Most construction companies have their own execution plans and guidelines for creating construction schedules. These schedules usually have to be broken down based on locations, building systems, or work packages. This article will walk you through the best practices of breaking down your master schedule to make it easier to create 4D BIM.
The most important aspect of creating 4D BIM is to breakdown both BIM and Schedule in the same manner. For example, if you know that your BIM models are coming from subcontractors in the form of one BIM model for every building system (e.g. electrical, HVAC, firefighting, plumbing, etc.), then you should breakdown your schedule using the same building systems. This way it will be much easier to identify which elements should be attached to which schedule activities. If BIM models are being created in house, then all you need to do is coordinate with the BIM department (or whoever is creating these BIM models for you) to match the breakdown of the schedule. Follow the instructions below while creating your schedule to make it easier to create 4D BIM.
Find Out the Breakdown of BIM Models
The first step is to identify the breakdown of your BIM models. BIM models can be broken down in any of the following ways:
- Based on Location
- In this approach, there will be one BIM model for each location in the building (e.g. each floor).
- Based on building systems
- In this approach, there will be a BIM model for each building system (e.g. structure, plumbing, HVAC, etc.)
- This approach works well with the UniFormat classification of construction activities.
Once you identify the breakdown approach of BIM models in your project, you can use the same method to breakdown your schedule.
What if the models are not available?
In this case, use UniFormat to breakdown your schedule activities. UniFormat is based on building systems, and it is the default way to breakdown models in most BIM modeling tools (e.g. Autodesk Revit).
Create Unique Activity IDs
When creating your master schedule activities, create a unique ID for each activity that reflects the following information:
- Activity Level
- Building System (UniFormat)
- Location (e.g. floor)
- Building Material (Master Format)
- Subcontractor (if possible)
This will help you significantly in many applications including cost estimating and 4D BIM creation.
Schedule Level of Detail
Schedule level of detail should match BIM level of detail. For example, if you have a concrete slab that will have 3 pour breaks, you should first check the BIM and make sure that it has those pour breaks. If the BIM has only one object for the whole slab, then you can do one of the following options:
- Recommended Option: Update BIM to reflect 4 objects for the slab, and link one object to each schedule activity
- This is the most detailed and recommended method of visualizing construction
- Change the schedule to include only one activity for the whole slab.
- This will reduce the granularity of the 4D BIM
- Keep the schedule and BIM as-is and link all four activities to the same slab object.
- The construction sequence visualization will be less accurate in this case.