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Material Challenges in Historic Buildings

WEDNESDAY, JUNE 7, 2017

By Robert J. Kobet, AIA


More items for Maintenance + Renovation

One of the basic tenets of sustainable design and development is the preservation and adaptive reuse of existing buildings. Some say the greenest building is the one that has not been built, putting additional credence on keeping existing buildings in use. This is a question near and dear to me because, while I have not worked on historic conservation projects per se, I have been involved in a number of renovations and repurposed structures that remain some of my most rewarding efforts.

Preserving and repurposing existing buildings is supported by most current green building rating systems. The U.S. Green Building Council’s “LEED for Neighborhood Development” and other LEED V4 building rating systems categorically reward efforts to preserve and reuse existing structures, including historic buildings. This is based in part on preserving the embodied energy in building materials used in existing buildings, as well as the environmental benefits of reducing the construction waste stream and keeping materials out of landfills. This is important in restoration projects as they often involve the subtractive process of removing layers of materials applied over the exterior and interior of the original building.

USCapitol, Public Doman, Flickr

To understand the building material challenges associated with historic buildings, one first needs to be specific about what they are trying to accomplish, as the terms are sometimes confusing and often used incorrectly.

Early ideological collisions between purists focused primarily on the authenticity of the building fabric and those interested in making very old buildings more energy, material and resource efficient have been reconciled through scores of successful case studies that have recognized the value of each.

Happily, preserving buildings is not uncommon. We resonate with “period pieces” and often seek out the qualities and attributes that make up the ambiance of older buildings. We intuitively appreciate a classic hotel lobby, restaurant/bar, concert hall or railroad station. Often this is because of the warm materials, detailing and craftsmanship. However, all of this takes on additional significance when the structures in question are historic buildings. To understand the building material challenges associated with historic buildings, one first needs to be specific about what they are trying to be accomplish, as the terms are sometimes confusing and often used incorrectly.

A Look at the Terms

Renovation or restoration means to make an object look like new. Renovation essentially means bringing back to a former position or condition. In renovation and restoring, final appearance is usually the most important goal. The building to be renovated is a point of departure for the project team’s imagination, something that is most often retrained by budget. The building itself does not place restrictions on the work to be done. The client and project team determine the most desirable period of the building’s life, and do whatever is necessary to return the building’s appearance to that period.

In renovation projects, there is leeway in material selection, sourcing, installation and related construction trade skills. In buildings that are repurposed, there may be a fusion of historic elements with modern or contemporary design motif and building system technology. There are few building industry challenges in renovations. However, a historic building that is significantly altered via renovation may lose its historic status or appeal to purists.

USCapitol, Public Doman, Flickr

It is important for renovators, restorers, preservationists and conservators to have a basic understanding of these categories beyond which the work often becomes nuanced as a matter of degree.

Preservation is most commonly used in relation to architecture and the built environment. It involves keeping a building from destruction and insuring the building is not irredeemably altered or changed. Consequently, preserving buildings places additional requirements on decisions pertaining to materials and the methodology or processes by which the work is accomplished. In preservation, the final appearance may not be the prime factor, but rather, the focus is on retaining the maximum amount of original building fabric. If possible, the same methods that first created the building are used or re-enacted. The Office of the Secretary of the Interior has devised strict requirements governing this type of work.

In conservation, the maximum amount of the original material is preserved in as unaltered a condition as possible. Any repairs or additions must not remove, alter or permanently bond/cross-link to any original material. All repairs or additions must be reversible and removable without affecting the condition of the original material now or in the future.

Conserving a building dictates all choices on how the work is done. Artistic license or material substitutions are not acceptable.

It is important for renovators, restorers, preservationists and conservators to have a basic understanding of these categories beyond which the work often becomes nuanced as a matter of degree. To what extent are the project and building materials truly authentic? What percentage of the work involves original materials, and how much is recreated using acceptable material ingredients and processes? Is it even possible or realistic to pursue a genuine preservation or conservation effort if the subject building is compromised structurally and in need of modern stabilization techniques and materials?

