Imagine being in a BIM coordination meeting and listening to the project’s BIM coordinator describe a hard clash at the mechanical area, a soft clash on the second-floor level, and an entire federated model that must be reviewed by Friday. You are nodding your head as you try to understand half of what the people in the room are saying.
This is a situation which frequently comes up at work. Knowledge of clash coordination jargon is not only about giving yourself an air of authority during the meetings, but it will allow you to better communicate with the designers and avoid any issues which may prove to be expensive later. In this course you will learn:
- The basics: clash detection, BIM coordination, and 3D clash coordination.
- Types of clashes & clash documentation: hard versus soft clashes, workflow clashes, federated models, clash reporting, and clash matrix.
- People & process: BIM Coordinator, constructability review, and LOD (Level of Development).
What Is Clash Detection?
Clash Detection refers to the procedure of determining whether various building components collide or come into conflict with one another within a 3D model. Rather than finding out after the team has been brought on-site that there is an overlap between the beam and the duct, this happens well in advance on-screen.
Using software such as that of Navisworks to detect clashes makes sure that all clashes found within the model are detected by running through it automatically.
Understanding BIM Coordination
BIM coordination is the general term under which clash detection falls. It is the continuous collaboration between architects, engineers, and MEP coordinators to reconcile the designs of all disciplines into one coherent design plan before construction begins. BIM coordination can be likened to the referee who ensures that ductwork, pipe work, and structure do not fight for the same ceiling space.
3D Clash Coordination Explained
3D clash coordination is an advanced form of clash detection where the conflicts are sorted out collectively in the 3D space and not only highlighted. Teams sit down, review the model and make a decision on what to do about it in order to resolve the conflict in real life.
Hard Clash vs. Soft Clash
These two terms come up in almost every coordination meeting, and they mean very different things:
- Hard clash: Two solid elements physically occupy the same space, like a sprinkler pipe running straight through a steel beam. These must be fixed before construction, since two solid objects can’t share the same spot.
- Soft clash: Also called a clearance clash. Nothing technically overlaps, but a required clearance zone is violated, such as a duct installed too close to an access panel a technician needs to open later. Soft clashes still matter because they affect maintenance and safety.
What Is a Workflow Clash?
A workflow clash isn’t about geometry at all. It happens when the construction sequence itself creates a problem, like an electrical rough-in scheduled before the wall framing it depends on is even built. Catching workflow clashes early keeps trades from showing up to a site that isn’t ready for them.
Federated Model and Coordination Model
- Federated model: Created by combining individual discipline models, architectural, structural, and MEP, into a single linked view without merging them into one file. Each team keeps ownership of its own model, but everyone sees how the pieces fit together.
- Coordination model: The working file used specifically during coordination meetings to run clash checks, mark up issues, and track resolutions as the design matures.
Clash Report and Clash Matrix
- Clash report: A document that lists every detected clash, including its location, the disciplines involved, and its current status. It’s the record everyone refers back to so nothing slips through the cracks.
- Clash matrix: A grid that defines which disciplines get checked against each other and how strict the tolerance should be for each pairing, keeping the process organized instead of checking everything against everything.
BIM Issue Tracking
The clash management process in BIM is the method used by a team to track any issues that arise during the process until their resolution. This is different from using emails where accountability might be lost since all issues are recorded in one place.
Who Is a BIM Coordinator?
The BIM coordinator manages the entire coordination process. This position can mean the difference between effective coordination and chaos on large projects. Some typical duties are as follows:
- Scheduling the BIM coordination meeting so every discipline stays on schedule.
- Reviewing the federated model for clashes before the team meets.
- Assigning clashes to the correct discipline so the right team owns the fix.
Constructability Review
Constructability review involves more than just clash detection and examines whether the design can actually be constructed as shown. This includes things like accessibility for installation and maintenance, and construction sequence feasibility.
Level of Development (LOD)
Level of Development, or LOD, describes how detailed and reliable a model element is at a given project stage. Knowing the LOD of a model tells you how much you can actually trust it during coordination:
- LOD 100 – conceptual placeholder, rough massing only.
- LOD 200-300 – approximate geometry, general size and shape.
- LOD 400 – fabrication-ready detail.
- LOD 500 – verified as-built condition.
Why BIM Clash Coordination Makes a Difference
The table below lays out a simple comparison between projects that use proactive BIM clash coordination and those that don’t.
| Project Aspect | With BIM Clash Coordination | Without BIM Clash Coordination |
| Design Conflicts | Detected before construction | Found during construction |
| Rework | Minimal | Frequent |
| Project Cost | Better controlled | Higher due to changes |
| Construction Delays | Reduced | More common |
| Communication | Better collaboration | Miscommunication between teams |
| Material Waste | Lower | Higher |
| Construction Quality | Improved | Greater risk of errors |
| Project Delivery | More predictable | Increased schedule overruns |
It is always cheaper and quicker to spot an issue through the computer screen than on-site. Coordination ahead of time cannot completely eliminate surprises but helps in avoiding the costly ones, as well as giving every tradesman a better understanding of what awaits them.
A Real-World Example
These words can occur in combination like this in a project scenario. While constructing a hospital wing, the MEP coordination team conducts 3D clash coordination meeting where the hard clash of an HVAC duct with a structural beam is identified. In this case, since it has been discovered in the design stage only, the mechanical engineer redesigns the HVAC duct digitally within just a few hours, rather than after it gets hung and then cut down to size on-site.
Bringing It All Together
It is not necessary for you to be a dedicated BIM coordinator in order to participate in such a meeting. Knowing these definitions will give you enough background knowledge to pose the proper questions, challenge any decisions that seem impractical, and track changes made in the coordination model. Some key points to note:
- A hard clash fixes what’s physically colliding; a soft clash protects clearance and access.
- BIM coordination keeps disciplines aligned before a single trade shows up on site.
- A shared vocabulary translates directly into fewer conflicts, less rework, and more predictable delivery.
Whether you’re managing a small renovation or a large commercial build, that shared vocabulary is what lets you collaborate more effectively with architects, engineers, and BIM coordinators from design through delivery.
