A Practical BIM Clash Detection Workflow (Free, No Desktop Coordination Tool)

A repeatable end-to-end process for finding, filtering, assigning, and resolving clashes between disciplines — using free online tools only.

Clash detection in one tool is a click. Clash detection as a workflow — weekly, across disciplines, with tracked issues and resolution — is a process that many firms still bolt onto a desktop coordination licence costing thousands per seat. Here is how to run the same workflow with free online tools.

What counts as a clash

Clashes come in three flavours:

Hard clashes — two solid elements physically overlap. A pipe inside a beam. Two ducts sharing the same space. These are the most common and easiest to detect.
Clearance clashes — elements do not overlap, but they sit closer than a required minimum distance. A pipe 2 cm from a wall where the maintenance code requires 15 cm clearance.
Workflow clashes — sequencing issues that are not geometric at all (for example, "this conduit cannot be installed before this beam"). These typically need 4D tools and are beyond pure geometric clash detection.

BIMCamel's Clash Detection tool handles hard clashes and configurable clearance clashes. Workflow clashes are a human-review step on top.

The weekly clash cycle

A predictable rhythm beats clever ad-hoc checks. Here is a workflow that fits on a one-page BEP:

Monday morning — model receipt.

Each discipline drops their latest IFC into a shared folder. Tag with discipline (ARC, STR, MEP) and revision date.

Monday afternoon — pre-flight checks.

Before running any clash detection, run Model Health Check on every incoming file. Rejecting a bad file on Monday costs ten minutes; running the full federation on a bad file and realising Wednesday costs half a week. Specifically:

Fix coordinates if needed (Fix IFC Coordinates with "Preserve georeferencing" on each discipline file so they federate cleanly).
Confirm unit systems match.
Confirm schema versions match or are compatible.

Tuesday — federate and clash.

Run Merge Files on the three discipline files. The output is a single federated IFC.
Run Clash Detection on the federated model. Configure element group pairs:
- STR vs MEP (high priority — hard clashes expensive to fix later)
- ARC vs MEP (medium priority)
- STR vs ARC (low priority if both were coordinated internally, medium otherwise)
Export the clash report to CSV or Excel.

Wednesday — triage.

Not every clash is worth fixing. Filter the report:

Group by severity (volume of overlap, element importance).
Ignore known-acceptable clashes (e.g. a conduit passing through a stud wall that has an explicit sleeve).
Assign remaining clashes to a discipline owner.

Thursday — resolution.

Discipline owners work on their assigned clashes in their authoring tool. They do NOT need BIMCamel for this — clash resolution is authoring work.

Friday — verification.

Request re-exported models from each discipline. Re-run the Tuesday cycle on the updated files. Confirm that resolved clashes are gone and no new ones have appeared as a side effect.

Turning this into a saved pipeline

The Tuesday + Friday steps are mechanical. Save a pipeline:

Merge the three named input files.
Run Clash Detection with a preset element-group configuration.
Save a snapshot of the federated model.
Export the clash report.

One-click federation + clash check every cycle, no manual configuration.

Clash detection vs IDS validation

These are often confused but do different things:

Clash detection finds geometric overlaps between elements.
IDS validation finds data gaps (missing properties, wrong classifications).

A well-coordinated project runs both. Geometric clashes hurt construction; data gaps hurt handover. The two checks complement each other.

Reading the clash report

Every clash entry carries:

Two element GUIDs (the clashing pair).
Element types and names (so "IfcWall-EXT-042 clashes with IfcDuct-MEP-117").
Overlap volume or clearance distance.
Storey assignment (which floor is affected).

Sort by storey to batch clashes for per-floor review. Sort by volume to triage the biggest clashes first.

Common clash-report noise

Structural/architectural overlaps at walls and columns. Often the architect and structural engineer modelled the same physical element twice. Use Compare IFC to spot which discipline owns each element, then filter these out.
MEP penetrations through walls. If penetrations are intentional (designed sleeves), tag them as accepted in the report and filter them out of future cycles.
Coordinate system drift. If "every element clashes with every element," you almost certainly have a coordinate mismatch. Go back to Fix IFC Coordinates.

Clash detection is not glamorous. But a team that runs it weekly ships projects with far fewer field change orders than one that does not. A free toolkit makes that discipline affordable for any team.