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What is clash detection?

Clash detection is the process of identifying conflicts between elements within one or more BIM models before those conflicts create problems during construction.

In architecture, engineering, and construction, multiple disciplines contribute to the design of the same project. Architectural, structural, mechanical, electrical, and plumbing systems must all fit within a shared physical space.

Clash detection allows project teams to combine these models and identify where building elements intersect, violate required clearances, or create other coordination problems.

Each discipline usually models in its own software and at its own pace, so conflicts can go unnoticed until the models are brought together into a federated model and tested against each other.

For example, clash detection might identify an HVAC duct passing through a structural beam, pipework conflicting with electrical services, or equipment without enough clearance for installation or maintenance.

In practice, BIM connects project models, information standards and coordination workflows across disciplines and project stages.

Why is clash detection important?

Design conflicts become more difficult and expensive to resolve once construction has started.

A late clash can mean stopping work, re-fabricating components, or issuing a request for information (RFI) while crews wait for an answer. Finding the same conflict in the model costs a fraction of that effort.

Clash detection allows BIM/VDC teams to identify many of these problems digitally during design and preconstruction, when changes are generally easier to coordinate.

Effective clash detection can help project teams:

Identify multidisciplinary design conflicts earlier
Reduce construction rework
Improve coordination between disciplines and trades
Prevent avoidable issues from reaching the field
Reduce delays associated with design conflicts
Prioritise coordination issues before construction
Improve accountability for issue resolution
Give teams greater visibility of outstanding coordination problems

The value comes from resolving clashes, not from counting them, which is why detection works best as part of a wider coordination process.

What are the different types of clashes?

Clashes are commonly divided into three categories:

Type	What it means	Example
Hard clash	Two physical elements occupy the same space.	A ventilation duct passes through a structural beam.
Soft clash	An element violates a required clearance, tolerance or spatial requirement.	Mechanical equipment does not have enough space around it for maintenance.
Workflow or 4D clash	Construction activities, resources, schedules or work areas conflict.	Two trades are scheduled to work in the same area at the same time.

Not every detected clash represents a genuine construction problem. A single root cause, such as one misplaced riser, can also produce dozens of duplicate results. BIM/VDC teams typically review clash results to identify actionable issues and remove duplicates, acceptable conditions, and false positives.

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How does clash detection work?

A typical BIM clash detection workflow includes:

Federate models

Bring architectural, structural, MEP, and other relevant discipline models together for multidisciplinary coordination. Each discipline keeps ownership of its own model while the team gets one combined view to test.

Define clash rules

Determine which systems or model elements should be checked against each other and establish appropriate tolerances. Rules usually pair systems likely to conflict, such as ducts against structure, and tolerances stop minor overlaps from flooding the results.

Run clash detection

Analyse the models to identify physical intersections, clearance violations, and other potential conflicts. Results are often grouped by location or system so reviewers can work through related clashes together.

Review and prioritise

Validate detected clashes, remove false positives and duplicates, and determine which conflicts require action. Reviewers decide which clashes need action now, which can wait, and which are acceptable as modelled.

Assign and resolve

Turn relevant clashes into coordination issues, assign responsibility, track progress, and verify that the underlying problem has been resolved. A clash is only closed once the updated model has been checked and the conflict no longer appears.

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Clash detection vs clash coordination

Clash detection and clash coordination are closely related, but they are not the same process.

Clash detection identifies potential conflicts within BIM models.

Clash coordination is the broader process of reviewing, prioritising, communicating, assigning, resolving, and verifying those conflicts across project teams.

A clash detection test can generate hundreds or even thousands of results. The objective is therefore not simply to identify as many clashes as possible.

Effective BIM coordination helps teams determine which clashes represent genuine project risks and creates a structured process for resolving them. Put simply, detection tells a team where the problems are, and coordination makes sure someone fixes them.

When should clash detection be performed?

Clash detection should be an ongoing part of the BIM coordination process rather than a single check performed immediately before construction.

Teams may run clash detection as discipline models are developed and updated throughout design and preconstruction. Many teams tie checks to coordination meetings or design milestones, with lighter, more frequent checks in between.

Regular clash reviews allow project teams to identify new conflicts as designs change, track unresolved issues, and verify that previously identified problems have been addressed.

The frequency of clash detection depends on the project's size, complexity, delivery method, and coordination schedule.

How does Revizto support clash detection?

Revizto connects clash detection with the broader BIM coordination and issue management process.

With Revizto Clash Automation, BIM/VDC teams can identify and group clashes, review results in their project context, and turn relevant clashes into trackable issues.

Project teams can then assign responsibility, communicate around issues, monitor their status, and verify resolution within a shared environment.

Because issues stay linked to the model view and the 2D sheet they refer to, anyone on the project can open a problem in context without searching for files. BIM/VDC managers can also see which clashes are open, who owns them and how long they have been outstanding.

This helps move clash detection beyond identifying model conflicts and connects the process directly with the teams responsible for resolving them.

FAQs

Clash detection is the process of identifying conflicts between elements within BIM models before they cause problems during construction. It lets BIM/VDC teams find where ducts, pipes, structure and equipment overlap or break clearance rules while changes are still inexpensive to make.

The three commonly recognised categories are hard clashes (elements occupying the same space), soft clashes (clearance or tolerance violations), and workflow or 4D clashes (conflicts in scheduling or work areas).

A common example is identifying where an HVAC duct intersects a structural beam before either element is installed on site. The team can then reroute the duct or adjust the beam penetration in the model.

Clash detection identifies potential model conflicts. Clash coordination is the broader process of reviewing, prioritising, assigning, resolving, and verifying those conflicts. Detection finds the conflict; coordination makes sure it is fixed and checked.

Clash detection is commonly managed by BIM/VDC managers and coordinators, with architects, engineers, contractors, subcontractors, and other project stakeholders involved in reviewing and resolving identified issues. The coordinator usually leads the process, while each discipline fixes clashes in its own model.

Clash detection software combines discipline models, tests them against rules and lists the conflicts it finds. Tools range from model-checking applications to coordination platforms such as Revizto, which also manage the issues that follow.

A false positive is a reported clash that is not a real problem, such as an acceptable overlap, a duplicate, or a result caused by loose tolerances. Reviewing and filtering them keeps teams focused on genuine risks.