The Ultimate Clash Detection Guide
Clash Detection is the process of using 3D models to identify clashing elements between disciplines. This improves the coordination of construction projects by reducing errors in preconstruction.
Table of Contents
What Is Clash Detection
Clash detection is the automated process of identifying where building elements (like pipes and beams) physically overlap in a 3D BIM model before construction begins.
Clash detection identifies both Hard Clashes (physical intersections) and Soft Clashes (clearance or maintenance issues).
The goal of clash detection is to prevent as many on-site issues from arising during construction as possible by resolving identified clashes during preconstruction.
Clash Detection In 60 Seconds
When To Use Clash Detection
Clash detection is beneficial on projects of almost any size.
It shines on projects with tight ceiling spaces, complex mechanical design, and areas with several systems intersecting.
What You Get From Clash Detection
A prioritized clash report with clear locations and screenshots, plus coordination-ready markups and a description so trades can make decisions and update their models.
Typical Clash Detection Workflow
We collect (or build) the required discipline models, federate them into one coordinated model, run clash detection, then triage and prioritize the issues into a clear report you can send to the design and consulting team.
Common Clash Detection Pitfalls
There are a few common pitfalls to running clash detection:
Outdated or misaligned models
Clash fatigue” from too many low-value issues
Unclear responsibility for fixes
Why Invest In Clash Detection?
💰 Massive Return
Make more profit on your projects and reduce costs by using clash detection.
On every project we have a chance to work on, clash detection consistently has a massive return on its cost.
- Problems are far cheaper to fix in precon
- Free up your site team to focus on site problems
- Keep your project on schedule
On the Steveston Washrooms, clash detection was responsible for $141,000 in savings on a $3 million project.
👷 Install With Confidence
Clash detection reduces risk on your project and helps with schedule certainty.
No more tying up your site teams with preventable coordination issues, instead, they are free to address everything happening on site.
- Reduce RFI delays
- Less rework on site
- Fewer schedule delays
On the Steveston Washroom Project we identified 16 major issues that helped streamline the site – on a project just $3 million in size.
How Does Clash Detection Work?
There is no magic button clash button. Clash detection is done by using a structured workflow of combining models, setting rules, and filtering noise.
The "Federation" of Models
We take the separate design models (Architectural, Structural, Mechanical, Electrical etc.) and combine them into a single Federated or Integrated Model.
Setting Rules & Tolerances
We tell the software what to look for using specific Search Sets. We don't just "check everything against everything."
- Hard Tolerance: Flag if a pipe hits a beam by >10mm.
- Soft Tolerance: Flag if a pipe wall is within the required free area of a roof top unit. (Clearance).
The "Human" Triage (Crucial)
Software can find thousands of "clashes" but often many of those are noise. This is where Pixel BIM and all our experience adds tremendous value. We review every clash to separate True Issues from False Positives so you can focus on fixing what's important.
Report & Resolution
Validated clashes are grouped into Clash Groups and put together into an actionable report. See our deliverables section below for an example of exactly what a clash report looks like.
The Coordination Timeline
When Should You Start?
The most common question we get is "Is it too early?" The answer is almost always no.
You can start as early as the Building Permit (BP) stage. Catching a major shaft misalignment here costs $0. Catching it during shop drawings costs weeks of schedule.
Building Permit Drawings (BP Drawings)
Before a shovel hits the ground, we run clash detection on the consultant models, or produce the models to run clash detection if you don't have them.
This stage helps will find less clashes comapred with IFT, or IFC drawnig sets, but helps to start your project off from a coordinated base that sets your whole project up for success from the start with less redesign down the road.
IFT and IFC Coordination
These are the most critical drawing stages for clash detection. We update the models from the generic design models to highly-detailed models.
The goal here goes beyond design intent, and instead to help create certainty for your trade partners and site teams.
This is the stage where general contractors typically get us involved on their projects.
Construction Phase
Typically, consultants are no longer responsible for updating models or the base drawings after the IFC set is issued.
You may choose to keep running clash detection while updating the models with shop drawings, site instructions, and change order documents to keep your project coordinated right through substantial completion.
As an additional benefit, the model can then be used to produce as-built drawings or hand over an as-built model to the client for use in maintenance and future renovations.
What Does Clash Detection Find
Clash detection highlights the conflicts and clearances that can turn into RFIs and rework later.
Hard Clash
Physical elements intersecting between two elements in the building.
Example: Duct shown intersecting with a steel beam.
Soft Clash
Clearance or maintenance related clashes typically due to insufficient space.
Example: Insufficient clearance around a roof top mechanical unit.
Scheduling Clash
Typically called 4D scheduling, (or workflow clash). Identifying out of sequencing work.
Example: Mechanical unit delivered before pad poured.
Steveston Park Facility
"On a $2.7M project, we identified 42 critical issues before construction. The BIM process alone saved 8.36% of the total project cost."
The Challenge
Public infrastructure projects like the Steveston Park Washrooms operate on fixed budgets with zero room for overruns. With a project value of $2.7M, any site conflict or change order would directly impact the bottom line.
