BIM COORDINATION CLASH DETECTION: STEP-BY-STEP PROCESS FOR MEP PROJECTS

A single undetected clash between a 400mm HVAC duct and a structural beam can cost $12,000-$18,000 in field rework.

Multiply that across the dozen, sometimes hundreds of potential clashes in a typical commercial project, and the cost of poor coordination becomes staggering.

BIM clash detection isn't just a "nice to have" quality check. It's the difference between smooth construction and costly delays, between confident site teams and constant RFIs, between projects that finish on time and those that drag on for months.

Yet many projects still approach clash detection reactively,running quick checks before submissions rather than implementing systematic coordination workflows that prevent clashes from occurring in the first place.

This guide walks through a proven step-by-step BIM clash detection process specifically for MEP projects, covering everything from model federation setup to clash resolution workflows that actually work.

Why MEP Projects Need Rigorous Clash Detection?

The MEP Challenge

MEP (Mechanical, Electrical, Plumbing) systems face unique coordination challenges:

Complexity factors:

• Multiple disciplines competing for the same spaces
• Gravity-dependent systems (drainage) with limited routing flexibility
• Size constraints: Ducts and pipes range from 25mm to 1200mm+ diameter
• Code requirements: Fire separation, access clearances, maintenance zones
• Concealed installation: Most services hidden in ceilings, walls, risers

Coordination hierarchy conflicts:

• Structure needs take priority (can't be moved)
• Fire services have strict compliance requirements
• HVAC requires specific slopes and clearances
• Hydraulics must maintain fall
• Electrical is most flexible but still needs access

The statistics:

• Average commercial project: 150-300 legitimate clashes identified in first coordination
• Without BIM coordination: 60-70% of clashes discovered during construction
• With proper coordination: Less than 5% of clashes reach site

Field resolution cost:

• Minor clash (re-route small service): $800-$2,500
• Moderate clash (re-fabricate duct/pipe section): $3,000-$8,000
• Major clash (structural interference): $12,000-$35,000
• Schedule impact: 2-5 days per major clash

The 7-Step BIM Clash Detection Process

Step 1: Model Federation Setup

Objective: Combine all discipline models into a single coordinated environment.

Actions:

1.1 Gather Current Models

• Architecture (Revit/ArchiCAD)
• Structure (Revit/Tekla)
• Mechanical (Revit MEP)
• Electrical (Revit MEP)
• Plumbing/Fire (Revit MEP)
• Civil (if relevant for site services)

1.2 Verify Model Currency

• Check revision dates and issue status
• Confirm all consultants on same design stage
• Flag any models more than 1 week old

1.3 Federation in Navisworks

• Append all models into single NWF (Navisworks File Set)
• Verify coordinate system alignment
• Check that all elements appear correctly
• Confirm units are consistent (all metric for Australian projects)

Pro tip: Create standardized folder structure for model federation files,makes updates and version tracking infinitely easier.

Typical structure:

/Project_BIM_Coordination/

  /01_Source_Models/

    /Architecture/

    /Structure/

    /MEP_Mechanical/

    /MEP_Electrical/

    /MEP_Plumbing/

  /02_Federated_Models/

  /03_Clash_Reports/

  /04_Resolved_Clashes/

Step 2: Define Clash Detection Rules

Objective: Set up intelligent clash tests that identify real conflicts, not false positives.

2.1 Establish Coordination Hierarchy

Standard priority order:

1. Structure (beams, columns, slabs, walls)
2. Fire services (sprinklers, fire-rated penetrations)
3. Mechanical (supply/return ducts, major equipment)
4. Plumbing/Hydraulic (drainage with slope requirements)
5. Electrical (cable trays, conduits,most flexible)

2.2 Create Clash Test Matrix

Essential clash tests for MEP:

Test 1: MEP vs. Structure

• All MEP disciplines against structural elements
• Critical clash,highest priority resolution

Test 2: Mechanical vs. Other MEP

• HVAC ducts vs. electrical trays
• HVAC ducts vs. plumbing/fire pipes
• Identifies service routing conflicts

