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VDC clash detection and coordination errors are best fixed by validating the models first, then configuring focused checks, reviewing real conflicts with the right people, correcting the responsible authoring model, and verifying the refreshed federation. A clash report is a list of candidates—not proof that every flagged pair is a design problem, or that every important clearance issue has been found.
The reliable approach is a repeatable cycle: use current, aligned models; test the question the team actually needs answered; record each actionable issue with a location, owner, and next step; and rerun the relevant check after a change. That prevents teams from spending time adjusting tolerances to hide a bad export, or closing an issue before its correction appears in the coordinated model.
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First confirm that the right discipline models, versions, and project scope are in the federation. If an expected object is missing, duplicated, or visibly offset, investigate the authoring model, export, or federation before changing clash settings. A tolerance adjustment cannot repair an outdated or misaligned input.
Check the following before reviewing individual results:
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- Model versions: Confirm that each discipline’s submitted model is the intended current version, not an older export left in the coordination set.
- Discipline coverage: Make sure the tested set includes the models relevant to the coordination question. A check between two trades cannot identify a conflict with a third model that was not included.
- Coordinates and scope: Verify that models use the project’s agreed coordinate setup and cover the intended area, level, or package. A displaced model can create misleading results or conceal real overlaps.
- Export and federation: Confirm that the files were produced and compiled as the project expects. The Port Authority of New York and New Jersey’s BIM Standard, for example, assigns discipline leaders responsibility for producing NWC exports and describes compiling them into a master NWF. Those are project-specific procedures, not universal requirements.
- Completeness and validation: Check that the models contain enough of the relevant design to make the test meaningful. A missing route or incomplete system is not evidence that coordination is clear.
The Port Authority BIM Standard and Orange County Sanitation District’s CAD/BIM standards describe coordination roles, model updates, and federation practices for their respective organizations. A Solibri workflow article also cautions that incomplete or unvalidated models and incorrect federation can undermine clash detection. The practical lesson is to diagnose input problems separately from design conflicts and document which one you found.
If a model appears shifted, for example, describe the issue as a suspected alignment or export problem and identify the affected file. Do not report every resulting intersection as a design clash until the input has been checked. Likewise, if the same object appears twice, check whether the model or federation includes repeated geometry before assigning a designer to move it.
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Define the coordination question first, then choose the test type, model selections, and tolerance that fit it. Do not treat one clash setting or tolerance as correct for every discipline pair or project.
Common checks address different questions:
- Hard clash: Does geometry physically intersect—for example, does a duct route pass through a beam?
- Conservative hard clash: Could objects potentially intersect, depending on how the test handles the geometry? This can be useful when a strict overlap test would miss a near-intersection worth reviewing.
- Clearance test: Is the required space around an object preserved? The question may be whether equipment has room for servicing, not whether two modeled objects occupy the same point.
- Duplicate check: Is geometry represented more than once, creating repeated elements or misleading results?
Autodesk’s clash detection setup guidance describes these test types and the use of selected item surfaces, centerlines, or points, as well as tolerances and clearances. Choose selections that reflect the question. A test intended to find duct-to-structure intersections should not be expanded indiscriminately to unrelated model pairs if the result is a large, difficult-to-review list.
Set a tolerance only to serve a stated coordination purpose—for example, to ignore negligible results or to check a specified required distance. The actual clearance must come from the project’s design criteria, applicable requirements, or an approved decision. The cited setup guidance explains how a tolerance functions as a test setting; it does not establish a universal value suitable for all projects.
For each recurring test, record the included model sets, test type, selection method, and tolerance or clearance. This makes a result easier to reproduce and helps reviewers distinguish a changed design from a changed test setup. If a result count changes sharply between coordination cycles, check whether the models or settings changed before concluding that the design improved or worsened.
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What is the difference between a hard clash and a soft clash?
A hard clash is a physical intersection; a soft clash is a conflict involving required space, tolerance, access, or operation, even when the modeled objects do not physically overlap. Both can matter to design and construction, but they need different checks and decisions.
The GSA BIM Guide 07 describes hard clashes as objects occupying the same physical space and soft clashes as interference with clearances, tolerances, or access. For instance, equipment may not intersect a wall, yet a nearby door or another system could prevent the equipment from being accessed or maintained.
That distinction affects what the team should do next. A geometry-intersection test may identify the first condition, while the second may require a clearance test, a modeled clearance object, or a review by someone who understands the access or maintenance requirement. Orange County Sanitation District’s standards call for team review of detected conflicts and maintenance review using access requirements or clearance objects. An automated flag is a candidate to evaluate; the team determines whether it represents a real design, construction, operational, or maintenance issue.
Do not dismiss a result simply because it is not a hard clash. Conversely, do not label every proximity as an actionable soft clash without checking the required clearance and project criteria. State what is affected and why it matters—for example, “service access to this equipment is obstructed”—rather than relying on a generic clash label.
