Construction is full of risk and the need to make assumptions. It’s hard to be right all the time – especially during a renovation project when information on the existing building may be limited. Construction Managers must rely on previous experience and knowledge, as well as the right technology – like Building Information Modeling (BIM) – to manage that risk and overcome any potentially flawed assumptions. BIM is a sophisticated and dynamic tool that can uncover conflicts in a project’s design to flag constructability issues before they become too costly and time consuming to fix.

What is BIM?BIM is a layered, 3-dimensional, electronic model that represents exactly how the real building will be built in the field – with structual, plumbing, electrical, and HVAC components laid out in precise detail.

One of the major benefits of creating the building electronically first is clash detection. Each subcontractor creates a single electronic model for his particular layout. Then, the individual models are “federated,” or laid on top of each other, to create a consolidated model of the building. When that is done, the coordinator can run a clash detection to see if there are any problem areas. For example, if the plumbing subcontractor has laid out piping in the same space as the electrician’s wiring, the clash detection will catch that interference and allow for a fix to the plans before the clash becomes a problem in the field. The

ultimate goal of BIM is to create a model that’s so accurate and reliable, there are no field RFIs during the project because the model eliminated all of the issues beforehand.

BIM at Andover InnIn 2008, Erland’s design/build team (with architect, Arrowstreet) was hired to renovate the historic 31-room Andover Inn. After more than a year of intense preconstruction, work began in earnest during the fall of 2009. The inn, originally built in 1930, was in desperate need of a renovation, but Phillips Academy – the inn’s owner – was concerned that construction would destroy the historic value of the building. One of the major challenges for Erland was to complete the construction while maintaining the

historic look and feel of the hotel. In preconstruction, working with the school and architect, it was decided that the building should be completely gutted and rehabilitated—with the exception of the main lobby and dining areas, which were preserved because of the richness of their architectural detailing. Completed in late summer 2010, Andover Inn now features new mechanical and electrical systems, as well as a modernized look that blends contemporary style with the historical flavor of the inn.

Andover Inn remained in operation up until the day we started construction, severely limiting our access to the building to analyze the existing conditions. In addition, like many historic structures, there were no records or as-builts available for review. Our team

Managing Your Project Risk with BIM

By Chuck Vaciliou and John Cormier

had to make many design assumptions about the framework and layout of the structure – like what might exist behind the walls and how much space there was in the ceilings – in order to move forward with developing and finalizing the design. Unfortunately, once construction began, we discovered many unforeseen impediments.

At the start of the project, we had not intended to use BIM. But, as we began to open up walls and discover more about the conditions of the building, we realized that our initial design assumptions would not work. The space inside the walls and ceilings were much narrower than we had anticipated and several of those inside walls contained structural columns that occupied a lot of the space we had intended to use. In order to maintain the construction schedule and expedite the necessary modifications to the design, we built a partial BIM model to determine how to move forward. One of the new features to be included in the building was a four-pipe HVAC system. As the name implies, a four-pipe system uses four pipes in two self-contained systems, so there are two pipes (one for supply and one for return) for hot water and two more for cold water.

Fitting all the piping into Andover Inn’s tight space was a huge challenge because, at first glance, it seemed as though the system was entirely too big for the amount of space we had to work with. The BIM model, built using the exact dimensions of the existing building, allowed us to evaluate different options and, ultimately, find a way to fit this large HVAC system into the small building. Some modifications had to be made to accommodate the four-pipe system. We were forced to lower ceiling heights significantly in certain areas of the inn to allow for the additional pipes. Erland’s BIM Coordinator, John Cormier, said of the project, “I don’t think we could have

found a way to fit that four-pipe system into that building without the BIM model. We had to rework the layout so many times to ensure a perfect fit and I don’t see how we could have done that in the field and still maintained the project schedule. It would have taken too long and it still wouldn’t have been as precise as the plan we derived from the model.”

Lesson Learned – Utilize Available Technology EarlierBecause of the BIM model, our team was able to finalize a design that satisfied our client’s needs and fit the existing structure – solving the seemingly insurmountable predicament of fitting the four-pipe system into the building. But, it’s possible we could have avoided the problem all together. Even though we did not have access to the inn before construction began, we could have ascertained the building’s layout by performing a laser survey using a 3-D camera that sends out laser beams and produces 360-degree photo. It is unobtrusive and would have taken

about a day to complete. Then, we could have compared our findings to the design assumptions and investigated further to fill in gaps of information. For example, the laser testing will not provide information on what exists behind walls and ceilings, but we could have discerned that by using X-Ray technology, which would have given us the complete structural layout of the building. With that information, we would have discovered that our design assumptions were not perfect and amended them before construction began.

Even without destructive testing or X-Rays, we could have garnered a lot of information from just the 3-D camera photos. For example, many of the ceilings were not as high as we thought. Transferring the data from the 3-D camera to a BIM model would have showed us that there was very limited space between the ceiling on the first level and the floor on the second level. We then could have analyzed that information, seen the possibilities/

potential for problems, and managed our risk with more educated assumptions.

Measuring the Success of BIM ModelsErland recently completed two projects where a BIM model was created early in preconstruction. In both cases, the projects came in on time and on budget, with very happy clients. Both projects presented significant challenges and we believe that the BIM models hugely impacted the success of both.

Palomar Medical Technologies• – Burlington, MassachusettsFor Palomar’s new 130,000 square foot corporate headquarters building, Erland built a BIM model that was used primarily for clash detection. The building’s MEP systems support manufacturing, laboratory, and office space, so the clash detection ensured that all issues with fitting systems into the building were fixed in the model before construction began. Our model’s accuracy and detail allowed the plumbing subcontractor to completely prefabricate the building’s bathrooms – ultimately saving significant time. Currently, we are working with the client to convert the finished model into an electronic as-built that will be compatible with their Facilities Management System. At the end of the project, Erland’s team was able to return $1.5 million in savings to the owner – an unlikely outcome had we not used BIM.

Covidien Bedford• – Bedford, MassachusettsFor this 70,000 square foot renovation, Erland again used a 3-D BIM model to perform clash detections. The renovation included the addition of several lab and R&D spaces, which required all new systems within the building. Our BIM model helped us to carefully lay out all the necessary piping in precise detail before construction began. For this project, we co-

located, meaning that the person from each trade that was responsible for creating its model was onsite at the beginning of the project. This allowed us to sit together in one room as we combined the individual models to create the complete working model of the building. Co-location helped us to build and fix the model faster – in about a week and a half – so the project could start on time. Clash detections were done daily and problems were fixed immediately, resulting in a model so accurate, our subcontractors were able to prefabricate much of the ductwork.

Deciding early to use BIM and a laser survey, especially for renovation projects where as-built information is scarce, will only serve to help create a smoother and more successful project. Because the more you know before you mobilize for construction, the better the outcome will be.

About the AuthorsChuck Vaciliou is Vice President of Operations for Burlington, Massachusetts-based Erland Construction. He has been with Erland since its founding in 1977. Chuck has extensive knowledge of all aspects of construction management including design and constructability review; cost control procedures; federal, state, and local codes, ordinances, and permitting.

John Cormier joined Erland in 2005 as a Project and MEP Coordinator, bringing with him more than 20 years of construction industry experience. Since then, he has led a company-wide

effort to incorporate BIM into all of our construction projects.