What is clash detection in BIM and why does it matter on Irish projects?

Clash detection is the automated identification of conflicts between model elements from different disciplines in a federated BIM model. On Irish NDP projects, clash detection matters because ELV containment, MEP ducts, structural beams and architectural elements frequently occupy overlapping spatial zones — conflicts that are invisible in 2D drawings but visible in the federated 3D model. Resolving clashes in the model before site mobilisation eliminates the variation orders, programme delays and abortive work that constitute the most expensive coordination failure pattern on Irish building projects.

What software is used for clash detection on Irish NDP projects?

Autodesk Navisworks Manage is the dominant clash detection tool on Irish NDP projects — used by all major Irish MEP and structural consultancies, and specified in HSE and OGP EIR documents. It accepts NWC/NWD model formats from Revit, AutoCAD, Tekla and other authoring tools, and provides clash detection, clash grouping, status tracking and clash report output. Solibri Model Checker is used on some Irish projects for model quality checking alongside Navisworks. BIM Collaborate Pro (Autodesk's cloud-native coordination platform) is gaining adoption on larger Irish projects that use ACC as their CDE.

What types of clash are detected in Navisworks?

Three clash types are detected in Navisworks: (1) Hard clashes — physical penetration of one element by another (e.g., an ELV cable tray passing through a structural beam); (2) Soft clashes — spatial overlap within a defined clearance zone (e.g., an ELV tray within 150mm of an HVAC duct, violating the required maintenance clearance); and (3) Duplicate clashes — identical elements modelled twice by different disciplines. Hard clashes have zero tolerance; soft clashes are evaluated against the specific clearance requirements for each situation.

How often should clash detection be run on an Irish construction project?

Clash detection should be run at every coordination review cycle — typically fortnightly in the Stage 3 coordination phase, weekly in Stage 4 (when the model is changing rapidly before tender issue), and monthly in Stage 5 (construction) when contractor shop drawings update the model. ASDV issues clash reports within one working day of each coordination review for ELV discipline elements, with resolution proposals for each clash identified.

What is the most common ELV/MEP clash type on Irish building projects?

The most common ELV/MEP clash on Irish building projects is ELV cable tray vs HVAC ductwork in the primary ceiling void zone — typically where the ELV designer and MEP designer have both routed containment through the same limited ceiling void space without coordination. This clash type accounts for approximately 60% of all ELV-related variation orders on large Irish NDP projects and is entirely eliminable through Stage 3 BIM clash detection before tender.

Clash Detection in Navisworks — Irish BIM Workflow

On Irish NDP projects, unresolved BIM clashes are the single largest source of contractor variation orders. ELV cable tray routes that conflict with HVAC ductwork. Fire alarm containment that penetrates structural beams. Access control door hardware that clashes with MEP pipework in service corridors. These conflicts are invisible in 2D drawings — they only become apparent when the 3D discipline models are federated and clash detection is run in Navisworks. This guide covers the Navisworks clash detection workflow for Irish BIM projects, the types of clash, the ELV/MEP clash patterns that appear on virtually every Irish construction project, and how ASDV manages clash detection for Irish clients.

What Is Clash Detection and Why Does It Matter in Ireland?

Clash detection is the automated identification of conflicts between model elements from different disciplines in a federated BIM model. When the ELV containment model, the MEP ductwork model, the structural model and the architectural model are combined in Navisworks, the software compares every element against every other element — identifying where two elements occupy the same physical space (hard clash) or violate a required clearance zone (soft clash).

On Irish NDP projects, the value of clash detection is straightforward: resolving a conflict in the BIM model at Stage 3 costs a few hours of engineering time. Resolving the same conflict on site at Stage 5 — after structural elements are cast, MEP services are installed and ELV containment is being routed — costs tens of thousands of euros in rerouting, abortive work and programme delay.

60%

The approximate proportion of ELV-related variation orders on large Irish NDP projects that originate from ELV containment vs HVAC ductwork clashes in ceiling voids — a conflict type that is entirely eliminable through Stage 3 BIM clash detection before tender issue.

Setting Up the Federated Model in Navisworks

Before clash detection can run, the federated model must be correctly set up. All discipline models must: share a common coordinate origin (confirmed in the BEP and set at project inception — not at Stage 3); be published in compatible formats (NWC from Revit, NWC from AutoCAD, IFC from other tools); have current revision and status confirmed (running clash detection against superseded models wastes time and generates false results); and be loaded into a single Navisworks file that represents the complete building at the current design stage.

Clash Types: Hard Clashes, Soft Clashes and Clearance Clashes

Hard Clashes — Physical Object Penetration

A hard clash occurs when two model elements physically occupy the same space — a cable tray passes through a structural beam, a fire alarm panel is positioned inside a wall, a CCTV camera bracket conflicts with MEP pipework. Hard clashes have zero tolerance: every hard clash is a design error that must be resolved before tender. On an Irish hospital or data centre project, a clean clash detection run with zero hard clashes is a significant milestone — it means the design has been properly coordinated.

