As new development encroaches on existing cities and sites—making older cultural resources more precious than ever—advances in technology can give architects a step up in terms of preserving historic buildings. This is particularly true in cases where buildings have survived, but their building documentation has not.
Until recently, architects had to rely on physical surveys, building records, and guesswork to piece together information about inaccessible locations. That all has changed with the application of laser scanning to large-scale structures, which is revolutionizing documentation of historic sites. Besides being faster, it also is noninvasive and highly accurate.
In a real sense, laser scanning opens doors: architects can use this tool to gather data from buildings in such poor structural condition that they’re not even safe to be inside. The amount and quality of data gathered also can facilitate lengthy review processes and help keep multiphased projects moving forward. Finally, laser scanning technology can save time and money—factors that are of considerable importance to any project.
What are the benefits?
• Increased accuracy of base information
• Data formatted for easy conversion into a 3D model of existing fabric and coordination of elements such as new building systems
• Production of accurate construction sections, plans, and details
• More accurate quantity surveys leading to more accurate cost estimates
How is it done?
The laser scanner rotates a full 360 degrees and captures data in what’s known as a “point cloud.” Even with the scanner, it usually takes several scans to document each building or room. These point clouds are then fused together and processed with customized software to create a virtual model that can be manipulated with CAD software.
As a next step, point clouds are translated into 3D modeling software, such as Revit, so the design team can create Building Information Modeling (BIM) models of the buildings that can be shared with contractors for estimating, phasing, and coordination. It promotes better coordination between building systems (mechanical, electrical, and fire protection) that are vying for limited space and improves estimates through accurate quantity surveys.
All this points out that the pace of development in drawing technology seems to grow exponentially. In fact, the change from two-dimensional drawings on Mylar to BIM took less than two decades. What has not changed is the need for accurate, timely, retrievable, and sharable information so that all members of the building team—owner, architect, consultants, and contractor—can understand design intentions, save historic properties, and work together to create successful projects.
Case Study: St. Elizabeth’s Hospital
One of the first and largest rehabilitation projects to make extensive use of laser scanning is the St. Elizabeth’s Hospital campus in Washington, D.C., which opened in 1856 as the country’s first federal asylum. In 2004, St. Elizabeth’s West Campus was taken over by GSA for use as the headquarters of the Department of Homeland Security. The East Campus continues to be operated as a mental health facility by the District of Columbia.
Laser scanning (shown below) allowed Farewell Mills Gatsch Architects to create measured drawings as a basis for the large-scale rehabilitation project. This was necessary because the campus—which covers more than 160 acres and has more than 60 buildings—was in a considerable state of disrepair.
At the outset of the project, the GSA wanted to learn what resources still existed in this National Historic Landmark resource. While there was a huge amount of material about the buildings—in text, drawings, maps, and photographs—it quickly became clear to the GSA that the information was not comprehensive or organized. Most importantly, there were no reliable plans for the buildings.
In the past, recreating the original plans might have been an insurmountable task. Instead, GSA used laser scanning to produce full building plans for all the buildings at St. Elizabeth’s that had historic significance. The plans offered the first accurate estimate of the buildings’ sizes and provided the master planning team with the ability to study the proposed redevelopment in view of the existing structures.
Beyond the redevelopment, the data allowed the team to produce the historical and graphic documentation that is required for regulatory approvals from the National Capital Planning Commission and the Commission of Fine Arts. It is currently helping GSA and DHS to pass through a consultation and approval process with the Advisory Council on Historic Preservation.
Anne E. Weber, FAIA, is a senior associate with Farewell Mills Gatsch Architects in Princeton, N.J. During her 27-year career, she has concentrated on managing large-scale institutional historic preservation projects. Her recent notable works are the restoration of the Essex County Courthouse, the Princeton University Chapel, and life safety improvements at the Statue of Liberty.