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Top 5 MEP vs. structural clashes

The most expensive coordination failures happen where MEP systems meet structure. These clashes cause delays, change orders, and field rework. Learn where they happen and how to prevent them.

Understanding Clash Types
Hard Clash
Physical overlap between two elements, a duct intersecting a beam, pipe through a column. These must be resolved; the building cannot be constructed as drawn.
Soft Clash (Clearance)
Elements don't physically touch but violate required clearances, not enough space for insulation, maintenance access, or code-required separations.
Workflow/4D Clash
Installation sequence conflicts, one trade cannot install their work because another trade's incomplete work is in the way. Common with ceiling systems.

The Most Common Clashes

1

Ductwork vs. Structural Beams

HVAC + StructuralHigh Impact

Main supply and return ducts often run perpendicular to structural framing, creating conflicts at beam intersections. This is the most common and costly clash on commercial projects.

Common Causes
Ceiling plenum height assumed without verifying beam depths
Duct sizes increased during design development without re-routing
Structural engineer adds moment connections that deepen beams
Mechanical contractor selects different equipment with larger duct connections
Prevention Strategies
Establish ceiling plenum zone early with beam bottom elevations
Route major ducts parallel to beams in corridors
Request structural beam schedule before mechanical design
Add 6" vertical buffer in BIM clash detection tolerance
2

Plumbing Risers vs. Structural Columns

Plumbing + StructuralHigh Impact

Vertical plumbing stacks and structural columns compete for the same core locations. Moving either element post-construction is extremely expensive.

Common Causes
Restroom stacks not coordinated with column grid
Columns shifted during structural optimization
Multiple chase locations shown on different drawing sets
Plumbing designer using outdated architectural backgrounds
Prevention Strategies
Lock vertical chase locations in schematic design phase
Require plumbing designer to overlay structural column grid
Create dedicated coordination drawings for core areas
Include chase locations in early interdisciplinary reviews
3

Conduit/Cable Tray vs. Beams & Joists

Electrical + StructuralMedium Impact

Electrical conduit runs and cable trays frequently conflict with secondary structural framing, particularly bar joists and composite deck framing.

Common Causes
Electrical designer routes conduit at constant elevation
Bar joist depth not accounted for in routing
Large conduit runs added for data/low voltage late in design
Equipment locations move, requiring re-routing through structure
Prevention Strategies
Route large conduit runs in dedicated corridors
Verify joist bottom elevations before conduit routing
Reserve chase locations through bar joist bays
Consider cable tray for flexibility in routing
4

Fire Sprinkler Mains vs. Structure

Fire Protection + StructuralHigh Impact

Fire protection mains and branch lines must maintain proper pitch for drainage while navigating around beams. Conflicts often discovered during installation.

Common Causes
Sprinkler design completed after structural steel fabrication
Branch line pitch requirements forgotten in tight plenums
Main drain locations conflict with footings or grade beams
Sprinkler heads centered in ceiling tiles hit beams above
Prevention Strategies
Include fire protection in early design coordination
Route mains parallel to structural bays
Verify head locations against beam layout
Coordinate drain-down and test connections with site civil
5

Mechanical Equipment on Structure

Mechanical + StructuralMedium Impact

Rooftop units, air handlers, and pumps require structural support that is often undersized or mislocated, especially when equipment is selected late.

Common Causes
Equipment weights estimated low in early design
Vibration isolation requirements not communicated
Equipment pads shown schematically, not coordinated with structure
Dunnage and curbs added without structural review
Prevention Strategies
Require mechanical equipment schedule with weights early
Coordinate housekeeping pad locations with slab reinforcing
Include vibration isolation in structural loading
Review equipment anchorage and seismic requirements

Clash Detection Best Practices

Run Checks Early & Often
Don't wait for 100% CD. Run clash detection at 50% DD, 100% DD, 50% CD, and 100% CD. Early clashes are cheap to fix.
Set Realistic Tolerances
Hard clashes need 0" tolerance. Soft clashes for maintenance access might need 18-24". Insulation clearances need 2-4".
Assign Clash Ownership
Every clash needs one responsible party. Unassigned clashes don't get resolved. Track resolution status weekly.
Focus on High-Value Areas
Mechanical rooms, vertical shafts, and ceiling plenums cause 80% of coordination issues. Prioritize these zones.
Attribution

Based on industry coordination best practices and common construction project data. Every project is unique, always conduct project-specific coordination reviews.

Keep exploring

More guides and tools for catching clashes before the field.

How to Find Clashes in 2D Drawings

Step-by-step techniques for identifying coordination conflicts from PDFs.

How to Create a Clash Detection Report

Document conflicts in a way that gets them resolved.

Feature: AI Clash Detection

Catch MEP-structural conflicts automatically from 2D PDFs.

2D vs 3D Clash Detection

When to use PDF analysis vs full BIM coordination.

How to Prepare for a Coordination Meeting

Where MEP-structural clashes get discussed and resolved.

AI vs BIM Clash Detection

How AI approaches compare to traditional BIM coordination.

Catch clashes before they cost you

Don't have time to manually overlay every structural and MEP sheet? Helonic's AI scans your PDFs and identifies potential coordination conflicts in seconds, without expensive BIM software or 3D modeling. Find clashes on 2D drawings before they become 3D problems in the field.