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Review results for project significance, group related findings, and assign a clear action to each issue that requires a response. Raw clash counts do not tell the team which condition is important, who can resolve it, or whether a design decision is needed.
Prioritize issues that affect major systems, constructability, required access, or coordination across disciplines. Then check whether each result is real in the current model and whether the test reflects a project requirement. Nearby results may describe one underlying routing problem; grouping them can make the discussion more useful, provided the issue record still identifies the affected locations and elements.
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An actionable record should give the recipient enough information to find and decide the issue without reconstructing the entire test. Orange County Sanitation District’s standards identify a reporter, specific 3D location, image or description, and assigned resolver as minimum issue attributes. The Port Authority standard calls for a report listing reviewed clashes and issues and the course of action agreed. Use those as practical examples, while following the project’s own BIM execution plan and issue process.
Include, as appropriate:
- a specific model location or viewpoint;
- the affected elements or discipline models;
- a short description of the observed condition and its consequence;
- an image or saved view that helps the recipient locate it;
- the person or discipline expected to respond;
- the current status and next action; and
- the decision or requirement behind a requested clearance or design change.
If the proposed fix affects another discipline, design intent, or project requirements, route it to the responsible design decision-maker. Do not make an undocumented geometry change merely to clear a clash. There is no single decision hierarchy that applies to every project; use the roles and approval path established in the project BIM execution plan.
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How do you fix a clash in the authoring model?
Make an approved correction in the model owned by the responsible discipline, then publish a new coordination export and refresh the federation. Avoid treating a temporary move in the federated review model as a completed design fix.
- Open the issue in context. Use the clash result, element information, and saved viewpoint to locate the affected object in its authoring model. Confirm that the issue still exists in the current model version.
- Confirm ownership and design intent. Identify which discipline owns the element and whether the change is within that team’s authority. If a reroute or relocation changes design intent, affects another system, or needs approval, obtain the appropriate decision before editing.
- Make the correction in the responsible model. The appropriate fix might involve rerouting, repositioning, or revising an element, but the correct action depends on project requirements and design decisions. Record the agreed resolution rather than guessing at a geometry change solely to remove a flag.
- Export the corrected model. In the documented Navisworks-to-Revit workflow, Autodesk describes locating the element in Revit, making the change, and exporting a new NWC.
- Replace or refresh the coordinated input. Replace the older referenced file as required by the project setup, then refresh the model in Navisworks so the federation contains the correction. Confirm that the new version—not the old export—is loaded.
- Recheck the issue. Rerun or refresh the relevant test, inspect the location and viewpoint, and check whether the correction created a new conflict nearby. The last check is a prudent validation step: a rerouted element can resolve one intersection while affecting another.
- Update the issue record. Change status only after the updated model has been reviewed. Preserve any outstanding decision or follow-up rather than marking an unresolved condition complete.
This sequence follows Autodesk’s documented workflow for resolving clashes between Navisworks and Revit. Autodesk’s Navisworks 2026 documentation for working with coordination issues also describes creating issues from clash test results and synchronizing issue data between Navisworks and Model Coordination. The exact workflow depends on the project’s tools, file references, and approved issue-management process.
Why do clash issues keep coming back?
Recurring issues often point to a coordination process problem, not just a difficult geometry problem. Stale or incomplete inputs, unclear ownership, inconsistent tests, and unresolved decisions can all make a clash reappear or remain open from one cycle to the next.
Use the pattern of recurrence to narrow the cause:
- The same issue reappears after a reported fix: Check whether the corrected export was published, included in the federation, and refreshed. Verify the version and the affected element rather than assuming the authoring change was lost.
- Many new results appear at once: Check whether model scope, federation, coordinates, selection sets, or tolerance changed. A larger result list may reflect changed inputs or test configuration, not necessarily a sudden wave of design conflicts.
- Issues stay open without progress: Look for missing owners, unclear requests, or decisions that require a design lead or client. A clash report alone does not create authority to change the design.
- Geometry checks pass but access problems emerge later: Add or review clearance and maintenance requirements with the appropriate stakeholders. A physical-intersection test cannot answer every operations question.
- The team closes issues inconsistently: Agree what evidence is needed before an issue is considered resolved, such as an updated model, a refreshed test, and a reviewed viewpoint.
A Solibri workflow article identifies late one-time checks, large unprioritized result volumes, and missing issue ownership as failure modes that can prevent detected problems from being resolved. It also quotes practitioners on the value of embedding clash detection in regular coordination and issue-tracking cycles. These are practitioner observations, not standards requirements or quantified findings.
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How often should VDC teams run coordination checks?
Set a project-specific cadence in the BIM execution plan or equivalent coordination procedure, then align model submissions, review sessions, and issue follow-up to that schedule. The cited standards provide examples of planned and regular updates, not one universal frequency for every project.
