3D Laser Scanning Gives 1960s Office Building a New Lease on Life

by Balfour Beatty
Accurate as-built data is a critical component of any planning and design process – a fact that rings especially true in the realm of adaptive reuse projects. For buildings that were originally constructed decades or more ago, like so many in the metro-Washington D.C. area, the little data that is available is often inaccurate.

That’s precisely why Balfour Beatty’s Mid-Atlantic team has utilized laser scanning instead of traditional surveying on the first phase of their work at Hoffman Town Center in Alexandria. When the project team considered how to approach the renovation of a 348,000-square-foot, 1960s era office building in the development, laser scanning was the obvious choice to obtain an exact digital reproduction of existing conditions.

Though the project team knew laser scanning would reap tremendous benefits before construction even began, the details they uncovered didn’t just save time and money – they were absolutely critical to the project’s success. First, they discovered a pervasive deviation in the floor plates. The plates, which should have stacked right on top of each other, were misaligned approximately ½ inch from one floor to another. The laser scan also revealed floor-to-floor elevation issues. In any 25-foot column base, the elevations varied from ¾ inch to 2 inches in floors that should have reached an exact 10 feet, 2 inches. This discovery allowed the team to not only identify floors for selective leveling but also make adjustments in the precast to ensure design integrity of the window openings.

“Even after extensive demolition, not all of these building deviances were visible to the naked eye,” said Sam Brownfield, senior TPD specialist. “Instead of making assumptions about what conditions may or may not have existed, we were able to learn with absolute certainty how to achieve the best result for the owner.”

The floor plate and elevation issues were important discoveries, but there were more surprises lurking in the aging structure. Through the laser scan, the project team learned of a final building anomaly: one side of the building was actually “skinnier,” meaning some of the floors were narrower on one side than the other. This enabled the project team to be proactive and design for and accommodate those deviations within the supports for the precast and metal panels versus being in a reactive mode during fabrication and installation.

“Throughout my career, I’ve found that every job comes with its own set of surprises. The key is being one step ahead, and with a 3D laser scan, you’re ten steps ahead,” said Dave Jones, project executive. “It’s one of the best forms of quality control you could ask for.”

With the success of the structural scan behind them, the project team is currently utilizing software from Trimble known as RealWorks to determine the above-ceiling mechanical systems layout. Because of the building’s narrow floor plates, VAV boxes can only fit in very precise locations. With RealWorks, Balfour Beatty can pinpoint precise locations for the VAV boxes while providing subcontractors with an exact grid pattern in a CAD file to enhance collaboration. RealWorks also enables the team to continue developing the floor leveling scope within a given finish ceiling height.

“While new construction may have once been the norm, the concept of repurposing old buildings is here to stay in an area as historic and sustainably-minded as Washington D.C.,” said Dave. “People want to live in urban areas where old buildings are kept and reused, and laser scanning is going to help them do that.”