How to Catch Design Conflicts Before Construction Starts: A Clash Detection Workflow Guide

What Clash Detection Actually Prevents

Clash detection is supposed to prevent install-time collisions: duct through a beam, cable tray through a damper, a rooftop unit with no structural pad, a door that cannot swing past a panel. Those are MEP-to-structure, MEP-to-MEP, and architecture-to-MEP conflicts. When they survive into the field, the crew stops, writes an RFI, and waits. The work around the conflict slips even if the rest of the floor is ready.

The cost is rework plus idle time plus the RFI itself. Navigant's widely cited estimate puts average RFI processing around $1,080. The Construction Industry Institute 1-10-100 rule is the usual frame for timing: a change that costs one unit in design costs about ten during construction and about one hundred after occupancy. Those are industry averages, not a forecast for your job. They explain why general contractor teams spend money on coordination before mobilization.

What clash detection does not prevent, by itself, is a bad process. A 4,000-item Navisworks report that nobody grouped is theater. A PDF overlay that one engineer ran on architecture only is a sample, not a review. The workflow below is how you keep the tool from becoming a PDF of noise.

Traditional Clash Detection Workflows

The standard 3D workflow looks like this. Each discipline exports a model. A BIM coordinator federates those files in Navisworks or a cloud clash space in Autodesk Construction Cloud. Clash Detective (or the cloud equivalent) tests geometry. The coordinator groups results, assigns issues, and runs a meeting. Trades update models. The federation runs again until the residual list is acceptable.

That workflow fails in three predictable places. First, it requires a full BIM model from every trade that can create a conflict. Many renovations, public jobs, and smaller commercial packages never get that. Second, it misses issues that only appear when someone cross-references a 2D sheet and a specification: a plenum depth in Division 23 that the RCP cannot hold, a rated penetration with no detail, a shop drawing issued after the last federation. Third, it bottlenecks on the coordinator. One person owns the clash report. Everyone else waits for the next meeting.

A fourth gap shows up on fast-track work. The model is a week behind the last addendum. The superintendent already printed the addendum. Clash Detective is testing last week's solids against this week's hangers. Freeze dates exist to stop that, and they only work if someone enforces them.

None of that makes BIM clash detection optional on a modeled job. It means the Navisworks pass is necessary and incomplete. The drawing set still goes to the field. Someone still has to read it. See AI vs BIM clash detection and 2D vs 3D clash detection for the method split.

Where AI Drawing Review Fits In

AI drawing review inserts before or beside the BIM meeting, on the issued 2D set. The job is to read every sheet and the project manual, then hand a reviewer a list of likely conflicts. The reviewer still decides what is real. The software does not replace the BIM coordinator on a federated job.

Helonic is the worked example. Upload or pull a 2D PDF package, including from Procore or Autodesk Construction Cloud. The platform flags coordination conflicts across disciplines, spec-versus-drawing discrepancies, and code issues, each with a sheet location. That is the overlay pass a project engineer already does, run across the full set instead of a sample. It does not federate Revit models or replace Clash Detective.

Use Helonic when the source of truth is PDF, when a trade never modeled, or when shop drawings arrive after model coordination closed. Keep Navisworks or ACC clash spaces when the model exists. For a product-by-product view, use the 2026 clash detection software guide.

A Practical Clash Detection Checklist

Run this sequence on every issued package. It does not require Helonic, Navisworks, or any other named tool.

1. Freeze the package you are reviewing. Write down the sheet index, model export dates, and specification revision. If the BIM coordinator and the precon reviewer are looking at different packages, they will argue about clashes that are just version drift.
2. Federate models when they exist. Run hard, soft, and clearance tests in whatever BIM tool the project already uses. Group duplicates. Ignore obvious false hits (insulation vs insulation, known temporary objects). This step is empty on jobs with no model. That is fine. Do not invent a federation requirement for a PDF project.
3. Cross-check the 2D set and the specs. Overlay or compare architectural, structural, and MEP sheets. Check ceiling heights against duct depth. Check equipment pads against structural. Check the spec for clearances the drawing never dimensioned. This is the pass that catches shop drawings and consultant PDFs.
4. Classify before anyone writes an RFI. Sort each finding: document fix (the set can be corrected), model fix (the federation is wrong), RFI (the documents do not give one buildable answer), or no action. Opening an RFI for every overlay mark floods the log.
5. Verify the next issue. When the designer or modeler issues a response, reopen the log. Confirm the beam moved, the spec changed, or the shop drawing was revised. Verbal promises do not close clashes. The next package does.

Name one owner for the clash log. Publish the frozen package date on every comment. And refuse to call the job coordinated because the model report is green if the shop drawings have not been checked. Related reading: how to find clashes in 2D drawings and Helonic clash detection.

Frequently Asked Questions