Test 3: Plumbing/Fire vs. Electrical

• Pipes vs. cable trays and conduits
• Critical for ceiling space coordination

Test 4: MEP Services vs. Architecture

• Services vs. door swings, ceiling heights
• Services vs. internal walls and partitions
• Identifies access and clearance issues

Test 5: MEP Clearance Zones

• Maintenance access clearances
• Equipment service zones
• Code-required separation distances

2.3 Define Tolerance Settings

Not all overlaps are real clashes:

Clearance tolerances:

• Hard clash (physical overlap): 0mm tolerance
• Soft clash (clearance violation): 50-100mm buffer
• Ducts to structure: 100mm minimum clearance
• Pipes to structure: 75mm minimum clearance
• Services to services: 50mm minimum clearance

Element exclusions:

• Exclude clashes between same-discipline elements (handled internally)
• Exclude deliberate penetrations (doors, windows)
• Exclude minor elements (small bore pipes <50mm, lighting fixtures)

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Step 3: Run Initial Clash Detection

Objective: Generate comprehensive clash report for review.

3.1 Execute Clash Tests

In Navisworks:

• Run all defined clash tests
• Set to "hard clash" mode initially
• Generate clash report with visual previews
• Export results to BCF (BIM Collaboration Format) or XML

3.2 Initial Clash Count Analysis

Typical first-run results (mid-size commercial):

• 300-500 clashes: Expected for well-coordinated models
• 500-1000 clashes: Moderate coordination needed
• 1000+ clashes: Significant coordination issues,may indicate design development incomplete

Red flags:

• Single test generating 500+ clashes (suggests systematic issue)
• High percentage of structure vs. MEP clashes (design stage mismatch)
• Excessive false positives (detection rules need refinement)

3.3 Categorize Clashes by Severity

Critical (resolve immediately):

• Structural beam through major duct
• Column through equipment location
• Fire-rated wall penetration violations

High Priority (resolve this coordination cycle):

• Service-to-service conflicts in congested zones
• Clearance violations affecting access
• Multiple related clashes in same area

Medium Priority (resolve before next submission):

• Minor clearance violations with simple solutions
• Isolated conflicts with flexible re-routing options

Low Priority (monitor, may self-resolve):

• Clearance violations with generous margins
• Clashes in areas likely to change in design evolution

Step 4: Clash Review Workshop

Objective: Collaborative resolution session with all disciplines.

4.1 Pre-Workshop Preparation

Distribute clash report 48 hours before meeting:

• Summary statistics by discipline
• Critical clashes requiring immediate attention
• Area-specific clash groups
• Clash visualization snapshots

Assign preliminary resolution responsibility:

• MEP disciplines review clashes affecting their systems
• Identify which discipline should "move" for each clash
• Flag clashes requiring design team decision

4.2 Coordination Meeting Agenda

Typical 2-hour session structure:

0:00-0:15 - Review clash statistics and trends
0:15-1:00 - Critical clash resolution discussion
1:00-1:30 - High priority clash assignment
1:30-1:50 - Medium priority review
1:50-2:00 - Action items and next coordination date

4.3 Resolution Documentation

For each clash, document:

• Clash ID (from Navisworks report)
• Responsible discipline for resolution
• Resolution strategy (re-route, resize, relocate)
• Due date for model update
• Status (assigned, in-progress, resolved, accepted)

Use collaborative tools:

• BIM 360/ACC Issues module
• Shared Excel tracker with clash IDs
• BCF file format for direct model linking

Step 5: Model Updates and Re-Coordination

Objective: Implement clash resolutions and verify fixes.

