The Clashes BIM Does Not Catch

Clash detection earns its money on the big trades. Duct against steel, sprinkler against structure, conduit against beam — resolved in the model, weeks before anyone is on a lift.

Then low voltage arrives. And the problems it brings are usually not in the clash model at all, because a camera is a symbol on a drawing rather than geometry, and the cable feeding it is a line the design tool drew without asking what else is in that pathway.

The conflicts that show up at trim-out

Three kinds, and only the first is familiar.

Separation and congestion. Low-voltage cable run too close to power, a pathway already at fill, an adjacency that is not allowed. These have codified answers — NEC 300.3, NEC 800.133, TIA-568 — and they are the ones a good foreman catches on site, which means they are also the ones that cost a day when he catches them at the wrong moment.

Electrical into RF. Variable-frequency-drive harmonics and conducted EMI, coupling into a wireless design that was drawn as if the electrical room were not there. IEEE C62.45 and ITU-R SM.1541 cover the mechanisms. Nobody discovers this in a coordination meeting; they discover it when coverage in that zone is bad and the argument about whose fault it is starts.

Electrical into audio. Ground loops and 60 Hz hum from power-cable proximity — the same IEEE C62.45 physics, a different symptom. The speaker hums, the microphone gets blamed, and the cause is two trades’ worth of decisions made independently.

Why these are position-specific, not zone rules

The reason a checklist does not solve it: the same two systems are fine in one part of the building and a problem in another. It depends on the actual device positions, the actual closet locations, and the route the cable actually takes — not on a zone average.

That is the part worth computing. If the camera, the access point, the speaker, the panel and the cable routes are all placed against the same building model, then the interactions between them can be evaluated against real geometry, and a conflict carries a severity that changes the recommended fixes rather than sitting in someone’s head.

What you do not get yet, and it is the thing you would want

There is no enumerated conflict report to hand to a subcontractor. Detected conflicts change the design’s objective score and generate remediation actions today. The list — which systems, which zone, what severity, and why — is a commitment rather than a shipped screen.

So this is honest about where it sits: it will change the design before it is built, and it will not yet produce the coordination document you would take into a Tuesday meeting. If that document is the thing you need, it is not here.

Where it does reach your paperwork

The closeout end is built. The as-built package exports as PDF, PNG and DXF — rack elevations, schedules, camera install-verification photo pairs — and there is an interactive standalone HTML as-built that is a single self-contained offline file, which is a more useful artefact to hand an owner than a folder of drawings nobody opens.

The phase view is partial and worth stating as such: the 4D timeline scrubs the install phase by phase, with entities rendered as installed, ghosted ahead of their phase, or hidden — but it requires the project to carry a phase plan. It will show you a sequence; it will not invent one.

The narrow claim

Low voltage is one line on your sub list and one of the last trades in the building. The conflicts it brings are real, they are computable from geometry you could have before rough-in, and today most of them are found by a person standing under an open ceiling.

Moving that discovery earlier is worth a drawing. Finding it late is worth two weeks.

See how the cross-domain model works, what a design-build handoff looks like, or book a demo on a floor plan you are coordinating now.