Home Building: Breaking Down BIM

The core of BIM centers around the creation of 3D models of a home. All of the elements of the home—from the roof trusses and the drywall to the kitchen island and the bathroom tile—are represented as solid objects in the 3D environment. This is what distinguishes BIM from simple 3D drawings: Rather than just being lines on a screen, each object carries the same properties it would in real life. The size, shape, and material composition of each object is noted, creating a complete, living picture of the home exactly as it will be built.

BIM doesn’t stop with the completion of the model though, says Joe Sirilla, design department head at Monta Consulting & Design (MCD), an Altamonte Springs, Fla.-based design and engineering firm. In fact, creating the model is just the first step. And that, Sirilla says, is the key to understanding BIM and all of its potential for home builders—to stop thinking of it as technology and to start thinking of it as a process.

“It’s a process where all the individuals involved, using their software together, can interact and create one project in a 3D virtual world,” he says.

It is generally accepted among designers using BIM that there are eight stages to the process. Each step adds greater complexity to the 3D model, looking at factors such as sustainability, life cycle of the building, and material costs.

While the technology is an integral part of the process, builders have to be careful not to get caught up in the trappings of a pretty model. Some less-than-scrupulous companies engage in a practice Sirilla calls BIM-washing, where they’ll produce a 3D model without engaging in the ongoing, collaborative process that occurs afterward. “They’ll say, ‘Yeah, we’re using BIM,’ when they really mean, ‘Yeah, we’re using 3D,’ and they’re not doing anything more,” he says.

Levels of BIM

BIM is a process whereby a builder creates a home in a 3D environment to better define construction ahead of the actual build. Steps in the BIM process, as described by Sirilla, include:

2D: Is all about plans and specifications. “We’ve done it since people were using drafting boards before computers. But even with that, there can be disconnects and missed steps.”

3D: “Involves visualization and coordination of the project before it begins, and identifying design conflicts before field work starts.”

4D: “Is the model-based phasing of the construction process. It helps builders gain control over their trades’ material installation.”

5D: “Includes model-based cost definition, with accurate costing based on precise measurement information. It aims at zero waste by utilizing whole pieces rather than parts of materials, resulting in fewer dumpsters going to landfills.”

6D: Assesses the types of materials to be used, the life cycles of those materials, and how long those materials could last in specific climate conditions.”

7D: Looks at the life cycle of the building, including its operation and maintenance.

8D: Is the integrated product development and project delivery using all of the processes above, producing a well-rounded and thoroughly calculated project.

Without following the entire process, says Sirilla, builders won’t be able to reap the significant savings possible from using BIM. “If you have the right team performing the BIM process on your model or your design that team could help save anywhere from 10-to-30 percent on a home when it’s ready to be delivered,” he says.

Such substantial savings are wrought from the 3D objects that make up a BIM model. Since each object sports the same characteristics as it would in real life, builders can determine precisely how much of a given material they’ll need before construction even begins. Sirilla calls this a cost-based definition. “We’re taking the guesswork out of it, we’re taking overages out of the equation, and we’re keeping it an exact quantity,” he says.

Builders who use BIM say putting the pieces together virtually first lets you find any possible construction issues before you start building, like overlapping plumbing and structural components. “Having one master model for a particular plan lets you quickly see what works and what doesn’t,” says Brad McCall, co-owner of Billings, Mont.-based McCall Homes. “It’s much easier to catch a problem when it’s in 3D.”

If the technology and processes behind BIM can have such a huge upside for builders, why are many still reluctant to start using it? There are a number of reasons, says McCall, the most basic one being a lack of understanding and comfort with the status quo. “I think most builders are so entrenched in the processes they have that they’re reluctant to try something new,” he says.

There’s also the issue of incompatibility among the different BIM software. Each program has its own type of output, which often conflicts with other programs. That’s why groups like the American Institute of Building Design (AIBD)—for which Sirilla is the National BIM representative—are working to establish a national standard for BIM users and software. “We’re creating a level platform where all of the software companies would basically use a specific output so all the trades involved in the design process can collaborate and work together properly,” Sirilla says.

Before McCall Homes started using BIM, Brad did two years of research and preparation before he began implementation. He connected with CG Visions, an Indiana-based BIM consulting firm, and they sent a team out to Billings to evaluate McCall Homes’ processes and determine exactly what the company wanted BIM for. From there, they were able to help the builder find a suitable solution and implement it. “Working with the consultants up front helped us avoid a ton of potential early pitfalls,” McCall says.

MCD offers a similar service, which it calls the MCD BIM for Builders Program. “We sit down with the builder’s team and say, ‘What do you want to see out of a better operation?’ or ‘What do you feel is missing from your operations?’” Sirilla says. “And we’ll say this is how BIM can apply to this type of situation.”

For builders thinking of making the switch to BIM, McCall and Sirilla both say that it starts with taking a long, hard look at your own operations and your intentions. “If you’re going to make the investment, the process and why you’re doing what you’re doing are the most important things to consider,” McCall says.

Choosing BIM software—or a design firm—can be overwhelming as well, with each suite having its own set of advantages. Sirilla says the most important thing to keep in mind is which level of cost savings you hope to achieve. “The best scenario is one firm handling the design from A to Z, and that firm also handling the building design, engineering, truss engineering, mechanical, and so on,” he says. “That’s where a team like ours really is able to give those cost savings to the builder because we roll all of it into one package.”