5.1 Discipline Model Updates

Each discipline updates their models per assigned resolutions:

Mechanical example resolutions:

• Re-route duct around structural beam (change elevation or horizontal path)
• Reduce duct size in congested area (verify airflow calculations maintained)
• Relocate VAV box to avoid clash with cable tray

Electrical example resolutions:

• Shift cable tray to avoid clash with plumbing (most flexible service)
• Re-route conduit around fire sprinkler piping
• Adjust lighting layout to maintain ceiling clearances

Plumbing/Hydraulic considerations:

• Maintain required fall for drainage (typically 1:100 minimum)
• Verify trap locations still accessible
• Ensure sprinkler coverage maintained after re-routing

5.2 Model Update Protocol

Best practices:

• Issue updated models within agreed timeframe (typically 5-7 business days)
• Include revision notes describing clash resolutions
• Highlight changed areas for reviewer attention
• Update internal coordination status before re-issuing

Step 6: Clash Re-Detection and Validation

Objective: Verify clash resolutions effective and no new clashes introduced.

6.1 Update Federated Model

• Replace previous discipline models with updated versions
• Verify all models load correctly with consistent coordinates
• Check revision dates match expected updates

6.2 Re-Run Clash Tests

Focus on:

• Previously identified clashes (should now be resolved)
• Areas where model changes occurred (check for new clashes)
• Adjacent spaces to resolved clashes (verify no cascade effects)

6.3 Status Classification

For each previously identified clash:

• ✅ Resolved: Clash no longer appears in detection
• ⚠️ Partially Resolved: Reduced but still present
• ❌ Unresolved: No change detected
• 🆕 New Clash: Model update created different conflict

6.4 New Clash Analysis

New clashes after resolution indicate:

• Resolution created secondary conflict (needs redesign)
• Model update in unrelated area introduced issue
• Tolerance settings need adjustment
• False positive from updated geometry

Target metrics:

• 80%+ resolution rate in first coordination cycle
• Less than 10% new clashes introduced
• Zero critical clashes unresolved after second cycle

Step 7: Documentation and Iteration

Objective: Track progress and establish continuous coordination workflow.

7.1 Create Clash Resolution Report

Include:

• Clash count summary (previous vs. current)
• Resolution statistics by discipline
• Critical unresolved clashes requiring escalation
• New clash analysis
• Next coordination meeting date

7.2 Update Coordination Register

Master tracking document includes:

• All clash detection cycles with dates
• Clash count trends over time
• Discipline-specific resolution performance
• Outstanding action items
• Model version history

7.3 Establish Coordination Cadence

Typical schedules:

Design Development: Bi-weekly coordination (every 2 weeks)
Construction Documentation: Weekly coordination
Pre-Construction: Daily or continuous coordination for critical areas

7.4 Continuous Improvement

After each cycle, refine:

• Clash detection rules (reduce false positives)
• Meeting efficiency (focus time on critical items)
• Resolution turnaround times
• Communication protocols

Common Clash Detection Pitfalls and Solutions

Pitfall #1: False Positive Overload

Problem: Thousands of meaningless clashes obscure real conflicts.

Causes:

• Detection tolerance too sensitive
• Generic objects (walls, floors) creating massive clash counts
• Small elements included unnecessarily

Solution:

• Refine tolerance settings (50-100mm for clearances)
• Exclude architectural walls/floors from MEP vs. Architecture tests
• Filter out elements below meaningful size threshold
• Use "Search Sets" to focus detection on critical elements

Pitfall #2: "Assign and Forget" Syndrome

Problem: Clashes assigned but never actually resolved.

Causes:

• No accountability tracking
• Unrealistic resolution timelines
• Insufficient design team authority to make changes

Solution:

• Clear ownership and due dates for every clash
• Regular status tracking between coordination meetings
• Escalation protocol for overdue items
• Project leadership involvement for contentious resolutions

Pitfall #3: Coordination Theater

Problem: Going through motions but not achieving real coordination.

