Model element quantities mapped to trade engines, with unmapped elements listed.
Costing and commercial control. 5 questions answered below, each with the arithmetic behind it and the limits of what the tool decides. Open the BIM and IFC Import tool.
An IFC file is a model exchanged between authoring tools, and it carries geometry, properties and a classification. This import reads the elements it recognises, maps them to the categories the calculators use, and hands the quantities to the deterministic engine rather than trusting the model's own totals. The mapping is where the work is. A wall in one tool is an IfcWall with a thickness and a height; in another it is an extrusion with a material layer set. Elements that cannot be mapped are reported rather than guessed at, and the quantities that come through are the ones the geometry supports: areas, volumes and lengths. A model with no material assignments produces geometry with no specification, and the tool says which of the two it is working from.
A model with two hundred walls, forty slabs and ninety openings maps to wall area, slab volume and an opening schedule. Twelve elements come back unmapped because they are modelled as generic extrusions with no classification, and four walls carry no material layer set so their thickness is geometric rather than specified. The takeoff shows two hundred walls with quantities and twelve elements with no category, which is a fixable model rather than a failed import.
It reads the file, recognises the element types it understands, maps them to the categories the calculators use, and extracts the quantities the geometry supports. Elements it cannot map are listed with their type rather than discarded. The output is a takeoff by element that can be traced back to the model, which is the point of importing rather than re measuring. On a coordinated model that saves a week; on an uncoordinated one it tells you what has to be fixed before it can be used at all.
They are listed as unmapped with their type, so the reason is visible. Usually it is a modelling decision: an element extruded as a generic form, a wall without a classification, a family that has no equivalent. Those are fixable in the authoring tool, and reporting them converts a silent gap in a takeoff into a task for the modeller.
No. The model's quantities are shown beside the extracted ones so a difference can be seen, but the takeoff is calculated from the geometry by the same engine as the standalone calculators. A model can carry a quantity that was typed rather than derived, and trusting it would import someone else's arithmetic error into an estimate that otherwise has none.
Wall areas and the thicknesses behind them, slab and footing volumes, roof areas at the modelled pitch, run lengths for pipe and conduit, and openings as a schedule with sizes. Those are the quantities the geometry supports reliably. Anything that depends on a specification, such as a block size or a mix, comes from the properties where they exist and is reported as missing where they do not.
No. Validation is a separate discipline: coordination, clashes, model completeness and standards compliance are checks against a brief, and a quantity import does none of them. What the import does is tell you which elements it could not use, which is a partial and useful signal about model quality rather than an assessment of it.