Consider this:

  • While it may be possible to avoid “un-historic” drywall by implementing a classic three-part “scratch, brown and finish” plaster system, finding trades willing to use horse hair in the mix are far fewer.
  • Matching any original paint color is possible using modern equipment, but using the same lead-based paint is not acceptable, however authentic it may be.
  • Reverting to, or retaining, annealed glass instead of tempered glass is probably not wise for safety reasons and may be illegal in response to modern safety codes
  • Sources for Belgian block pavers, which are seldom used anymore, may not exist, or the quarry that supplied the original stone may be exhausted.

Wright's Fallingwater

My two favorite historic preservation projects are Frank Lloyd Wright’s Fallingwater and the U.S. Capitol dome. The battles Wright had with the structural engineers engaged to keep the iconic house over the water fall standing are the stuff of legend. In spite of Wright’s insistence that the structural design was adequate, the main level cantilever sagged perceptively—about 1¾”—as soon as the supporting scaffolding was removed. This even after the workers doubled the amount of square rebar that was specified in the four main supporting beams. It continued to sag over the years, resulting in visual structural cracks and a deflection of seven inches.

Courtesy of the Western Pennsylvania Conservancy

In spite of Wright’s insistence that the structural design was adequate, the main level cantilever sagged perceptively—about 1¾”—as soon as the supporting scaffolding was removed. This even after the workers doubled the amount of square rebar that was specified in the four main supporting beams.

In 1995, the Western Pennsylvania Conservancy engaged Robert Silman Associates of New York to examine what had become obvious structural problems. The $11.5 million-dollar rescue project to a home that originally cost $155,000 involved modern analytical technology and equipment to install multiple steel cables to re-tension the existing reinforced concrete beams. The deflection was not corrected, only arrested in place, telling the true story of a house over a water fall that was on its way to collapsing into the stream below.

Before the structural repairs began, over 600 of the original stone floor tiles were mapped, removed and stored on site for replacement after the structural repairs were complete. Additional work was also done to waterproof the flat roofs to try to stop another one of the problems typically found in Wright’s designs—chronic leaking.

The Capitol Dome

The U.S. Capitol dome project was chronicled in a November Durability + Design News article that discusses some of the many materials and processes used to repair the largest and most iconic cast iron dome in the world.

The $60 million project was a joint venture between Turner Construction Co. and Smoot Construction, the lead contractor. Each worked directly with Architect of the Capitol, Steven D. Ayers, FAIA, whose office oversees the structure.

Like Fallingwater, the Capitol dome was exhibiting a disconcerting collection of over 1,000 cracks and deteriorating structural connections that were aggravated by chronic water leakage. Numerous rosettes and ornamental objects were also in serious disrepair. Much of the surface preparation, lead abatement and coating work was performed by Medford, Orgeon-based F.D. Thomas, who also took part in the onsite repair of the cast-iron pieces, a process that utilized the Lock-n-Stitch and “Dutchman” techniques.

The paint on the dome was applied in three coats of about 405 gallons each. The top coat of fluropoloymer was applied over epoxy primer and Macropoxy 646 mid coat. The top coat, called “Dome White,” was engineered to withstand the elements and shed dirt.

On the interior of the rotunda, the wood and iron were painted with two coats of Benjamin Moore Eco Spec water-based latex paint on top of one coat of its commercial brand Corotech alkyd primer.

The offsite restoration of cast iron components, including the creation of replica ornamentation to replace ornaments that had broken, was done by Historical Arts and Casting, of Jordan, Utah. The project also required the artwork inside the cupola, as well as visitors down below, to be protected, which contractors did by installing coverings, including a donut-shaped protective canopy, inside the dome.

Together these projects represent what I believe is the most common approach to renovation and preservation projects—a mixture of authentic reproductions, modern materials and craftsmanship that respects the history and iconic significance of both structures. In each case, true conservation was not possible; innovation and modern materials were required. I’m just happy they will continue to be visited, admired and appreciated by people around the world.

ABOUT THE BLOGGER

Robert J. Kobet, AIA

Robert J. Kobet has worked with clients on five continents for more than 35 years to create innovative places to live, work and learn. As an architect, educator, speaker, former chair of LEED for Schools, primary author of LEED for General Contractors and Construction Managers, and president and CEO of The Kobet Collaborative, Bob is working to make his vision for a green building era a reality. Leaning Green explores that reality. Contact Bob.

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Tagged categories: Architecture; Historic Preservation; Renovation

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