A Soft Clash in BIM is a coordination conflict where two building elements may not physically intersect, but the required clearance, access, tolerance, or working space between them is insufficient.
Soft clashes are commonly identified during BIM coordination when an element enters a predefined clearance zone around another element. For example, equipment may have enough physical space to fit but not enough room for installation, operation, inspection, maintenance, or replacement.
Soft clashes are also commonly referred to as clearance clashes.
Soft Clash: Quick Definition
| Item | Description |
|---|---|
| Term | Soft Clash |
| Category | BIM Clash Detection |
| Meaning | A conflict caused by insufficient required clearance between BIM elements |
| Physical Intersection Required? | No |
| Common Examples | Equipment access, duct clearance, pipe insulation space, maintenance zones |
| Also Known As | Clearance Clash |
| Detected During | BIM Clash Detection and BIM Coordination |
| Common Disciplines | MEP, Structural, Architectural |
| Typical Users | BIM Coordinators, MEP Engineers, Designers, Contractors |
| Next Stage | Clash Review and BIM Clash Resolution |
What Does Soft Clash Mean in BIM?
A soft clash occurs when model elements are physically separated but do not maintain the minimum distance required for construction, installation, operation, maintenance, safety, or system performance.
Unlike a Hard Clash, where two elements physically occupy the same space, a Soft Clash is based on a defined clearance requirement.
For example:
A pipe may pass beside an air-handling unit without touching it.
However, if the pipe enters the maintenance zone required to remove the unit’s filter or access panel, it may create a Soft Clash.
This means the geometry does not physically collide, but the arrangement may still create a coordination or constructability problem.
Examples of Soft Clashes in BIM
Common examples of Soft Clashes include:
- a pipe installed too close to HVAC equipment for maintenance access
- a duct located inside the required service clearance of an electrical panel
- two insulated pipes positioned too close together
- a cable tray blocking access to a valve
- building services entering equipment replacement zones
- MEP services positioned too close to walls for installation
- inadequate clearance between ductwork and structural elements
- insufficient headroom below an MEP service
- a pipe route entering a required safety zone
- services blocking access to inspection panels
These situations may not involve direct physical overlap but can still affect construction and future building operation.
What Causes Soft Clashes?
Soft clashes can occur for several reasons during design and BIM coordination.
Insufficient Clearance Requirements
Different systems require minimum clearances for installation, insulation, operation, or maintenance.
If these requirements are not included during modelling, soft clashes can occur.
Congested MEP Spaces
Ceiling voids, risers, plant rooms, shafts, and service corridors may contain multiple systems within limited space.
Even when systems do not physically intersect, the available clearance may become insufficient.
Missing Maintenance Zones
Equipment often requires space around it for servicing, repair, inspection, or replacement.
If these maintenance zones are not modelled or considered, another service may occupy the required space.
Design Changes
Changes in equipment dimensions, service routes, structural geometry, or architectural layouts may create new clearance conflicts.
Incorrect Clash Tolerances
Clash-detection rules may use predefined tolerance or clearance values.
Incorrect settings can either miss genuine soft clashes or generate unnecessary clash results.
How Is a Soft Clash Detected?
Soft clashes are generally identified using BIM Clash Detection rules that check whether model elements enter predefined clearance zones.
Unlike hard-clash detection, the software is not only looking for physical geometry intersections.
Instead, it may evaluate:
- minimum distance between elements
- equipment access zones
- maintenance clearance
- insulation requirements
- installation space
- safety zones
- operational clearance
- project-specific coordination tolerances
A typical process includes:
- Identify the elements or systems to compare.
- Define the required clearance or tolerance.
- Run the BIM clash-detection test.
- Identify elements entering the clearance zone.
- Review whether each result represents a genuine coordination issue.
- Assign the clash to the relevant discipline.
- Resolve or approve the condition.
- Recheck the coordinated model.
For a broader explanation of the clash-detection process, link this section to your existing Clash Detection guide.
Soft Clash Example: Pipe Near HVAC Equipment
Consider an HVAC unit that requires a clear maintenance zone in front of an access panel.
A plumbing pipe may pass through this zone without physically touching the equipment.
Geometrically, there is no Hard Clash.
However, the pipe may prevent technicians from opening the panel or removing internal components.
This creates a Soft Clash.
Possible resolutions may include:
- moving the pipe
- changing its elevation
- rerouting the pipe
- relocating another service
- reviewing the required maintenance clearance
The final solution should consider both engineering requirements and future accessibility.
Soft Clash vs Hard Clash
A Soft Clash and a Hard Clash represent different BIM coordination conditions.
| Soft Clash | Hard Clash |
|---|---|
| Elements may not physically intersect | Elements physically intersect |
| Based on required clearance or tolerance | Based on geometric overlap |
| Example: pipe enters equipment maintenance zone | Example: pipe passes through structural beam |
| Requires clearance rules | Can be identified through direct geometry intersection |
| Often relates to access, maintenance or installation | Relates to physical constructability conflict |
| May require judgement about required distance | Requires removal or approval of intersection |
Simple example
Hard Clash:
A duct physically intersects a beam.
Soft Clash:
The duct clears the beam but does not leave enough space for insulation or installation.
Soft Clash vs Clearance Clash
In BIM coordination, Soft Clash and Clearance Clash are often used to describe the same general type of conflict.
