A scan-to-BIM model is usable when it passes three tests: the quantities come out right in two clicks (an area or wall schedule gives figures you can use as they are), the file structure is clean (correct element categories, consistent levels, parameters filled in), and the deviations between the model and the point cloud are measured and documented. The visual rendering is not one of the three tests: a model can be perfect in 3D view and useless for a quantity take-off, a building permit application or a renovation study.
This is a recurring debate among BIM modellers, and it touches a real problem in the market: most models are sold on screenshots, but used in spreadsheets. At Studio BIM we are a team of architects: we know what a fellow architect will do with the model on Monday morning. We model for the data, not for the rendering.
This article gives you the acceptance grid we apply to our own deliveries, and which you can apply to any model, including the ones you have already received.
The symptoms of a “pretty but dumb” model
You will spot them in ten minutes, without being a Revit or ArchiCAD expert:
- The wall schedule lists “Wall 1”, “Wall 12 copy 3”, “Basic Wall (2)”... Forty types for a building that really has eight. Any take-off by type becomes impossible.
- The parameters are empty. No material, no function (load-bearing or not), no phase. The model contains geometry, not information: the “I” in BIM has vanished.
- The areas do not add up. The sum of the rooms on a floor matches neither the floor area nor anything verifiable. Usually: forgotten rooms, overlapping zones, or areas measured against badly joined walls.
- Ultra-detailed manufacturer objects make the file crawl. A mixer tap downloaded from the manufacturer can weigh more than the entire structural shell. The file takes three minutes to open, the views stutter, nobody works in it.
- Elements modelled “as volumes”. A staircase made as a generic mass, a roof as a simple extrusion: it looks nice in 3D, but the element does not exist for schedules or for the IFC export.
- Everything is attached to the wrong level, or to a single one. Walls that run through three storeys, floors placed at arbitrary heights: filtering by storey no longer works.
- The IFC export comes out empty or wrong. The geometry arrives as “proxies” with no classes (IfcWall, IfcSlab...), or with holes. The model does not survive leaving its native software.
- No document comes with the model. No report, no stated tolerance, no list of unsurveyed zones. You do not know what was checked and what was assumed.
A single one of these symptoms is enough to turn a model that cost several thousand francs into a mere 3D image.
The 10-point acceptance checklist
To run through at delivery, before closing the contract. Allow half a day for an ordinary building. Points 1 to 4 are pass-or-fail.
1. Overlay the point cloud and probe the deviations. Demand the cloud along with the model (it is your data, you paid for it; see our model tender specification). Cut five to ten sections at places you choose, not the provider’s, and measure the wall-to-cloud deviation. It must stay within the contractual tolerance, commonly in the region of ±10 to ±25 mm depending on the agreed LOD.
2. Check that every element is in the right category. A wall is a Wall, a slab is a Slab, a staircase is a Stair, not generic volumes. Quick test: open a schedule by category; if whole parts of the building do not appear in it, they were modelled “outside” the system.
3. Open three elements at random and read their parameters. Properly named type, material, host level, phase. Fields that are systematically empty on a random sample will be empty everywhere.
4. Have the areas totalled. Generate the area table and set it against a reference: floor area measured on the cloud, an old dimensioned plan, the deed. If the contract provides for areas according to SIA 416, each value must be assigned to its category and the totals must reconcile floor by floor.
5. Check the levels. One level per real storey, heights consistent with each other, and every element attached to the right level. Isolate one storey: nothing from the others should remain visible.
6. Audit the file structure. Organised and named layers (ArchiCAD), consistent worksets (Revit), an identifiable template. A chaotic structure makes any rework of the file more expensive than the model itself.
7. Measure performance. Opening time, file size relative to the building’s floor area, smoothness of the views. In Revit, also look at the number of warnings: a few dozen can be justified; several hundred signal forced modelling.
8. Export an IFC and open it in a neutral viewer (BIMcollab ZOOM, Solibri Anywhere...). The classes must be correct, the geometry complete, the properties present. A model that does not survive IFC locks you in with one software vendor, and with one provider.
9. Check the georeferencing. Project base point, orientation to north, height: if the contract provides for positioning in national coordinates (MN95/LV95, LN02 heights), check it on two known points. A wrong base point is paid for when the cadastre or the engineer’s design is overlaid.
10. Demand the modelling report. Unscanned zones (inaccessible attic, locked room), assumptions made, deviations beyond tolerance and their justification (a genuinely out-of-plumb wall, for instance). A model without documented reservations is not a checked model: it is a model whose defects nobody has looked at.
This checklist applies to Revit and ArchiCAD alike; the checkpoints change name but not nature. On the choice of software itself, see our comparison Scan-to-BIM: Revit or ArchiCAD?.
How we check our models internally
At Studio BIM, every model is checked and validated before delivery by an architect from the studio other than the one who produced it. This second pair of eyes goes back through the checklist above, with three systematic passes:
- Cloud-to-model check on sections, across all storeys, before anything is sent;
- Data acceptance: schedules generated and reviewed (types, parameters, areas), IFC export opened in a neutral viewer;
- Delivery report listing the tolerance applied, unsurveyed zones and assumptions.
The fact that our modellers are architects is not a decorative argument: it is what makes it possible, in front of an ambiguous cloud, to decide between a lining, a duct and a load-bearing wall, and to model the element that will serve the project rather than the one that fills the 3D view. It is the heart of our modelling service.
Already have a doubtful model? Have it audited, free of charge
If you have received a model and doubt is setting in, start with three quick checks that need no full professional software: ask for the cloud and overlay three sections, generate a wall schedule, export an IFC into a free viewer. Twenty minutes is often enough to locate the problem.
Then, two cases. If the structure is sound but incomplete (parameters to fill in, types to rename), the model can be repaired: that is rework that can be priced. If the geometry is wrong or the structure chaotic, rework frequently costs more than remodelling on the existing cloud; you need to know that before committing hours.
Studio BIM carries out this audit free of charge and with no commitment: sample cloud-to-model check, structure and data audit, written report with a recommendation (repair or remodel). An architect’s view from outside the original contract, with measurements rather than impressions: you leave with a diagnosis, whatever you decide next.
FAQ
What tolerance should I demand between the cloud and the model? It is set in the contract, according to the LOD and the use: in the region of ±10 mm for a detailed construction model, ±20 to ±25 mm for an ordinary existing building intended for design studies. What matters is not the figure: it is that it is written down, measurable and verified by sampling at delivery.
Is the IFC file enough, without the native file? No. IFC is an exchange format, not a working format: to continue the design work you need the native file (RVT or PLN) in addition to the IFC. Demand both in the specification, along with the point cloud.
How long does a model acceptance take? Half a day for an ordinary building, following the 10 points above. That is little compared with the cost of the model, and with the cost of the decisions that will rest on it.
Can I demand the point cloud along with the model? Yes, and you should: without the cloud, you simply cannot check the geometry. Ownership of the delivered data (cloud, native file, IFC) is settled in the specification, before the order.
A model that works for you
A scan-to-BIM model is judged on its data: correct quantities in two clicks, clean structure, documented deviations. The rendering follows, never the other way round.
Do you have a building to survey and model? Configure your project and get a price in 2 minutes on our quote configurator. And if you are preparing a tender, our model tender specification already includes these acceptance criteria.