How BIM Coordination Reduces Clashes and Saves Money on Site

Construction rework is one of the most expensive and preventable problems in the industry. Studies consistently show that rework accounts for 5 to 12 percent of total project costs — and on a $50 million project, that translates to $2.5 to $6 million in waste. A significant portion of this rework originates from design conflicts that were not identified until steel was already erected or ductwork was already installed.

BIM coordination — the practice of combining discipline-specific digital models into a federated whole and systematically resolving conflicts before construction begins — is the most effective tool the industry has to eliminate this waste. When executed well, it shifts the discovery of problems from the field (where changes are expensive) to the design phase (where changes cost almost nothing). This article explains exactly how that process works, what kinds of clashes it catches, and what the evidence says about the financial return.

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What Is BIM Coordination?

Building Information Modeling (BIM) coordination is the structured process by which design models from multiple disciplines — architecture, structural engineering, and MEP (mechanical, electrical, and plumbing) — are combined into a single federated environment and analyzed for geometric and workflow conflicts.

The process follows a repeatable workflow:

1. Model authoring — Each discipline creates and maintains its own model in its authoring tool (Revit, ArchiCAD, Tekla Structures, etc.).
2. Model federation — Models are exported (typically as IFC or NWC files) and combined in a coordination platform to create a single composite view.
3. Clash detection — Automated tests are run to identify geometric conflicts between elements from different models.
4. Clash review and assignment — Results are reviewed, duplicates filtered out, and each clash is assigned to the responsible party for resolution.
5. Resolution — Designers update their models to resolve the conflicts, adjusting routing, sizing, or structural elements as needed.
6. Documentation — Resolved clashes are logged and the coordination history is maintained for the record.

The person who manages this cycle is the BIM coordinator (sometimes called the VDC coordinator or model manager). Their role is part technical — running clash tests, managing file exchange protocols — and part managerial, facilitating weekly coordination meetings and keeping resolution on schedule.

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Types of Clashes: Hard, Soft, and Workflow

Not all clashes are equal, and treating them as a single category leads to poorly prioritized coordination efforts. There are three distinct types:

Hard Clashes

A hard clash is a direct physical intersection — two solid objects occupying the same space in the model. These are the most obvious conflicts and the ones that would be immediately visible during construction.

Examples:

• A supply air duct running through a reinforced concrete beam
• A sprinkler main crossing directly through a steel wide-flange column
• Electrical conduit bundles routed through a shear wall without penetrations modeled

Hard clashes are non-negotiable: one or both elements must be relocated or redesigned.

Soft Clashes

A soft clash (also called a clearance clash) occurs when two elements do not physically intersect but violate a required buffer zone — typically for maintenance access, code-required clearances, or installation tolerances.

Examples:

• A fan coil unit installed with only 150 mm of clearance where the manufacturer requires 600 mm for filter removal
• Electrical switchgear with insufficient front-of-board working clearance per NEC 110.26
• A beam flange within the swing radius of a valve handle

Soft clashes are often more dangerous than hard clashes in practice because they survive visual inspection during coordination but create serious operational problems after handover.

Workflow (4D) Clashes

A workflow clash (or 4D clash) is not a geometric conflict but a scheduling conflict. When a construction sequence is linked to the model, 4D analysis can reveal situations where two trades need to occupy the same area at the same time, or where a later-phase element is modeled in a position that would require an earlier-phase element to be removed.

Examples:

• The structural steel erection sequence requiring crane access through an area where concrete formwork is scheduled to be in place
• Prefabricated MEP modules requiring installation before the deck is poured, but modeled as if they are installed after

Clash Type	Detection Method	Consequence if Missed
Hard clash	Geometric intersection test	Physical rework on site
Soft clash	Clearance buffer test	Maintenance/operational failure
Workflow clash	4D schedule-linked analysis	Sequencing delay, access conflicts

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The Clash Detection Process, Step by Step

1. Choosing Your Software

The industry uses several platforms for clash detection, each with different strengths:

• Autodesk Navisworks Manage — The most widely used tool. Supports NWC, IFC, and a broad range of native formats. Powerful clash test configuration with grouping and filtering. Standard on most large projects.
• Autodesk BIM 360 Coordinate (ACC) — Cloud-based, collaborative clash management. Teams can view and assign clashes without local software. Integrates with Revit via the desktop connector.
• Solibri Model Checker — Rules-based checking that goes beyond geometry. Can validate code compliance, naming conventions, and component completeness alongside clash detection. Preferred in some European markets and for IFC-based workflows.
• Revit Interference Check — Built into Revit. Useful for quick intra-model checks but not suitable for multi-discipline federation across different authoring tools.

