Why clash detection is so important in modern construction projects
Modern construction projects are extremely complicated. A single skyscraper can have up to thousands of unique elements: structural columns and beams, HVAC ductwork, plumbing pipes, electrical conduits, fire protection system, architectural finishes – all of them occupying the limited space. Coordination between systems belonging to multiple disciplines is one of the biggest problems of modern construction projects.
And if the systems are not properly coordinated, there is a chance that a duct will penetrate a structural beam, that a pipe will occupy the same space as an electrical conduit, or that access zone for maintenance of some equipment will be obstructed by other equipment.
These types of problems when discovered at site are extremely costly and lead to rework and delays in construction.
That’s why clash detection in Building Information Modeling (BIM) becomes extremely necessary and important to solve these kinds of problems.
What is clash detection in BIM?
Clash detection in BIM is an automated procedure of checking if building elements from different disciplines have any kind of interference in the digital model. Clash detection software compares multiple discipline models – architecture, structure, MEP (Mechanical, Electrical and Plumbing) – in order to find coordination problems in them .
This process goes beyond just detecting errors in the model. Effective clash detection detects constructability problems that are significant at site, thus letting project teams prioritize the problems that occur at site over hypothetical ones. That’s how projects’ teams can virtually solve problems without spending additional money on rework.
Specialized clash detection software like Autodesk Navisworks, Solibri and BIMcollab Zoom detect inconsistencies when elements collide, overlap or have clearance violations. The results of clash detection are provided to users in form of a list of potential conflicts which are usually highlighted in the 3D model.
Types of clashes
However, not all kinds of clashes are the same. In order to prioritize the issues and choose an approach to resolve them project teams should understand what types of clashes they are dealing with. There are three main kinds of clashes:
1. Hard clash
Hard clash happens when two physical objects occupy the same space. It is the most basic kind of problem – for example, duct penetrating a structural beam or piping passing through a wall where it is not supposed to pass. Hard clashes are visual and obvious and can cause significant rework if they happen at site.
2. Soft clash
Soft clash happens when an element violates required clearances or tolerance zones even if it doesn’t physically touch any other object. For example, air conditioning unit may require access zone for maintenance that is occupied by a structural beam or a pipe that is running too close to electrical equipment violating safety clearances. Soft clashes are usually more subtle than hard clashes but still significant for construction and facility operations.
3. Workflow or logical clash
Workflow clashes (sometimes called 4D clashes) are related to sequencing or scheduling and installation requirements and do not involve any kinds of physical space conflict. For example, construction schedule may require drywall installation before ductwork installation behind it or equipment delivery after its installation. Workflow clashes are detected if BIM is integrated with construction schedule .
4. Clash detection workflow
In order to use clash detection effectively, teams have to follow certain steps. Here is the step-by-step guide for implementing clash detection.
Step 1: Prepare coordinated BIM models
At the first stage, teams gather BIM models files from all relevant disciplines in a common environment. They need to make sure that models are consistent: they have identical naming conventions, levels and coordinate system. If models don’t have a common coordinate system, the software won’t be able to detect if there are clashes or not.
Step 2: Upload models into coordination space
Modern clash detection becomes more and more cloud-based. Autodesk Model Coordination and Autodesk Construction Cloud are two popular platforms which aggregate all models in one shared environment. After models are uploaded to the platform, it can automatically detect clashes when new model version becomes available .
Step 3: Run clash detection tests
Clash detection software compares models pair by pair and detects conflicts between them. Teams can tune settings and tolerance to decrease noise and focus only on important issues. For example, teams can set a minimum clash threshold to filter out clashes with contact points smaller than a certain size.
Step 4: Review and classify clashes
Teams have to review clashes found by the software and group them by system and severity. It is important in order not to get overwhelmed with false positive clashes. Some clashes identified by the software are not actually issues – they may be intentional penetrations or acceptable close tolerances. Each clash is marked as an issue that needs to be resolved or irrelevant .
Step 5: Assign issues and track their resolution
Clashes marked as issues are converted to action items that are assigned to responsible parties. Issue management system tracks due dates, comments and status of issues in order to increase accountability and help with resolving issues. This is the connection between clash detection and project management.