Orange County Sanitation District’s manual recommends establishing a project timeline, enabling regular model updates, assigning and reviewing clashes with design authors, and involving maintenance personnel in access review. The Port Authority standard places cross-discipline coordination frequency in the project BIM execution plan and describes distributing a federated NWD with saved viewpoints and a report after sessions. Those practices illustrate a repeatable process; the appropriate interval depends on the project’s agreed schedule and scope.
A useful cycle is:
- Publish current discipline models and confirm their versions.
- Federate the agreed model set and validate alignment and scope.
- Run the scoped checks with documented settings.
- Review, filter, group, and assign actionable issues.
- Make approved corrections in their authoring models.
- Refresh the federation, verify fixes, and carry unresolved decisions into the next review or formal approval process.
This cycle makes model readiness and issue closure part of coordination rather than leaving clash detection until a late, one-time review. It also gives the team a way to see whether repeated results stem from an unresolved design question, an input problem, or a missed handoff.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How should you choose a coordination tool?
Choose a toolset that fits the project’s required model formats, test controls, issue workflow, reporting needs, and client standards. The available guidance identifies several coordination approaches but does not establish a neutral current software ranking or current pricing.
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Before committing to a workflow, check whether it can:
- work with the authoring and exchange formats required by the project;
- define clash types, selections, tolerances, grouping, and filtering appropriate to the checks;
- assign issues, track status, and synchronize information with authoring tools or the common data environment when required;
- preserve useful viewpoints, reports, and an audit trail of resolution;
- support clearance, constructability, and maintenance reviews, not only geometric intersections; and
- meet the client’s standards and the project BIM execution plan.
Autodesk documentation supports the Navisworks/Revit correction sequence and issue synchronization described above; the Solibri workflow article discusses setting up recurring clash-detection processes. The Commonwealth of Massachusetts BIM Guidelines provide another public-sector example of design coordination guidance. These references help explain different process elements; they are not a substitute for confirming compatibility and requirements on a specific project.
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What should a coordination report contain?
A useful report communicates what was reviewed, what needs action, and what was decided—not just how many clashes the software returned. Include enough context for the responsible person to locate the condition and for the project team to track the resolution.
At minimum, identify the model set or versions reviewed, relevant test or issue identifiers, actionable findings, their locations or viewpoints, the assigned resolver, and the agreed action or open decision. Where a session leads to a different design direction, record that course of action and who needs to carry it forward. The Port Authority standard describes a report listing reviewed clashes and issues and the agreed course of action; Orange County Sanitation District’s standards specify issue details such as reporter, location, image or description, and resolver.
Keep the distinction between the report and the issue record clear. The report summarizes the coordination review; individual issue records carry the details needed to resolve and verify particular conditions. If an issue remains open because a decision is pending, say so rather than implying that a clash count or meeting discussion has closed it.
What are the most common mistakes to avoid?
The most costly coordination mistakes are usually avoidable process errors: checking the wrong inputs, using an unfocused test, treating every flag as a design defect, or closing an issue without verifying the updated model.
- Changing tolerances to suppress noise before checking alignment. Validate coordinates, exports, scope, and federation first.
- Using one test for every question. Physical intersections, potential intersections, clearance, and duplicate geometry require different checks.
- Assuming proximity is automatically a clash—or never a clash. Evaluate the project requirement, access need, and operational consequence.
- Sending a result without context or an owner. Provide a specific location, image or description, responsible resolver, and next action.
- Changing geometry without approval. Route design-impacting decisions through the project’s defined authority and record the agreed resolution.
- Refreshing the wrong file or not refreshing at all. Confirm the corrected export is the one loaded in the federation.
- Closing an issue based only on a message that a fix was made. Review the current model and repeat the relevant test before changing the issue status.
- Running checks only once or too late. Plan recurring model updates and review cycles appropriate to the project.
The central rule is straightforward: a detected clash becomes a resolved coordination issue only when the responsible change is approved, represented in the current coordinated model, and verified against the relevant requirement.
Frequently Asked Questions
Can clash detection find every coordination problem in a VDC model?
No. Automated checks evaluate modeled geometry and the test rules selected, so they cannot establish that an omitted system is coordinated or that every operational requirement has been represented. Design review, constructability input, and maintenance or access review may identify concerns that a particular automated test does not cover.
Should I change the design or the clash tolerance when two objects are close?
Determine whether the project requires a minimum distance and whether the test is intended to check that distance. If the models or coordinates are wrong, fix those inputs; if the clearance is a genuine design requirement, route the decision to the responsible design authority rather than using tolerance settings to make the result disappear.
What does a clash report mean if it contains thousands of results?
It means the configured test returned many candidates, not that the project has that many distinct, actionable design defects. Validate the model set and settings, then filter and group results for review so the team can separate repeated or expected findings from issues that need a decision.
Do coordination issue statuses update automatically when a model changes?
A model refresh and an issue-status change are separate actions unless the project’s specific software workflow links them. Autodesk’s Navisworks 2026 documentation describes issue creation and data synchronization, but teams should still confirm their configured process and verify the updated model before treating a finding as resolved.
