BIM Clash Detection: Tests, Triage and Verified Resolution

BIM clash detection checks selected model geometry for conflicts under defined rules. It can help teams find interfaces that need attention, but a detected result is not yet a resolved design issue.

Use testing as part of a coordination workflow: check inputs, select tests, review results, assign decisions and verify updates. The MEP coordination guide explains the surrounding responsibilities and deliverables.

Understand what each test checks

Autodesk's Navisworks documentation distinguishes hard intersections, clearance checks and duplicate geometry. A clearance test checks geometry within a specified distance; choose the distance for the interface you need to review. Navisworks test options.

Software terminology can vary. State the test type, selected model sets and tolerance in the coordination record so another reviewer can understand what was checked.

Check inputs before interpreting the count

Verify source revisions, coordinates, units and included disciplines. Note missing submissions. Duplicate linked geometry or an outdated model can produce results that do not represent the current design.

A report with fewer results may reflect a reduced model scope rather than improved coordination. Keep test definitions and source records when comparing review cycles.

Build a test matrix

For each interface, define the two model sets, the question, test type, tolerance and responsible reviewer. Prioritize the interfaces needed for the next work-package decision.

Illustrative example: a structural-versus-ductwork test may identify intersections between ducts and beams. A separate access review may be needed for equipment maintenance. Running the first test does not demonstrate that the second concern has been addressed.

Avoid assuming one tolerance works for all systems. The team should agree the relevant requirements and any modeled access or insulation allowances.

Turn results into issues

Review whether several results refer to the same underlying decision. Group them when that helps the team act, but preserve the affected locations and elements.

A useful issue includes:

• Identifier and location.
• Affected models, revisions and elements.
• Description of the question.
• Responsible person and next action.
• Due date and status.
• Evidence needed to verify the change.

Resolve and retest

Discuss alternatives with the people responsible for the design. The coordinator can organize the information and follow-up, but the assigned designers or trade participants must make the relevant technical decisions.

After revised models arrive, check the affected interface and any consequential changes. Record the source revision used for verification. If the issue remains unresolved or the new information is incomplete, retain that status rather than closing it to improve a dashboard.

What should the report communicate?

Summarize tested scope, missing inputs, decision priorities, open issues and verified changes. Distinguish a test result from a tracked issue and a tracked issue from an accepted release.

If a report will support construction planning, identify which project roles determine whether the information is suitable for use. A clash-detection report is not a blanket construction approval.

Frequently asked questions

Does “clash-free” mean error-free?

No. Tests cover selected geometry under selected rules. Unmodeled conditions, incomplete information, design calculations and field verification remain outside that result unless addressed separately.

Can we automate the whole process?

Tools can automate parts of testing and reporting. Interpreting the result, selecting a design response and confirming responsibilities still require the project team's judgment.

What should we request from a provider?

Request the test scope, input checks, issue workflow, review frequency and closure evidence, alongside the output formats. The BIM coordination service and proposal checklist explain how to scope that work.