CAD-to-BIM and Scan-to-BIM are two approaches to creating BIM models of existing buildings. They differ in source data, accuracy, and cost.
CAD-to-BIM (Drawing-Based)
CAD-to-BIM starts with existing 2D CAD drawings (DWG/DXF files) and converts them into a 3D BIM model. A modeler traces over the 2D plans, elevations, and sections to create 3D parametric objects in Revit or ArchiCAD.
Advantages:
- Lower cost if accurate drawings already exist
- Faster turnaround for simple buildings
- No on-site visit required
Disadvantages:
- Relies on drawings that may be outdated, incomplete, or inaccurate
- Cannot capture as-built deviations (walls that are not plumb, floors that are not level)
- Missing information must be filled in with assumptions
- No field verification of actual conditions
Scan-to-BIM (Reality-Based)
Scan-to-BIM starts with 3D laser scan data (point clouds) captured on-site. A modeler traces over the point cloud to create BIM objects that match actual, measured conditions.
Advantages:
- Captures actual existing conditions with ±2-4mm accuracy
- Reveals hidden conditions (structural deflection, MEP routing)
- No reliance on potentially outdated drawings
- Enables clash detection between existing and proposed systems
Disadvantages:
- Higher upfront cost (scanning + modeling vs. modeling only)
- Requires site access for scanning
- Longer timeline (scanning phase + modeling phase)
When to Use Each
| Scenario | Recommended Approach |
|---|---|
| Recent construction with accurate as-built drawings | CAD-to-BIM |
| Renovation of existing building (any age) | Scan-to-BIM |
| Building with known drawing discrepancies | Scan-to-BIM |
| Complex MEP documentation needed | Scan-to-BIM |
| Budget-constrained, simple geometry | CAD-to-BIM |
| Legal or insurance documentation | Scan-to-BIM |
Cost Comparison
- CAD-to-BIM: Typically $0.08-$0.25/sqft (modeling only)
- Scan-to-BIM: $0.20-$0.70/sqft (scanning) + $0.15-$0.75/sqft (modeling)
The higher cost of Scan-to-BIM is offset by reduced rework, fewer change orders, and confidence that the model represents reality.
THE FUTURE 3D provides the scanning component — delivering survey-grade point clouds that your team or BIM provider converts into accurate BIM models.