Both refer to situations where elements violate a required spatial clearance even though they may not physically overlap.
For example, a project may require:
100 mm minimum clearance
between two services.
If the actual clearance becomes:
50 mm
the clash-detection system may identify a Soft Clash or Clearance Clash.
The exact terminology can vary between project teams and software workflows, but the underlying issue is insufficient required space.
What Is a Clearance Zone in BIM?
A clearance zone is a defined space around an element that should remain free from other building components.
Clearance zones may be required for:
- equipment maintenance
- installation
- insulation
- access
- movement
- ventilation
- safety
- operation
- component replacement
Clearance zones can be represented within BIM models or applied through clash-detection rules.
When another element enters this defined zone, it may generate a Soft Clash.
MEP Soft Clashes
Soft clashes are particularly important in MEP coordination because building services frequently share limited space.
Common examples include:
Mechanical
- ductwork too close to equipment access panels
- insufficient space around HVAC units
- inadequate insulation clearance
Electrical
- cable trays blocking electrical-panel access
- services entering required electrical working zones
- insufficient space around electrical equipment
Plumbing
- pipes blocking valve access
- insufficient space for pipe insulation
- plumbing services interfering with equipment maintenance areas
Fire Protection
- services interfering with sprinkler coverage
- insufficient access to fire-protection equipment
- conflicts around maintenance or operational zones
How Are Soft Clashes Resolved?
After a Soft Clash is identified, the coordination team reviews the required clearance and determines whether a model change is necessary.
Possible resolution methods include:
- moving an element
- adjusting elevation
- adding an offset
- changing routing
- modifying equipment placement
- changing service spacing
- redesigning a small section of the system
- reviewing the clearance requirement where appropriate
The objective is to create enough space for the required function without introducing new coordination problems.
After modification, the model should be checked again.
Can Soft Clashes Be Automatically Resolved?
Some Soft Clashes may be suitable for automated or semi-automated resolution when the system can understand:
- required clearance
- movable elements
- system connectivity
- available routing space
- surrounding geometry
- acceptable movement
- project constraints
However, not every Soft Clash can be resolved automatically.
For example, maintenance requirements, equipment-access rules, design preferences, or project-specific safety requirements may require engineering judgement.
Therefore, automation should work within clearly defined project constraints and be followed by engineering review where required.
Why Are Soft Clashes Important?
Soft clashes are important because a model can appear physically clash-free while still containing coordination problems.
Identifying Soft Clashes can help teams:
- maintain required service clearances
- preserve equipment accessibility
- improve installation feasibility
- support maintenance access
- reduce site coordination problems
- improve MEP constructability
- identify issues before construction
- improve multidisciplinary coordination
A clash-free model should therefore consider both physical intersections and required clearances.
Soft Clashes in BIM Coordination
Soft Clash detection forms part of the broader BIM coordination process.
A simplified workflow is:
Model Creation → BIM Coordination → Clash Detection → Soft Clash Identification → Review → Clash Resolution → Verification
The key distinction is:
Clash Detection identifies the clearance problem.
BIM Clash Resolution addresses how the affected elements should be modified.
How VAVETEK AI Relates to Soft Clash Workflows
VAVETEK AI develops BIM technologies supporting different stages of model coordination.
KlashBIM supports BIM clash-detection workflows by identifying and organizing model conflicts.
Where supported clashes require modification, HUBAROC provides engineer-controlled resolution workflows, while BAMROC supports automatic resolution of eligible clash scenarios.
The broader coordination process can be understood as:
Detect → Review → Resolve → Verify
Whether a specific Soft Clash can be automatically resolved depends on the geometry, clearance requirements, engineering constraints, and supported workflow.
Frequently Asked Questions
What is a Soft Clash in BIM?
A Soft Clash is a BIM coordination conflict where two elements may not physically intersect but violate a required clearance, access, tolerance, or maintenance distance.
What is an example of a Soft Clash?
An example is a pipe passing too close to HVAC equipment and blocking the space required to open a maintenance panel.
What is the difference between a Soft Clash and a Hard Clash?
A Hard Clash involves direct physical intersection between elements, while a Soft Clash occurs when the required clearance between elements is insufficient.
Is a Soft Clash the same as a Clearance Clash?
Soft Clash and Clearance Clash are commonly used to describe conflicts where required spatial clearance is violated even though the elements may not physically intersect.
How are Soft Clashes detected?
Soft Clashes are detected by comparing model elements against predefined clearance or tolerance requirements during BIM clash detection.
Why are Soft Clashes important in MEP coordination?
MEP systems often share limited ceiling, riser, plant-room, and service-space areas. Soft-clash detection helps preserve installation, operation, insulation, and maintenance clearances.
Can Soft Clashes be resolved automatically?
Some Soft Clashes may be suitable for automated or semi-automated resolution where clearance requirements and allowable model changes are clearly defined. Complex cases may require engineer review.
Are all Soft Clash results genuine problems?
No. Some detected clearance violations may be acceptable depending on project requirements, modelling rules, or approved conditions. Clash results should therefore be reviewed before modification.
What happens after a Soft Clash is detected?
The coordination team reviews the required clearance, determines whether the condition is acceptable, modifies the relevant elements if necessary, and reruns clash detection to verify the result.