What is the difference between a hard clash and a soft clash in BIM?

A hard clash occurs when two solid building elements physically overlap in the model — for example, a structural beam intersecting a duct. A soft clash (also called a clearance clash) occurs when two elements do not intersect but violate a required minimum separation distance, such as a pipe that is too close to a beam for required insulation thickness or maintenance access. Both types must be resolved before construction.

How do I export a Navisworks NWC file from Revit?

In Revit, go to File > Export > NWC. In the export dialog, set coordinates to Shared Coordinates so the NWC aligns with other discipline files in Navisworks. Enable 'Convert linked files' to export linked models as separate NWC objects. Choose 'Entire project' as the export scope for coordination purposes. The resulting .nwc file can then be appended into a Navisworks aggregated coordination model.

What is ACC Model Coordination and how is it different from Navisworks?

ACC (Autodesk Construction Cloud) Model Coordination is a cloud-based clash detection platform where models are uploaded to the cloud and clashes are detected and tracked automatically online. Navisworks is a desktop application requiring manual NWC exports and local file management. ACC provides stronger issue assignment and tracking workflows; Navisworks provides more control over test configuration, clash grouping, and 4D schedule integration. Large GC teams often use both — ACC for owner-facing coordination and Navisworks for in-depth trade coordination.

How much money can clash detection save on a construction project?

Research from Stanford's Center for Integrated Facility Engineering (CIFE) documents 40% reduction in unbudgeted changes and up to 10% overall cost reduction on BIM-coordinated projects. Holder Construction's published data shows $10 in field savings for every $1 spent on BIM coordination. On a $50M commercial project, finding and resolving 200 clashes in the model rather than in the field can realistically save $500,000 to $2M in rework costs, crane time, and schedule delay.

What Navisworks clash tolerance should I use for MEP coordination?

Common tolerance settings depend on the system: use 0.0 inches (hard clash) for bare pipe-to-structure conflicts; 1 inch for PVC conduit and small diameter piping with vapor barrier; 2 inches for insulated hot/cold water piping; 3–4 inches for insulated chilled water and refrigerant piping to account for pipe insulation plus air gap; and 6–12 inches for ductwork in tight ceiling spaces where sheet metal workers need swing clearance. Always document your tolerance standards in the BIM Execution Plan.

Can Navisworks do 4D construction scheduling clash detection?

Yes. Navisworks TimeLiner module allows you to attach a construction schedule (imported from Primavera P6, MS Project, or CSV) to model elements. You can then run Clash Detective tests against time-based selection sets to identify when two activities require the same physical space simultaneously. Common 4D clashes include crane reach conflicts, temporary works versus permanent structure, and multiple subcontractors sequenced in the same bay on the same day.

Construction·11 min read·June 19, 2026

⚠️ Clash Detection in BIM: Navisworks vs. Autodesk Construction Cloud (BIM 360) Explained

A comprehensive guide to BIM clash detection — the three clash types, Revit's built-in Interference Check, Navisworks Clash Detective setup and reporting, ACC Model Coordination issue management, tool comparison, and the real cost savings data that makes the business case for BIM coordination.

📖Structural Engineering Drawing Set — Illustrated Reader (Full Access)

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What Is Clash Detection and Why It Matters

Clash detection is the automated process of identifying spatial conflicts between building elements modeled by different disciplines — finding where a structural beam intersects a duct, where a sprinkler pipe runs through a concrete column, or where two conduit runs fight for the same ceiling space. In traditional 2D coordination, these conflicts were discovered in the field during construction, where fixing them costs 10 to 100 times more than resolving them in the model. A McKinsey analysis of large construction projects found that 98% of megaprojects exceed budget, and rework driven by coordination failures is consistently cited as a top-five cost driver.

Topics covered

clash detection BIMNavisworks Clash DetectiveBIM 360 Model CoordinationAutodesk Construction Cloud clashhard clash soft clashRevit Interference CheckNWC export RevitBIM coordination clash reportACC clash detectionclash detection workflowAEC coordination meetingMEP coordination clash