2. Setting Up Clash Tests

A clash test in Navisworks (and equivalent tools) defines which sets of elements to test against each other. The key decisions:

• Selection sets — Define which categories of elements belong to each discipline (e.g., “HVAC ducts,” “structural steel,” “sprinkler piping”).
• Clash type — Hard, clearance (soft), or duplicates.
• Tolerance — For hard clashes, a small tolerance (1-5 mm) filters out near-misses caused by modeling imprecision. For soft clashes, the buffer is set to the required clearance distance.

A well-structured clash matrix specifies every combination of disciplines to test. Testing everything against everything generates noise; testing only the pairs that are likely to conflict keeps the results manageable.

Test Name	Selection A	Selection B	Type	Tolerance
HVAC vs Structure	HVAC ducts + fittings	Structural steel + concrete	Hard	2 mm
Plumbing vs Structure	All piping	Structural elements	Hard	2 mm
Electrical vs HVAC	Conduit + cable tray	HVAC ducts	Hard	2 mm
MEP vs Architecture	All MEP	Walls + floors + ceilings	Hard	2 mm
Equipment clearance	Mechanical equipment	All elements	Clearance	Per equipment schedule

3. Grouping, Filtering, and Prioritizing Results

A large MEP-heavy project can produce thousands of raw clash results. Many of these are duplicates, already-known accepted conditions, or low-priority items. Effective filtering typically includes:

• Grouping by grid location or zone to cluster related clashes
• Filtering out clashes between items in the same system (e.g., a duct touching its own hanger)
• Applying status filters to separate new clashes from those already in review or resolved
• Prioritizing by type: hard clashes in critical path locations first

4. Assigning Responsibility and Tracking Resolution

Each clash is assigned to the discipline responsible for proposing a resolution. The standard approach is: the discipline that has more flexibility (typically MEP) routes around the discipline that has less flexibility (typically structure). Assignments are tracked in the coordination platform with a status field:

• New — Identified, not yet reviewed
• Active — Under review, resolution in progress
• Resolved — Model updated, awaiting re-test confirmation
• Approved — Confirmed closed after re-test passes
• Won’t fix — Accepted condition, documented with justification

Weekly coordination meetings cycle through the active list, with the BIM coordinator facilitating and tracking commitments.

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Real-World Cost Savings: What the Evidence Shows

The financial case for BIM coordination is well established.

The Stanford Center for Integrated Facility Engineering (CIFE) studied 32 major projects and found that BIM adoption — of which coordination is a central component — generated:

• Up to 10% reduction in contract price
• Up to 7% reduction in project duration
• Cost estimation accuracy within 3% compared to industry averages of 10-15%

A McGraw-Hill Construction SmartMarket Report found that 74% of BIM users reported positive ROI, with the highest returns coming from reduced clashes and improved coordination.

A Concrete Example

Consider a $50 million mixed-use commercial and residential tower. A project of this scale typically involves:

• 40+ floors
• Complex MEP systems (variable air volume HVAC, high-pressure domestic water risers, medium-voltage electrical distribution, fire suppression)
• Multiple subcontractors with separate modeling responsibilities

Without structured BIM coordination, industry data suggests this project would encounter 200-400 site-discovered clashes requiring field resolution. Each field clash costs an average of $1,500 to $5,000 to resolve (material changes, additional labor, downtime, supervision time). At the midpoint:

• 300 clashes x $3,000 per clash = $900,000 in rework costs

With a structured coordination program, projects of this type typically reduce field clashes by 70-90%. Even at 70% reduction, that is $630,000 saved — on a coordination program that costs roughly $150,000-$250,000 in BIM management labor. The net return is $380,000 to $480,000, achieved before a single shovel hits the ground.

On larger projects, the numbers scale accordingly. Infrastructure and hospital projects routinely cite savings of $5 to $15 million attributed directly to pre-construction coordination.

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BIM Coordination Workflow in Practice

The Weekly Coordination Cycle

Effective BIM coordination runs on a structured weekly rhythm:

1. Model submission deadline (e.g., Monday noon) — All disciplines export updated models.
2. Federation and clash run (Monday afternoon) — BIM coordinator combines models and runs the clash matrix.
3. Clash report distribution (Monday end of day) — Results distributed to discipline leads with new clashes highlighted.
4. Coordination meeting (Wednesday, 1-2 hours) — All leads review active clashes, agree on resolution approaches, set deadlines.
5. Resolution work (Wednesday-Friday) — Designers update models to implement agreed solutions.
6. Repeat — Updated models submitted the following Monday.