Step 6: Re-check models after their updates
Because of constant changing of the models, clash detection has to be done repeatedly in order to make sure that issues are actually solved. Changing models can introduce new conflicts even if old ones are solved. Continuous coordination of models in design and construction stages is very important for having clash free model.
Why laser scan data improves clash detection
While design models are extremely useful for coordination, they represent intent – not reality. As-built conditions can differ from design assumptions because of installation tolerances, field adjustments and construction deviations.
Using laser scan or point cloud data to capture site conditions and validate design models can provide additional value . Laser scanning is especially helpful for renovation, retrofit and as-built verification projects because existing geometry can significantly differ from design assumptions.
For example, the team working on renovation of a building can perform laser scanning of the existing building and create a point cloud of it. This point cloud can be compared to BIM model in order to detect clashes between new design elements and as-built model. Pipes, beams and walls that were supposed to be located in a certain place in the design model may actually be located elsewhere creating conflicts that won’t be caught in design model .
Laser scanning can discover critical clashes that will otherwise go unnoticed. It is demonstrated in one mega-project example, where regular laser scans helped to discover 112 critical clashes in 12 months period .
Benefits of BIM clash detection
The financial and operational benefits of clash detection are proven. In the case study of a residential project in Mumbai it was found out that BIM-enabled clash detection helped to save $4,900 on a single major clash .
The main benefits of clash detection include:
- Reduction of field conflicts and rework – problems are resolved virtually and not on site where they are costly;
- Improving coordination between trades – common model reviewing gives common understanding between disciplines;
- Improvement of approvals and handoffs process – coordinated models require less clarifications during construction;
- Decreasing project risk – early identification of problems lowers uncertainty and delays;
- Improving constructability – designs are improved based on real ways of building;
- Improving communication – issue tracking provides more accountability and better document decisions.
Common challenges and best practices
Although there are plenty of advantages of clash detection, there are still some challenges associated with it. Poor quality of the model can generate too many false positives that will overwhelm teams with irrelevant data. Mismatching coordinate systems and incomplete modeling can lower accuracy of clashes detection and miss important issues.
Some best practices for successful clash detection include:
- Defining clear clash rules – establishing consistent clash rules, tolerances and priority levels before starting the coordination review ;
- Setting priorities – not all clashes are important. Project teams have to start resolving high impact conflicts first;
- Reviewing only the conflicts that matter – using filtering and grouping in order to eliminate irrelevant clashes;
- Using standardized templates – many coordination tools allow importing predefined clash test configurations .
Future of BIM clash detection
The future of clash detection is associated with more automation and integration of the process in regular BIM work flow. Using cloud coordination platforms allows monitoring clash detection constantly rather than using it as the final step. Data visualization and dashboard technology is increasing transparency of the progress in coordination and helping to monitor problem solving and increase accountability .
Distinguishing clash detection from issue management becomes more relevant for successful coordination. Clash detection identifies problems while issue management deals with tracking, assigning and solving them. Coordination becomes more efficient if you connect both processes .
With growing implementation of cloud collaboration, real-time model updates and automated coordination, clash detection will become even smoother process incorporated in regular BIM delivery.
Are you ready for more efficient project coordination?
At Camellia Buildtech we incorporate BIM clash detection and laser scan technologies in order to find conflicts before construction. Contact us to see how our BIM coordination services will help you to reduce rework and increase project visibility.
Frequently Asked Questions
1) What is clash detection in BIM?
Clash detection in BIM is an identification of conflicts in building elements within digital models prior to construction.
2) Why is BIM clash detection important?
It helps identify design conflicts, decrease rework, coordinate efforts and prevent problems on site.
3) What are the types of clashes in BIM?
The most common are hard clashes (intersections), soft clashes (clearance conflicts) and workflow or logical clashes (conflicts in scheduling).
4) How does clash detection software work?
It compares models of multiple disciplines within the same coordination space, finds conflicts automatically and allows team to review and assign issues.
5) How is laser scan data used in clash detection?
Laser scan provides data about the current state of construction site, which helps to compare reality with BIM model and detect problems not identified by design models.
6) Who needs clash detection?
Architects, MEP consultants, BIM manager, contractors and coordination team benefit from less conflicts and higher project visibility.