The Solution
We ran a full coordination report, identifying 16 major hard clashes and 13 coordination issues. By calculating the cost of fixing these on-site versus in the model, the value became undeniable.
We saved the Site Superintendent an estimated 75 hours of troubleshooting time, allowing them to focus on logistics and safety rather than solving design conflicts in the field.
Get These Results For Your Project →What We Flag Vs What We Ignore
Flagged Clashes
- Shafts & risers (tight vertical routes)
- Corridors and dense ceiling spaces
- Mechanical and electrical rooms
- Major mains (duct trunks, hydronic mains, sprinkler mains)
- Code, access, and maintenance clearances
Ignored Clashes
- Minor fasteners and small fittings
- Tiny overlaps that don’t affect installation
- Duplicated “repeat” clashes from modelling artifacts
- Non-constructability noise that trades won’t act on
Clash Detection Deliverables
We don’t send you 500 hundred clashes in an excel file. We give you actionable reports to make issues easy to resolve.
More Than Just A Screenshot
We pride ourselves on giving you the clearest and most actionable report we can produce. Every clash we find comes with:
- Location data Level, gridlines, and sheet name
- 3 screenshots The clash in 3D and the 2D plan location of each drawing discipline
- Clear description Concise explanation of what we found
The Clash Detection Matrix
We leave nothing to chance and cross check every possible model combination to identify as many clashes as possible during preconstruction.
If you have, or would like to include, we will add fire protection, civil, and landscaping.
Visualizing our clash detection process.
What Is The Best Clash Detection Software?
We primarily use Revizto for clash detection and have found it to be the best clash detection tool on the market. Here is why:
| Category | Revizto | Autodesk Navisworks |
|---|---|---|
| Best for | Coordination & Communication Clear issue tracking and keeping all stakeholders aligned. |
Deep Analysis & Rule Sets Deep model aggregation and robust clash rule sets. |
| Pros |
|
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| Cons |
|
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| Clash Strength | Strong for coordination-focused workflows with practical triage. | Best-in-class for detailed rule creation and high-volume management. |
| Issue Tracking | Built-in: Assign, comment, attach screenshots, set due dates. | External: Typically requires spreadsheets, ACC, or 3rd party tools. |
| Collaboration | Designed for coordination meetings and trade-friendly review. | Effective for VDC-led review, but often requires extra tooling. |
| Reporting | Clear logs and shareable outputs for fast distribution. | Requires significant grouping/triage to prevent "noise." |
| Ease of Adoption | High (Easy for PMs/Trades) | Medium/Low (Steep learning curve) |
| Common Pitfalls | Letting issues pile up without owners/due dates. | Producing huge clash lists without a clear triage process. |
Do You Need an In-House BIM Manager?
For many general contractorss, the math of hiring full-time doesn't add up. Compare the true cost of building vs. partnering.
The Internal Hire
High Fixed Cost- Salary & Benefits: High fixed overhead regardless of project volume or downtime.
- Software Costs: $10,000 per year (AEC Collection, Revizto, Bluebeam, Office, etc).
- Hardware: $4,000+ per high-performance workstation.
- Ramp-Up Time: 3-6 months to train and integrate into workflows.
- Additional hires: As you introduce BIM and clash detection on more projects, you will need to hire and train additional staff to handle the workload.
Partnering with Pixel BIM
Recommended- Pay Only For What You Need: Zero "idle time" costs. You only pay when you have an active project.
- Scale Without Hiring: Expand your BIM capacity instantly without adding headcount or HR headaches.
- All-Inclusive Tech: We bring our own licenses (Revizto, Navisworks) and hardware.
- Senior Talent: Led by Chelsea with more than a decade of BIM experience with general contractors.
Frequently Asked Questions
Common questions about the clash detection process and deliverables.
No. While modern software uses advanced algorithms, standard clash detection is a geometric process, not Artificial Intelligence. It uses 3D BIM models to identify physical overlaps based on specific rules and tolerances set by a VDC Manager. The "intelligence" comes from the human expertise used to filter false positives.
It depends on the project delivery method. While architects manage "design coordination," the General Contractor is typically responsible for construction-level clash detection. GCs often hire a third-party specialist like Pixel BIM to manage this process impartially between trades.
They perform "Visual Coordination," but rarely full Clash Detection. An architect's focus is design intent, whereas a BIM or VDC Manager’s focus is constructability and installation. This is why a dedicated clash detection round is vital before construction begins.
The primary benefit is cost avoidance. Resolving conflicts in the 3D model is significantly cheaper than fixing them on-site. Key benefits include drastically reduced RFI delays, zero rework during installation, and greater schedule certainty.
Costs vary based on project square footage and complexity (e.g., a hospital costs more to coordinate than a warehouse). However, the industry standard ROI is significant with us finding a 600% ROI on the Steveston Washrooms Project.
The industry standards are Autodesk Navisworks and Revizto. We utilize both to ensure compatibility with all major design tools like Revit, CAD, and IFC files.