Soft Clashes — Spatial Conflict Within a Clearance Zone

A soft clash occurs when two model elements are physically clear of each other but violate a required minimum clearance. ELV cable tray within 150mm of HVAC ductwork (violating installation and maintenance clearance); fire alarm cable within 50mm of mains electrical cable (violating IS 10101 segregation requirements); access control door hardware within 200mm of MEP services (violating maintenance access clearance). Soft clashes require judgement — some can be accepted; others must be resolved depending on the specific clearance requirement.

Running Clash Detection — The Navisworks Workflow

Import and Coordinate All Discipline Models

Confirm shared coordinates across all discipline models. Load current revision NWC/NWD files for all disciplines. Verify that models are correctly positioned relative to each other using the shared coordinate origin from the BEP.

Define Clash Detection Rules by Discipline Pair

Create specific clash test rules: ELV vs Structural (hard); ELV vs MEP (hard + soft with clearance rules); ELV vs Architectural (hard). Different clearance tolerances apply to different discipline pair combinations — the clash test setup must reflect these.

Run, Filter and Prioritise Clash Results

Run all clash tests. Filter out duplicate clashes, self-clashes (elements clashing with themselves in the same model) and tolerance-driven false positives. Prioritise: hard clashes first; soft clashes in primary containment zones second; lower-priority soft clashes for later coordination.

Issue Clash Reports and Track Resolution

Export clash reports in PDF and BCF format. Issue to the relevant discipline pair. Maintain a clash register tracking: clash ID, type, disciplines involved, assigned responsible party, proposed resolution, resolution status. ASDV issues ELV clash reports within one working day of each coordination review.

ELV/MEP Clashes — The Most Common Type on Irish Projects

The dominant clash type on Irish NDP projects is ELV cable containment vs MEP services — particularly HVAC ductwork and MEP pipework in primary ceiling voids. This clash type is so prevalent because: ceiling void space is finite and contested; ELV designers and MEP designers historically work independently without 3D coordination; and the RIAI programme typically leaves insufficient time for Stage 3 coordination if BIM is not part of the programme from Stage 1. On Irish hospitals, data centres in Dublin and Cork, and university campus buildings in Galway and Limerick, ASDV's BIM clash detection for ELV systems routinely identifies 50–200 clashes on a medium-sized project — all of which would otherwise become site variations.

AI-Powered Clash Detection — The 2025 State of Play

AI-powered clash detection tools are beginning to emerge — automatically classifying and prioritising clashes by severity, suggesting resolution approaches based on model context, and predicting where clashes are likely to occur in still-developing model areas. Autodesk's AI-powered coordination features in BIM Collaborate Pro, and emerging tools such as Speckle and TestFit, are moving toward real-time clash notification as models are updated. ASDV monitors and incorporates these tools on Irish NDP projects where they reduce coordination cycle time.

See our BIM support services Ireland and federated BIM model guide for the broader coordination context.

FAQs — Clash Detection Navisworks Ireland

Clash detection is automated identification of spatial conflicts between model elements in a federated BIM model. On Irish NDP projects, resolving clashes in the model at Stage 3 costs hours; resolving the same on site at Stage 5 costs tens of thousands in rerouting, abortive work and programme delay.

Autodesk Navisworks Manage is the dominant tool — specified in HSE and OGP EIR documents. Solibri Model Checker is used for model quality checking. BIM Collaborate Pro (cloud-native) is gaining adoption on ACC-based Irish projects.

Three types: Hard clashes (physical penetration — zero tolerance); Soft clashes (clearance zone violation — requires judgement based on specific clearance requirements); and Duplicate clashes (same element modelled twice). Hard clashes must be resolved before tender; soft clashes evaluated case by case.

Fortnightly in Stage 3 coordination; weekly in Stage 4 before tender issue; monthly in Stage 5 construction as contractor shop drawings update the model. ASDV issues ELV clash reports within one working day of each coordination review.

ELV cable tray vs HVAC ductwork in primary ceiling voids — approximately 60% of all ELV variation orders on Irish NDP projects. Entirely eliminable through Stage 3 BIM clash detection before tender. ASDV routinely identifies 50–200 such clashes on medium-sized Irish projects.

Get a Free BIM Clash Detection Assessment for Your Irish Project

ASDV runs ELV clash detection in Navisworks for Irish NDP projects — reports issued within one working day of each coordination review.

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ASDV Design Team

BIM Coordination Specialists — ASDV Consultant Ireland

ASDV runs ELV BIM clash detection in Navisworks for Irish NDP projects — LOD 300 ELV models, clash reports within one working day, and CDE-tracked resolution process. Remote delivery from New Delhi.