As-built modeling accuracy is one of the most critical success factors in Scan to BIM projects. When working with laser-scanned data, defining clear modeling tolerances ensures that the expectations between the clients, designers, contractors and BIM teams remain aligned across different Levels of Development (LOD). From early design intent to the fabrication-ready models, tolerances play a vital role in determining how closely a BIM model represents the existing site conditions.
This blog explains how modeling tolerances should be defined and applied across LOD 200 to LOD 500 in Scan to BIM deliverables.
What Are Modeling Tolerances in Scan to BIM?
Modeling tolerance refers to the acceptable deviation between the modeled BIM elements and the original point cloud data captured on site. Since point clouds contain millions of data points with varying accuracy levels, every Scan to BIM project requires predefined tolerances to avoid over-modeling or misinterpretation of scan data.
Clear tolerance definitions helps to:
- Maintain consistency across disciplines
- Control modeling time and cost
- Make sure the model serves its intended purpose.
Factors That Influence Tolerance Definition
Before assigning tolerances, it is necessary to evaluate:
- Scan accuracy and resolution (equipment type and site conditions)
- Project objectives (design validation, renovation, clash detection or fabrication)
- Stakeholder usage (architectural design, MEP coordination, construction)
- Required LOD for each building element
These factors directly impact how tightly the model should follow the point cloud.
Modeling Tolerances by LOD Level
1) LOD 200 – Conceptual Representation
At LOD 200, the focus is on approximate geometry and spatial relationships rather than the exact dimensions.
- Elements are modeled to represent the general size, shape and location
- Tolerances are relatively loose and often ranges between ±50 mm to ±100 mm
- Suitable for feasibility studies and early design planning
This level is not intended for coordination or construction accuracy.
2) LOD 300 – Design-Accurate Geometry
LOD 300 requires elements to be modeled with accurate dimensions and locations based on the point cloud.
- Walls, floors, columns and major MEP components align closely with the scan data
- Typical tolerances falls within ±20 mm to ±30 mm
- Ideal for design development and coordination workflows
This is the most commonly requested level in renovation and retrofit projects.
3) LOD 350 – Coordination-Focused Modeling
At LOD 350, models include interfaces between the systems and are suitable for clash detection.
- Architectural, Structural as well as MEP components are modeled with precise spatial relationships
- Tolerances are tightened to ±10 mm to ±20 mm
- Critical penetrations, clearances and connections are clearly defined
This level is essential for multi-trade coordination and constructability reviews.
4) LOD 400 – Fabrication-Level Accuracy
LOD 400 models support fabrication and installation activities.
- Elements are modeled to reflect exact sizes, shapes and locations
- Tolerances are very strict, typically range between ±5 mm to ±10 mm
- Requires high-quality scan data and disciplined modeling workflows
Not all Scan to BIM projects require LOD 400 and it should be specified only when fabrication accuracy is essential.
5) LOD 500 – Verified As-Built Conditions
LOD 500 represents the field-verified conditions after construction or installation.
- Models are validated against the site conditions and updated accordingly
- Tolerances are minimal and reflects the real-world verification rather than design intent
- Used primarily for the facilities management and asset documentation
This level focuses more on accuracy confirmation than the geometric refinement.
Best Practices for Defining Modeling Tolerances
To ensure successful Scan to BIM outcomes:
- Clearly document the tolerance requirements in the BIM Execution Plan (BEP)
- Define tolerances per element category instead of applying a single global value
- Avoid over-modeling elements beyond the intended LOD
- Validate models through regular point cloud overlay checks
- Communicate limitations of scan data early in the project lifecycle
Well-defined tolerances reduces the reworks and eliminates the ambiguity during reviews.
Why Tolerance Definition Matters?
Without clearly defined tolerances, Scan to BIM deliverables can suffer from scope creep, unrealistic accuracy expectations and coordination issues. Proper tolerance planning ensures that the BIM model is reliable, efficient to produce and aligned with the project goals—whether it is for design, coordination or long-term asset management.
Organizations offering Scan to BIM Services must balance the accuracy, usability and efficiency to deliver the models that truly supports the downstream workflows. Similarly, professional Point Cloud to BIM Services relies heavily on the tolerance clarity to maintain consistency and quality across the different LOD requirements.
Conclusion
Defining modeling tolerances are a strategic choice that affects project costs, timelines and the usability of BIM outputs. By aligning tolerances with the LOD requirements from 200 to 500, project teams can ensure that the Scan to BIM models are accurate, fit-for-purpose and valuable throughout the building lifecycle.
Clear tolerance definitions leads to better coordination, fewer assumptions and more confident decision-making in every Scan to BIM project.