Level of Development Requirements

Clash detection is only as good as the models used. Level of Development (LOD) defines how completely elements are modeled. For coordination purposes:

• LOD 300 (minimum) — Elements are modeled with sufficient accuracy for interference checking. Sizes, shapes, and locations are as-designed.
• LOD 350 — Interfaces between systems are modeled, including support hangers, sleeves, and connections. Required for meaningful MEP coordination.
• LOD 400 — Fabrication-level detail. Used for prefabrication and installation coordination.

A common coordination failure is running clash detection against LOD 200 models — conceptual massing without real system sizes. The results appear clean, but the models do not represent reality. The BIM Execution Plan (BEP) must explicitly require the LOD at which coordination will be performed and enforce submission deadlines tied to that standard.

The BIM Execution Plan

The BIM Execution Plan (BEP) is the governing document for a project’s BIM workflow. For coordination, the BEP should define:

• Authoring software and version requirements for each discipline
• Model file naming conventions and folder structure
• Coordinate system and shared project base point
• LOD requirements at each project milestone
• Model exchange frequency and format (IFC, NWC, RVT)
• Clash detection responsibility (who runs tests, who manages the platform)
• Resolution workflow and status definitions
• Accepted clash conditions and sign-off procedure

Without a BEP, coordination tends to be ad hoc, inconsistent, and underdocumented — which means the coordination history cannot be relied upon for dispute resolution if problems arise on site.

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Common Coordination Challenges and How to Address Them

Model Ownership Disputes

When a clash occurs at the boundary between two disciplines, each party may claim the other is responsible for resolving it. A clear clash resolution matrix — established at project kick-off — defines which discipline moves for each type of conflict. The general hierarchy: architecture is fixed, structure is fixed, gravity systems have priority over pressure systems, MEP routes around structure.

LOD Mismatches Between Disciplines

The structural engineer delivers at LOD 350 while the MEP engineers are still at LOD 200. Clash detection between these models produces false negatives — the MEP looks clear because ducts are undersized in the model. The fix is to enforce LOD milestones in the contract and verify compliance before running coordination tests.

Late Model Submissions

A subcontractor submits their model two days late every week, stalling the entire coordination cycle. The BIM coordinator should escalate to the project manager and, if necessary, the owner. Late submissions must be a contractual issue, not just a BIM issue — the BEP should specify consequences for missed deadlines.

Software Interoperability

A structural engineer using Tekla Structures, a mechanical contractor using CADmep, and an architect using Revit all need to exchange models. IFC (Industry Foundation Classes) is the open standard for this exchange, but IFC exports from different software vary in quality. The BEP should specify IFC version (IFC2x3 or IFC4) and require discipline leads to validate their IFC exports before submission.

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Best Practices for Effective Coordination

Federated model management — Never merge models into a single file permanently. Maintain each discipline model independently and re-federate for each coordination cycle. This preserves model ownership and simplifies troubleshooting.

Clash matrix documentation — Publish and version-control the clash matrix. When project scope changes (a new plant room is added, a floor is added), the matrix must be updated to include new element categories.

Priority classification — Not all clashes require immediate resolution. A three-tier classification focuses effort:

Priority	Description	Resolution Deadline
Critical	Blocks construction progress; structural or life-safety impact	48 hours
Major	Will require field rework if unresolved; significant cost impact	1 week
Minor	Small clearance issues, low-cost resolution	Next coordination cycle

Resolution tracking dashboards — Maintain a running dashboard that shows total clashes identified, open vs. closed by discipline, and trend over time. A healthy coordination program shows a declining clash count week over week as design matures. A flat or rising count signals that models are not being updated or that new scope is being introduced faster than it is being coordinated.

Accepted clash register — Not every clash must be resolved by model change. Some conditions are physical but intentional (a pipe penetrating a wall with a sleeve, for example). These are reviewed, approved by the relevant parties, and logged in an accepted clash register. This prevents them from re-appearing as “new” clashes in future runs.

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Conclusion

BIM coordination is not a single software tool or a one-time review — it is a structured, repeating process that must be embedded into the project’s contractual and workflow framework from the outset. When it is done well, the return is measurable: fewer field clashes, lower rework costs, shorter schedules, and a construction process where the problems have already been solved on screen before they can become expensive on site.

The investment in coordination — in software, in trained BIM coordinators, in weekly meeting time — consistently returns multiples of its cost. For project owners and contractors who are still treating coordination as optional or as a contractor responsibility without contractual teeth, the industry evidence from the past two decades is unambiguous: the projects that coordinate rigorously are the projects that finish on budget.

For AEC professionals looking to build or deepen their BIM coordination skills — running clash tests, managing federated models, facilitating coordination meetings — formal training accelerates the learning curve significantly.

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