Clash Matrix & BIM Coordination

Clash classification, MEP right-of-way, BCF workflow — Vietnam practice per ISO 19650

Hard Clash

critical

Two objects intersect geometrically (intersecting volume > 0). E.g. pipe through beam, column overlapping wall. Tolerance 0–10mm to filter Revit rounding noise.

Auto-detectableST2, ST3, ST4

Clearance / Soft Clash

major

Objects don't touch but violate minimum required clearance for installation, maintenance, or safety codes. Navisworks creates a buffer zone around each object.

Auto-detectableST3, ST4

4D / Workflow Clash

major

Two construction activities occupy the same space or resource simultaneously. Requires Navisworks TimeLiner or Synchro integration to detect.

Manual reviewST4

Duplicate Clash

info

Same object modeled twice by two disciplines — not a real conflict, but causes quantity and reporting errors. Common when teams share models without clear boundaries.

Auto-detectableST2, ST3, ST4

False positive advisory

Raw Navisworks clashes (All-vs-All) are typically very numerous. Use Named Search Sets + Ignore Rules + appropriate tolerances per discipline (5mm steel, 20–25mm pipe/duct) to filter before assigning. There is no industry-standardized false positive rate — vendor documentation figures are estimates only.

Resolution Priority Matrix (Severity × Phase)

Severity / Phase	ST2 Technical	ST3 Const. Drawings	ST4 Construction
Critical — Hard clash	P2	P1 fix now	P1 fix now
Major — Clearance / 4D	P4	P3	P2
Minor — Near-miss	P5	P4	P3
False Positive	P5 Won't Fix	P5 Won't Fix	P5 Won't Fix

Hard overrides: FIRE-related clashes → P1 regardless of phase (fire code legal priority). RC beam penetrations requiring reinforcement → require structural engineer sign-off.