Symptoms:

• Same clashes appearing in multiple coordination cycles
• High clash count never meaningfully reduces
• Resolutions not reflected in updated models

Solution:

• Make coordination meetings decision-making forums, not status reports
• Require model updates before next meeting (no excuses)
• Leadership accountability for discipline coordination performance

Software Tools and Workflows

Primary Coordination Platform: Navisworks

Key features for clash detection:

• Multi-format model federation (Revit, IFC, DWG, etc.)
• Comprehensive clash detection engine
• Visual clash review and markup
• BCF export for issue tracking
• Timeline/4D simulation for phasing coordination

Typical workflow:

1. Append models → 2. Run clash tests → 3. Review results → 4. Export BCF → 5. Track resolutions

Alternative/Supplementary Tools

BIM 360/Autodesk Construction Cloud:

• Cloud-based model coordination
• Built-in clash detection
• Integrated issue tracking
• Mobile access for site teams

Solibri:

• Rule-based model checking
• Quality control validation
• Code compliance checking
• Stronger in quality checking than pure clash detection

BIMcollab:

• BCF issue management
• Open standard compatibility
• Good for multi-platform projects

Frequently Asked Questions

How often should we run clash detection during a project?

Depends on project stage:

• Schematic Design: Monthly or at major milestones
• Design Development: Bi-weekly (every 2 weeks)
• Construction Documentation: Weekly
• Pre-Construction/Early Construction: Continuous or daily for active areas

Rule of thumb: Increase frequency as design progresses and cost of changes increases.

What's an acceptable final clash count before construction?

Target: Zero hard clashes, minimal soft clashes.

Realistic outcomes:

• 0-20 soft clashes: Excellent coordination (minor clearance issues only)
• 20-50 soft clashes: Good coordination (clearances manageable on site)
• 50-100 soft clashes: Acceptable for complex projects (requires field coordination plan)
• 100+ clashes or any hard clashes: Coordination incomplete,do not proceed to construction

All remaining clashes should have documented resolution strategies or acceptance by design team.

Who should attend coordination meetings?

Essential attendees:

• Lead architect/designer
• Structural engineer
• MEP discipline leads (mechanical, electrical, plumbing/fire)
• BIM coordinator/manager
• General contractor (construction phase)

Optional based on project:

• Specialty consultants (facade, acoustics, fire)
• Key subcontractors (MEP trades)
• Client/project manager for critical decisions

Keep meetings focused,typically 6-10 people maximum for effective decision-making.

Can clash detection replace traditional coordination drawings?

No,they're complementary.

Clash detection identifies: Physical conflicts and clearance violations
Coordination drawings communicate: Resolution strategies and installation sequences

Best practice: Use clash detection to identify issues, use coordination drawings to document approved solutions for construction teams.

Conclusion:

The Value of Systematic Coordination

BIM clash detection isn't magic,it's a systematic process that requires discipline, collaboration, and continuous refinement.

The seven-step process recap:

1. ✓ Model Federation Setup
2. ✓ Define Clash Detection Rules
3. ✓ Run Initial Clash Detection
4. ✓ Clash Review Workshop
5. ✓ Model Updates and Re-Coordination
6. ✓ Clash Re-Detection and Validation
7. ✓ Documentation and Iteration

The payoff:

• 60-80% reduction in field coordination issues
• 15-25% fewer RFIs during construction
• 2-4 weeks saved on a typical commercial project schedule
• $50,000-$200,000 prevented rework costs per project

The key is commitment to the process, to collaboration, and to resolving issues in the model rather than on site.

Projects that embrace rigorous BIM coordination don't just avoid problems; they set new standards for construction efficiency and quality.

Need Expert BIM Coordination Support?

Obelisk provides comprehensive BIM coordination services for MEP projects.

✓ Federated Model Management: Multi-discipline coordination in Navisworks/ACC
✓ Clash Detection Services: Systematic testing and reporting
✓ Coordination Facilitation: Expert-led resolution workshops
✓ Model Updates: Post-coordination documentation refinement
✓ Compliance: Australian standards and NCC requirements

We help project teams achieve clash-free documentation before construction starts.

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📧 Discuss Your Project: Contact Us‍‍

Reading Time: ~10 minutes
Target Audience: BIM Managers, MEP Coordinators, Project Engineers
Conversion Goal: BIM coordination service inquiry