BIM Clash Detection: Understanding the Process, Advantages and Best Practices

BIM clash detection and resolution enabled by interdisciplinary BIM coordination reduces costly rework, project delays and budget overruns. The clash detection process in the pre-construction stage is supported by Revit® and Navisworks®.

Coordinated BIM models ensure perfect synchronization between architectural, structural and MEPF disciplines. So, whether you are a building engineering consultant, architectural firm or a contractor, if you have leveraged the power of BIM coordination, you can be sure of zero unwanted surprises springing up during construction stage. All conflicts and clashes are addressed by systematic BIM clash detection and resolution using Revit and Navisworks, right at the pre-construction stage.

In this article, we talk at length about what is clash detection, the need for clash detection, the types and benefits of clash detection etc.

What is Clash Detection in Building Information Modeling (BIM)?

Clash detection refers to identifying and resolving conflicts between different trades in a building construction project.

The process involves the following steps:

• 3D Revit Models: Models from all building trades (Architecture, Structure, MEPF) are combined, originating from their respective starting points, to create a single federated 3D BIM model.
• Integration: During the integration, clashes are detected between various building components or elements.
• Highlighting and Sharing: Identified clashes are highlighted and shared with the respective design consultants for resolution.
• Resolution and Re-checking: Once the clashes are resolved, the updated designs are incorporated into the main model, and clash detection is run again to ensure overall coordination with surrounding elements.
• Final Coordination at BIM Level 2: The final coordination is performed at BIM Level 2. For instance, a beam may interfere with an air-conditioning unit, a pipe with a duct, or there could be insufficient beam tolerances in the 3D model.

What Causes Clashes in BIM Models?

Clashes occur when architectural, structural, and MEPF models are integrated into a single federated 3D model, revealing conflicts between the individual models. The process begins with the creation of a 3D BIM model using Revit from drawings, images, or other PDF files, starting with the architectural set. Structural engineers then create their 3D model, aligning it with the architectural layout.

HVAC engineers, plumbing designers, electrical engineers, and fire protection specialists each develop their own 3D models to integrate with the architectural and structural layouts. Each discipline’s 3D BIM model contains its own dataset, including documents, project files, geometric data, and other vital information about the built asset.

The challenge is to combine these individual 3D models into a single, coordinated 3D model to detect clashes. Simply put, clashes are identified in a 3D model when the spatial coordination of the individual models reveals overlaps and conflicts.

There are several reasons why clashes may occur in BIM models. Some of the common causes include:

• Use of an incorrect or insufficient level of detail (LOD)
• Design uncertainties or failures in following design rules
• Inaccurate models due to time constraints
• 3D model objects exceeding required clearance values
• Siloed design workflows and high design complexities
• Using 2D models instead of 3D BIM models
• Design errors resulting from a lack of expertise

To prevent clashes, AEC stakeholders can implement several strategies, such as:

• Integrating BIM with traditional workflows
• Coordinating engineering, construction, and procurement efforts
• Enhancing communication and collaboration among designers within a shared working space
• Adopting design coordination within a Common Data Environment (CDE)

Issues in Clash Detection with Legacy Tools

Traditional 2D CAD drawings lack the accuracy, data integrity, and visualization needed for efficient fabrication and installation. These error-prone 2D drawings often require extensive manual intervention, leading to data silos, fragmentation, data loss, and outdated file sets. As a result, projects face rework, cost overruns, and delays.

Some of the challenges stakeholders encounter when using legacy tools for clash detection include:

• Inaccuracies in design engineering and documentation
• Increased number of design iterations during the design and pre-construction phases
• Inefficient coordination and collaboration among stakeholders
• Reduced project efficiency due to erroneous 2D deliverables
• Higher material costs caused by inaccurate fabrication and onsite waste
• Increased onsite risks leading to delays and cost overruns
• Limited visualization of the building using only 2D drawings

When is BIM Clash Detection Performed?

BIM clash detection is typically conducted during the pre-construction or design phase for various disciplines, using tools like Revit and other visualization software such as Navisworks. Identifying and resolving clashes early in the design process minimizes rework, facilitates smoother planning, and ensures seamless construction. Accurate Bills of Quantities (BOQs) and Bills of Materials (BOMs) contribute to error-free installation and fabrication, ultimately saving both time and costs.

Using Navisworks for clash detection enhances collaboration across multiple trades and ensures more efficient and effective project outcomes.

Benefits of BIM Clash Detection for AEC Stakeholders

BIM-based tools and technology offer a host of advantages to AEC stakeholders. Adopting BIM can help architects, engineers and consultants to save up to 70% of construction rework caused by design and engineering errors. Here are some major benefits of BIM clash detection:

A clash-free 3D model with 360-degree visualization offers complete clarity for the building project. Field personnel can use AR/VR technology to walk through the model, gaining insights into the position, geometry, description, and other necessary information to operate efficiently.

Types of Clashes in BIM

There are several types of clashes that can occur in architectural, structural, and MEP layouts and designs. BIM helps identify and resolve these clashes, leading to error-free construction. The main types of BIM clashes are:

• Hard clashes: These occur when two building elements, components, or members occupy the same physical space. For example, columns interfering with walls or pipes running through beams create hard clashes. These are difficult to resolve and can be costly if discovered later during construction. Hard clashes can typically be addressed based on geometry or design rules during the planning phase.
• Soft clashes: A soft clash happens when building elements do not meet the required geometric or spatial tolerances. For instance, improper clearance for an air-conditioning unit may cause issues with access, maintenance, or safety. Relevant standards and regulations set within software like Navisworks can help identify these clashes in advance.
• Workflow clashes: Also known as 4D clashes, these occur when there is a conflict in the project timeline, such as between contractor scheduling, equipment, and material delivery. An example of this would be if the delivery of a spare part is not aligned with the scheduled HVAC maintenance.

How are Clashes Detected and Resolved?

The clash detection process begins by using the master 3D model in Navisworks or similar software. Below is a flowchart that outlines the entire clash detection process within a BIM framework, making it easier to understand.

Best Practices for BIM Clash Detection Using Navisworks

Even a compliant building design may have issues that lead to inefficiencies. Architects, engineers and contractors use BIM clash detection procedures to generate clash reports, identify potential conflicts, and resolve them before the design review and final approval.

The Growing Importance of BIM-Based Clash Detection in the AEC Industry

BIM-based clash detection plays a crucial role in modern construction. As global projects become increasingly complex across Architecture, Structural, and MEPF disciplines, the need to complete projects on time and within budget makes clash detection essential for improving coordination, and ensuring accurate BOMs, BOQs, and GFC drawings.

The use of a Common Data Environment (CDE) and clash-free generative design is gaining popularity in complex projects. As technology evolves, the adoption of advanced BIM tools with coordinated, interference-free 3D models will become standard practice in the industry.

Conclusion

BIM-based clash detection and resolution will remain a critical process during the pre-construction phase for multiple stakeholders. Having a coordinated, multi-disciplinary, and clash-free 3D model readily available ensures significant cost and time savings in the digital space. Eliminating clashes early in the design stage using automation scripts will greatly reduce design, procurement, fabrication, and installation time and costs.

As the world shifts toward greater sustainability and more efficient use of energy and resources, clash detection and the pre-construction resolution of clashes will become mandatory rather than optional.