The Forensic Work of Vitruvius

April 23rd, 2012

When you mention forensic investigations, many people think of television detectives and crime labs. Fair enough, but whether the subject is a homicide or a building failure, the fundamental aspect of a forensic investigation is not the often obvious result (a person is dead, or a building collapsed) but is the careful examination of physical evidence and the use of logic to determine the how and why.  That’s exactly what Vitruvius did in portions of Books II and VII of De Architectura (his “Ten Books on Architecture”). He attempted to diagnose how and why something failed and, furthermore, what to learn from that when designing new buildings so as to avoid similar failures.

The forensic investigations of Vitruvius are similar to a large part of what I do here at Simpson Gumpertz & Heger (SGH). As a result, at various times, I’ve realized a very direct parallel between my technical observations and conclusions and those of Vitruvius in his famous treatise. It’s both inspirational and humbling to think you’ve figured something out yourself and then realize that someone else had already figured it out over 2,000 years earlier! It’s kind of like having a really cool grandfather who always inspires you but who always knows more than you do, no matter how much you learn.

Late 1990s view of badly blistered plaster and peeling paint at the northeast interior corner of the Old State House, Boston. Photo: SGH

 The first time I realized a parallel between my forensic investigations and those of Vitruvius was in the late 1990s, when I was only a few years out of school and into practice. I was investigating severe, persistent blistering of interior painted plaster finishes in the Old State House (1748) in Boston.

 What puzzled people for a long time was that the severe damage to the interior paint and plaster occurred only in the northeast corner of the building, yet the exterior brick walls, the flashing and the slate roofing at that corner looked just as good and just as tight as on the rest of the building. Further, over the years, multiple attempts at repointing the brick and improving the flashings and roofing at the problematic northeast corner had failed to halt the interior problems.

 After investigating the problem, my colleagues at SGH and I found that the interior blistering and damage were due to a combination of factors that coincide at the northeast corner. One of these factors was that the building was largely shielded by taller surrounding buildings, except near the northeast corner, where the exposure is wide open to wind-driven rain from the northeast. (“Nor’easter” storms are common in Boston, particularly in the winter when exterior walls tend to dry to the interior.)

 Another prominent factor was that the interior finishes in the west half of the building, which had no damage, were constructed on wood furring, creating an air space and capillary break between the plaster and the exterior brick masonry walls that made the interior finishes in the west half highly tolerant of moisture in the walls. On the other hand, the walls in the east half of the building, which suffered persistent damage, were constructed with the plaster adhered directly to the exterior brick masonry. This lack of a capillary break and air space made the plaster in the east half of the building unforgiving and intolerant of incidental moisture in the brick walls, which then became inevitable.

Late 1990s view of the northeast corner of the Old State House, Boston, with scaffold in place for our investigation and testing. Photo: SGH

 In our report, we recommended installing the replacement plaster at the badly damaged northeast corner in the manner in which the plaster in the west half of the building was installed: over furring so as to create an air space and capillary break between the plaster and the brick and thus make the plaster more tolerant of the inevitable moisture in the old brick walls. Fortunately, the direct-adhered plaster in the northeast corner of the Old State House was so thick that it allowed room for creating an air space behind, while maintaining the interior plane of the plaster and its relationship to the wood trim.

 In our report, I quoted Vitruvius, who had learned the same durability lesson and made similar recommendations in Book VII, Chapter IV (“On Stucco Work in Damp Place. . .”) for preventing damage to interior plaster by constructing a vented air space between interior plaster and frequently damp exterior walls.

Just a few years ago (about a decade after our original investigation and report), the work was undertaken by the National Park Service in conjunction with a major rehabilitation designed by Tellalian Associates Architects and Planners and constructed by the Lee Kennedy Company. I was pleased to hear from colleagues at Tellalian and Lee Kennedy that our early investigation report was well read and much appreciated, and they had accepted and successfully implemented our recommendation of creating an air space between the plaster and the brick at the northeast corner. Thanks to their good work, the interior plaster and paint at the northeast corner have finally stopped misbehaving.

 In both cases (the Old State House and the advice provided by Vitruvius in Book VII), it was prudent to admit and simply accept that the walls would often be damp and install the plaster in such a way that it would be tolerant of the dampness. This very specific example also illustrates a much broader principle of designing for durability: Accept the inevitable, and design in a manner to accommodate it.

More on that in my next blog.

 

Uncategorized

What It’s Not About

March 2nd, 2012

Believe it or not, this blog, titled “In the Footsteps of Vitruvius,” isn’t really about Vitruvius (Marcus Vitruvius Pollio) the man or his built work (none of which is known to be extant) or his famous treatise (De Architectura, better known in English as The Ten Books on Architecture). Nor is it even about the construction of ancient Roman buildings per se. The title alludes to my being greatly inspired by the methodology of Vitruvius and attempting to use his forensic methodology to continue the hands-on studies of construction durability that he conducted over 2,000 years ago in the first century B.C. Essentially, I’m attempting to pick up in time where he left off.

Seventeenth-century image of Vitruvius presenting De Architectura to Augustus (Image: Wikimedia Commons).

Part of what Vitruvius did and set forth in his treatise De Architectura (mainly in Book II and to a lesser extent in Book VII) was to examine ancient Greek buildings and earlier Roman constructions (intact buildings, other structures and ruins in both high-style monuments and simple vernacular constructions) with a critical eye toward the original construction details. He then made deductions about which details and methods of construction have proven more durable and which have fallen to ruins, as tested by time and the elements.

Most important, he didn’t just catalog what he saw as either a success or a failure based on whether it survived essentially intact or not; rather, he deduced and diagnosed and described why some construction methods and details had proved durable over time and why others had not and had fallen to ruins. He then conveyed these findings in the form of firm, definitive design and construction recommendations for current and future generations (of architects, engineers and builders) on how to build more durably. Obviously, Vitruvius’s studies ended with the publication of his treatise and with his subsequent death in the first century B.C.

Vitruvius’s basic forensic methodology from over 2,000 years ago is still at the core of what my colleagues and I at Simpson Gumpertz & Heger (SGH) do today in our forensic investigations of building problems and failures, whether those failures are gradual, long-term degradations of historic materials on centuries-old historic buildings or sudden catastrophic collapses or other failures on newer buildings or structures. Making very careful observations of a building and thinking and reasoning about what you are observing (as Vitruvius did) are still at the very core of any forensic work and necessary in helping to find the root cause of why something failed.

Understanding why things have failed is essential both to restoring historic buildings thoughtfully and appropriately (“analysis before restoration” is a principle of conservation standards such as the Athens Charter for the Restoration of Historic Monuments ) and to understanding how to design and construct new buildings more durably, and hence more sustainably, today.

This blog draws heavily from a Rome Prize research project of the same name (“In the Footsteps of Vitruvius”) that I undertook at the American Academy in Rome in 2009-10, conducted largely on the scaffolding of buildings under restoration in Rome and northern and central Italy. My study buildings in Italy ranged from the first century B.C. (the time of the death of Vitruvius) to early 20-century Modernist architecture. It also draws from my work here in the U.S. over the past 17 years for SGH. Throughout these blog posts, I’ll draw from these observations, lessons and findings to provide an understanding of how buildings work and how they fail, and what we can learn from this knowledge today.

Uncategorized , , ,