During the pre-construction phase, the use of BIM models improves collaboration among architects, engineers and contractors. In addition, BIM models can also lead to better cost estimates. Here our panel of experts examines how BIM models affect pre-construction. Once again, our experts are:
- Erika Epstein, owner, Erika Epstein Architect
- Duane Gleason, project manager, Vico Software
- Michael Smith, BIM/Revit and MEP consultant, BIMWORKSINC
- Thor Wiggins, BIM/CAD manager, KSi Structural Engineers
Epstein: With architects and consultants (mechanical, electrical, landscaping, etc.) all using BIM models, we can more easily collaborate during the design process to minimize errors and to be more efficient and productive. As the design progresses, and decisions are made about systems and materials, we continue to update our shared BIM models; we also start to embed data, such as material choices, into the models. We also use clash analysis software such as Solibri and Autodesk Navisworks to identify every clash, not just the ones you happen upon as you review the overlaid models. Everyone works smarter, and the team result is far better coordinated with fewer errors. If the contractor is brought on board before the traditional bid period, he can also make use of the information embedded in the BIM models. Ideally, contractors can add information to the models that allow them to pull out costing and material quantities. IFC, a non-proprietary file format, allows the exchange of models and their data from one program to another. This type of file lets everyone work in the program of his choice and still share work with the rest of the team.
Gleason: It really depends on how savvy the contractor is, and how committed he is to BIM. It is undeniable that some of the contractors out there still just have the software, and they talk about it, and they see the beauty of it, but they are not really fully using it. For them, the process is different for the first couple weeks, but then it kind of gets back to the same old routine. However, for the contractors who have really embraced BIM, it changes the entire dynamic once the project is handed over to them. They are pushing coordination from day one, and they are holding their efforts to the data that is inside the models from day one, and linking submittals to the models, and tracking as much as they can through the models.
I don't think there are a lot of architects yet handing over the models, so it is going to need a couple more years of refinement before things begin to change quickly. But what we are seeing now is that general contractors who are getting the jobs see the value of the BIM models. By having a 3D model for pre-bid, they are able to flesh out any missing information, see any conflicts and optimize the project. BIM shifts the focus to planning so that, once the building starts, there are few surprises.
Smith: With BIM models in hand, the contractor can bid the project with a higher degree of confidence that his estimate is more representative of the reality of construction and that there is less chance of hidden costs or hidden problems that can really impact the bottom line. There are also the benefits BIM provides in terms of quantity takeoffs and other information that the contractor really couldn't get from traditional 2D drawings.
BIM models are great databases for quantity takeoffs. If certain criteria can be established early in the design process, such as make, model and costs, then the objects that are placed in the model can have critical parameters assigned. So, now, quantities of items and their costs can be estimated very quickly. There is something to be said also for the opportunities that exist for those contractors who are getting BIM savvy. In today’s hard economic times there is an opportunity with regards to stimulus dollars and government work, but it may take some special preparations to actually get in on that kind of project. This is where certain BIM consultants can help people understand the requirements of doing a government job.
Wiggins: The use of BIM models saves the contractor quite a bit of time and coordination. They can receive a model, or several models, from the design team and get instant material takeoffs. We designed a project in which the contractor was Holder Construction. The project was a 14-story office complex, cast in place concrete on top of a six-level deck on auger cast piles and pile caps. When I released my model to Holder, they performed an initial material take off from the model. Then they had their senior estimator spend four or five days doing a second material take off from the structural contract documents. There was a one percent difference between the two estimates. As a result of having BIM models, within a matter of two hours they can have the information they need to price a job competitively.
The next section of our introduction to Building Information Modeling looks at how a BIM project is different for subcontractors who are used to the more traditional method of building construction.