point. The estimating and drawing work is where the delivered history sits. If a model is the main thing you need, say so and we will tell you honestly whether we are the right firm for it.
Send the set. Get a fee back.
A written fee and a delivery date come back before anything is measured.