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 on a data-center project is the structured identification and resolution of spatial interferences between discipline models — done early enough that decisions cost hours, not site variations. The tool finds the geometry. The process decides what matters.
Why clash detection matters more in data centres
A commercial-office ceiling void may forgive a late conduit. A data-hall aisle with 2N electrical routes, high-density containment and cooling distribution does not. CIBSE's KS18 exists because data centres require integrated space planning across electrical, mechanical and structural disciplines from concept. In the model, that integration is tested by clash detection — but the test only works if the test matrix reflects the congestion.
Hard clashes vs soft clashes
Hard and soft clash distinction
| Type | Definition | Example | Resolution priority |
|---|---|---|---|
| Hard clash | Physical intersection of solid geometry | Pipe through cable tray | Must resolve before fabrication or installation |
| Soft clash (clearance) | Violation of a defined spatial buffer | Tray within switchgear rack-out zone | Must resolve unless formally accepted with rationale |
| Duplicate | Same element modelled twice | Two identical hangers at same location | Clean model, do not report as coordination issue |
Hard clashes prevent physical installation. Soft clashes — clearance or tolerance violations — prevent maintainability, safety access or code compliance. Duplicates pollute reports and train teams to ignore them. A useful test matrix treats all three differently.
Clearance envelopes as first-class objects
A switchgear panel has a front clearance for racking out breakers and a rear clearance for cable termination. A CRAH has a coil-pull envelope. A busway run requires vertical bend radii. If those envelopes are not geometry in the model — either as coordination solids or as rule-based clearances — clash detection will report clean while the maintainability problem is hidden.
- Switchgear rack-out, breaker withdrawal, rear cable entry zones.
- Generator maintenance access, fuel and exhaust service paths.
- UPS and battery replacement routes, including temporary staging.
- CRAH/CRAC coil-pull and filter-change envelopes.
- Busway elbow radii, tap-off clearances, future extension reserves.
- Valve handwheel and actuator access zones.
Classified issue workflow
A raw clash report with 4,000 items is unusable. A classified register with 40 named issues, owners and due dates is actionable. The difference is process, not software.
Detect → Classify → Assign → Resolve → Close
Original Ardaron diagram. Tooling varies by appointment.
- Detect: run the test matrix on the federated model at the agreed cadence.
- Classify: sort hard clashes from clearance violations and duplicates; group related items into issues.
- Assign: each issue has a named owner (discipline lead or firm, not MEP) and a target date.
- Resolve: owner updates the model; resolution is committed to the CDE in the appropriate state.
- Close: next federation confirms the issue no longer exists; issue is marked closed with evidence.
DC-specific test matrices
A data centre demands tests that a commercial building rarely does. The following are typical — adjust to the project scope and the BEP.
Example DC clash-test matrix
| Test | Selection A | Selection B | Type |
|---|---|---|---|
| Power vs cooling routes | Busway, containment | CHW/CW pipework | Hard + clearance |
| Containment vs structure | Cable tray, ladder | Steelwork, slabs, beams | Hard |
| Switchgear clearance | Switchgear envelopes | All MEP + structure | Soft (clearance) |
| Generator service zone | Generator envelope | All trades | Soft (clearance) |
| Hall units vs containment | CRAH/CRAC + envelopes | Containment, pipework | Hard + clearance |
| Fire protection vs all | Sprinkler, gas suppression | All trades | Hard |
| Redundant path independence | Path A electrical | Path B electrical | Soft (separation) |
The last test — redundant-path independence — is a design decision enforced spatially. If 2N or 2(N+1) logic requires A and B paths to remain physically separate, clash detection is one way to audit that they do not share a vulnerable corridor.
Tools and practical usage
Autodesk Navisworks Manage includes Clash Detective for identifying interferences across discipline models. It supports selection sets, clash rules, tolerance settings, and reporting to HTML, XML or Switchback to the authoring tool. Autodesk Construction Cloud (ACC) Model Coordination provides browser-based clash detection and issue assignment. Other tools exist (Solibri, BIMcollab, proprietary client platforms); the principles — test matrix, classification, ownership, close-out — transfer.
Common clash-detection failures
Reports run without a test matrix
Why it happens. Default all-vs-all generates noise.
Impact. Teams ignore reports; real clashes hide.
Mitigation. Define explicit test pairs before first run.
Clearance envelopes never modelled
Why it happens. Seen as optional decoration.
Impact. Zero hard clashes but plant cannot be maintained.
Mitigation. Envelopes are coordination objects, not optional.
Clashes deleted instead of resolved
Why it happens. Faster than fixing the model.
Impact. Same clash reappears every week.
Mitigation. Resolved status requires verified model update.
No named owner per issue
Why it happens. MEP listed as owner.
Impact. Nobody fixes it.
Mitigation. Owner = discipline lead or named firm.
FAQ
- Should we aim for zero clashes?
- No. Zero clashes after intelligent classification and accepted residuals is fine. Zero clashes because the test matrix is weak or issues are deleted is a false target. The objective is no unresolved hard clashes at freeze and documented acceptance for any remaining clearance items.
- How often should we run clash detection?
- The BEP should specify cadence — typically weekly or at each design-stage gate. Running daily with no time to resolve creates noise. Running once at the end finds clashes too late to fix cheaply.
- Who owns the clash report?
- The federation owner (BIM manager or coordinator) runs the test and distributes results. Individual issues are owned by discipline leads. Closing the issue requires the discipline to update their model and the coordinator to verify.
- Can clash detection replace design coordination meetings?
- No. Clash detection finds spatial interference. Design coordination resolves scope, sequence and interface responsibility. The tool is an input to the meeting, not a substitute for it.
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. CIBSE, KS18: Data Centres: An Introduction to Concepts & Design (2012). https://www.cibse.org/knowledge-research/knowledge-portal/ks18-data-centres-an-introduction-to-concepts-design/. Accessed 2026-09-03.
- 5. ASHRAE, ASHRAE Data Center Resources / TC 9.9 Datacom Series (2024). https://www.ashrae.org/technical-resources/bookstore/datacom-series. Accessed 2026-09-03.