Advancing 5D BIM

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It’s easy to hope for no construction-cost overruns, but much harder to achieve. Yet, that’s exactly what a growing number of construction and AEC companies are aiming to do. These firms are involving their estimators much earlier in the project planning process to inject a higher degree of cost analysis into critical decision-making discussions.

What makes this kind of collaboration possible? For many companies, model-based cost estimating (also known as 5D BIM) is helping their estimating team provide the value engineering feedback needed for greater cost predictability—and cost savings.

Overall interest in using BIM processes and tools to improve project delivery is rising among construction companies. In fact, 32 percent of contractors expect an increase in the amount of projects involving BIM this year, according to the 2016 Construction Hiring and Business Outlook conducted by AGC of America and Sage. Communication, collaboration and a contractor’s ability to impact the design process are some of the main reasons why contractors are increasing their use of building information models, says Dmitri Alferieff, AGC senior director of virtual construction.

Kevin Miller, professor at Brigham Young University, also sees growth specifically in the use of model-based cost estimating. "5-D BIM is being adopted on all fronts," he says, indicating that it’s not just firms with design and construction under one roof that are seeking the benefits of models. "Where you have a relationship between the contractor and the designer — more of a design-build approach — we see bigger strides being made than the traditional design-bid-build delivery method. But all fronts are advancing, just at different paces," he adds.

The relationship between the design and estimating teams as well as the quality of the 3D model are important factors in executing successful 5D BIM processes. And this is where there is still room for improvement. From an estimating standpoint, for example, no two 3D models are alike. "Designers differ in their knowledge of 3D modeling and the amount of estimating-related information they include in the model also varies," Miller says.

AEC firm STV, a member of AGC of Metropolitan Washington DC and AGC of New York State LLC, knows that difference all too well. "Where the quality of the design information permits, the quantities are dervived from the 3D geometry and embedded nomenclature of the objects in the model," explains Carl "Ozzie" Mest, senior cost estimator and systems administrator at STV. "Where a reduced level of design maturity is evident, the team resorts to 2D takeoff."

There lies the current challenge with 5D BIM. Building information models today typically don’t contain all the information required by estimators. For example, a 3D model may contain a pipe schematic with lengths, but estimators still need to refer to 2D drawings to take off the hangers.

Miller, who specializes in estimating from building models, acknowledges that many 3D modeling tools will generate 2D information from the model, including floor plans, specifications and notes. However, the workflow to extract that 2D information from the model isn’t an easy process. "It’s much quicker for estimators to use the 2D takeoff tools they’re used to," he says. Consequently, estimators currently have to use multiple, unconnected 2D and 3D takeoff systems, complicating the process and increasing the chances for error.

Even companies like STV, known for its innovative use of technology to improve the building process, would like to see a solution to this problem. STV has developed an interoperable platform that transfers intelligent data directly from the 3D model into the company’s estimating database through custom applications developed in-house. But even with this sophistication, they still have to deal with missing information from the model.

The reality is the majority of estimating takeoff is still done from 2D plans, and that isn’t expected to change anytime soon, if ever. "Estimators don’t yet trust the 3D models," says Miller, explaining that the models today are mostly used to double check a 2D takeoff.

Another concern with 3D models is the lack of specifications. From a design perspective — particularly for independent architects — there’s often little value to putting specs into the model. In fact, it may not be possible to build a model containing all the job specifications without impacting model size and performance. Designers could attempt to resolve this issue by creating links in the model to external specification documents. However, these links, which must be maintained by different team members, can easily break as specifications change throughout the project.

"The industry is still figuring out how to work with BIM to carry out projects more effectively," says Alferieff. "Greater communication is still needed so downstream users — such as estimators — better understand the usability and limitations of the models they are receiving."

But strides are being made. Alferieff points to the Level of Development (LOD) Specification, created by the BIMForum, which helps to specify and communicate the content and reliability of building information models at various stages in the design and construction process. The specification allows model authors to define models for specific information exchange, milestones in a design work plan, and deliverables for specific functions. Quantity takeoff is one of those functions.

Advances in estimating technology are also helping to tackle 5D BIM issues. "We are always looking at technologies to enhance and improve our BIM processes," says Mest. "Currently there are new takeoff products emerging that will accumulate information from the 3D model and allow the estimators to complete the 2D drawing takeoffs within the same suite of tools."

The ability for estimators to do production estimating work concurrently with 2D and 3D content will streamline the now fragmented takeoff process and improve accuracy. Also with the right technology tools in place, construction objects in a model can be directly linked to assemblies in a customized estimating database. These assemblies contain the necessary specification variables used by estimators.

"Technology is continuously advancing and the future will be driven by the quality of data that estimators are provided to work with as much as the tools available to process it," says Mest.

Today’s contractors are looking for better ways to collaboratively work with owners and other project team members to find the most cost-effective way to complete complex projects. 5D BIM processes, made more realistic with new technology, set the stage for reaching that goal.

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