This is a delivery-method resource, not project-specific design. Electrical protection, cable sizing, cooling capacity, fire strategy and structural loads require the appointed designers and the applicable codes. Technical review of this cluster by a named senior BIM/MEP lead is pending; do not treat it as sealed guidance.
Clash detection without classification produces noise. A raw Navisworks report with thousands of interferences does not tell the team what matters, who owns it, or when it needs resolution. A clash classification matrix defines the taxonomy — types, priorities, owners and statuses — so that raw detections become an actionable issue register.
Why classification matters
Clash detection tools find geometric interference. They do not judge significance. A pipe passing through a duct is the same to the software whether it is a critical CHW main or a minor branch. Classification adds judgment: what type of clash, how urgent, who fixes it.
- Reduces noise — duplicates, trivial items and model artefacts are filtered or grouped.
- Enables prioritisation — critical clashes get attention before minor ones.
- Assigns ownership — named discipline leads, not vague MEP responsibility.
- Tracks resolution — status progression shows whether issues are closing.
Clash types
Clash type definitions
| Type | Definition | Example | Treatment |
|---|---|---|---|
| Hard clash | Physical intersection of solid geometry | Pipe through steel beam | Must resolve — installation physically impossible |
| Soft clash (clearance) | Violation of a defined spatial envelope | Containment within switchgear access zone | Must resolve or formally accept with documented rationale |
| Tolerance clash | Elements within a specified proximity but not intersecting | Two pipes at boundary of acceptable separation | Review — may require adjustment or acceptance |
| Duplicate | Same element modelled twice at same location | Two identical hangers overlapping | Model cleanup — not a coordination issue; pollutes reports |
| Workflow clash | Interference that arises from incomplete modelling sequence | Placeholder vs detailed element; superseded geometry | Filter or defer — not a real conflict |
Priority levels
Not all clashes are equally urgent. Priority reflects impact and timing.
Priority level definitions
| Priority | Criteria | Resolution expectation |
|---|---|---|
| Critical | Blocks fabrication, installation or code compliance; no workaround | Resolve before next coordination cycle |
| High | Significant conflict requiring design change; affects schedule if delayed | Resolve within two coordination cycles |
| Medium | Conflict requiring adjustment; workaround possible but undesirable | Resolve before design freeze |
| Low | Minor conflict; acceptable workaround exists; documentation sufficient | Resolve or document acceptance before construction |
| Info | Noted for awareness; no action required; model artefact or future consideration | No resolution required; may close with note |
Priority assignment requires judgment. The BIM manager or coordination lead typically assigns initial priority; discipline leads may request re-prioritisation with rationale.
Ownership assignment
Every classified issue needs a named owner — the party responsible for resolution. Ownership rules:
- Owner is a discipline lead or firm, not a generic label — MEP is not an owner.
- The discipline whose element is more easily relocated typically owns the issue (but this is a starting point, not a rule).
- Disputed ownership escalates to the coordination lead or design team lead.
- Owner is responsible for proposing a resolution; acceptance may require other parties agreement.
Workflow statuses
Issues progress through statuses from detection to closure. Standard status progression:
Issue status definitions
| Status | Meaning | Who sets it |
|---|---|---|
| New | Clash detected; not yet reviewed or classified | System (automatic on detection) |
| Active | Issue classified, prioritised and assigned; resolution in progress | Coordinator after review |
| Resolved | Owner has updated model; claims issue is fixed | Owner (discipline lead) |
| Verified | Coordinator confirms clash no longer exists in federation | Coordinator after test |
| Closed | Issue archived; resolution documented | Coordinator |
| Accepted | Issue will not be resolved; variance accepted with documented rationale | Coordinator with approvals |
Resolved does not mean closed. Verification by the coordination lead — retesting the federation — confirms the resolution. Otherwise resolved issues reopen next week.
Example clash classification matrix
The following table illustrates a classification structure. Adapt to project-specific test pairs and ownership rules defined in the BEP.
Example DC clash classification matrix
| Test pair | Clash type | Default priority | Default owner | Notes |
|---|---|---|---|---|
| Structure vs MEP (any) | Hard | High | MEP discipline causing clash | Structure typically fixed; MEP reroutes |
| Containment vs pipework | Hard | High | Last discipline to model | Establish routing priority early |
| Switchgear clearance vs all | Soft (clearance) | Critical | Discipline intruding on clearance | Safety and code compliance |
| Generator envelope vs all | Soft (clearance) | Critical | Discipline intruding on clearance | Maintenance access required |
| CRAH coil-pull vs containment | Soft (clearance) | High | Containment lead | Routine maintenance access |
| A-path vs B-path electrical | Soft (separation) | Critical | Electrical lead | Redundancy integrity |
| Fire suppression vs all | Hard | High | Other discipline | Suppression coverage cannot compromise |
| Hangers vs hangers | Hard / duplicate | Medium | Last discipline to model | May require combined trapeze |
Using the matrix in practice
- Define the matrix in the BEP before coordination begins — test pairs, types, default priorities, default ownership.
- Run clash detection with the defined test pairs (not all-vs-all).
- Classify results — filter duplicates and workflow clashes; group related items into issues.
- Assign type, priority and owner per the matrix rules; override where judgment requires.
- Track status through resolution, verification and closure.
- Report metrics — open by priority, aging, close-out rate — to assess coordination health.
FAQ
- Should we include tolerance values in the matrix?
- The matrix defines the test pairs and types. Tolerance values (e.g. mm buffer for soft clashes) are set in the clash-detection tool configuration. Document them in the BEP or a coordination appendix — not in this classification matrix, which is about categorisation and ownership.
- Who decides disputed ownership?
- The coordination lead makes the call for routine disputes. Complex or high-impact disputes escalate to the design team lead or project manager. Document escalation decisions.
- How do we handle clashes that span multiple disciplines?
- Assign a single owner for resolution coordination, typically the discipline with the most flexibility. Other affected disciplines review and approve the proposed resolution.
- Can we change the matrix mid-project?
- Yes, with documented revision. Early-stage projects may refine the matrix as congestion areas become clearer. Issue a revised BEP section and communicate the change to the team.
Sources
- 1. Autodesk, Overview of Clash Detective Tool (2026). https://help.autodesk.com/cloudhelp/2026/ENU/Navisworks-Clash-Detective/files/GUID-36D9904E-12F3-4F82-8DD3-C2103DB0BC29.htm. Accessed 2026-09-03.
- 2. ISO, ISO 19650-1:2018 — Organization and digitization of information about buildings and civil engineering works, including building information modelling (BIM) — Part 1: Concepts and principles (2018). https://www.iso.org/standard/68078.html. Accessed 2026-09-03.
- 3. ISO, ISO 19650-2:2018 — Information management using building information modelling — Part 2: Delivery phase of the assets (2018). https://www.iso.org/standard/68080.html. Accessed 2026-09-03.
- 4. BSI, ISO 19650 — Building Information Modelling (BIM) (2026). https://www.bsigroup.com/en-GB/products-and-services/standards/iso-19650-building-information-modelling-bim/. Accessed 2026-09-03.