Copper roofing restoration work provides low-maintenance protection for thousands of rare books
During the summer of 2015, Harvard Law School‘s Library Blog notified students that noise-canceling headphones and earplugs would be available for checkout. It may seem like an extreme measure to ensure a quiet library, but for a few months the world’s largest academic law library underwent a major roof replacement to revitalize its iconic neoclassical building named after Harvard’s first dean of the law school, Christopher Columbus Langdell.
The Cambridge, Mass.-based school erected Langdell Hall in 1907 to hold its massive academic collections; the northern and western wings were completed in 1929. Although a significant interior renovation was completed in 1997, including mechanical systems upgrades and accommodations for present and future technology needs, extensive repairs to the roof and limestone parapets were needed to address damage and leakage that had occurred over the years due to cracked mortar and inadequate drainage.
The roof restoration construction included the replacement of multiple types of roofing systems, including built-up, metal standing seam and PVC membrane and significant parapet flashing. The new roofing system included both standing seam and flat seam copper panels to replace existing copper panels and to maintain the historical integrity of the original design.
Standing seam roofing is typically composed of preformed or field-formed pans, usually 14 to 18 inches wide when finished; however, dimensions may vary based on the project. These pans run parallel to the slope of the roof and are joined to adjacent pans with double locked standing seams. Fixed copper cleats lock into these seams to secure the roofing to the deck.
Flat seam roofing systems, on the other hand, are typically used on roofs that are flat or have a low slope. They are also used on curved surfaces such as domes and barrel vaults. The roof is constructed of 18 inches by 24 inches, 20-ounce rectangular cold rolled copper sheets. Two adjacent sides of the sheets are folded over and two are folded under to form 3/4-inch locks. Copper cleats of 16- or 20-ounce cold rolled copper are installed in each of the longitudinal and transverse seams. The finished pans are interlocked longitudinally and transversely, with staggered transverse seams.
Before the roof installation took place, the design team created and reviewed a mock-up installation of the copper. The mock-up included all details that would occur in on the project. All sheet metal workers were required to complete an installation test, which is a step above and beyond most typical roof installation projects. The envelope consultant approved each worker prior to starting the project.
The new copper panels were 22-gauge thickness, in lengths varying from 19 and 5 inches to 9 feet and 10 inches, 20 ounces per square foot. Standing seam height was 1 1/2 inches, with 20 3/4-inch panel width (standing seam to standing seam) with exposed mill finish. Approximately 1,400 linear feet of zinc-coated copper, also known as Freedom Gray, parapet coping cap, was installed at the perimeter.
A total of 24,750 pounds of copper and 0.8 acres of PVC rubber were installed over the expansive Langdell Hall roof, which is located in the heart of Harvard Law School’s campus and adjacent to Cambridge’s historic district. The project was completed in four phases to comply with the City of Cambridge’s historic codes. The new covering is expected to protect the library collection of more than 2.3 million volumes and 300,000 rare books for many years to come. When properly installed, a copper roof provides an economical, long-term roofing solution. Its low life cycle costs are attributable to the low maintenance, long-life and salvage value of copper. Unlike many other metal roofing materials, copper requires no painting or finishing.
Historically, copper has long been used because of its great natural beauty and finish, its performance and durability, and its long service life and recyclability. Today, copper remains a superior building material, adapted and utilized for a wide variety of contemporary and cutting-edge applications.
The Harvard Law School Langdell Hall roof replacement project design team received the coveted North American Copper in Architecture (NACIA) award in 2016 for their craftsmanship, attention to detail and architectural vision. The annual program, offered by the Copper Development Association (CDA) and the Canadian Copper and Brass Development Association (CCBDA) recognizes and promotes North American building projects for their outstanding use of copper and copper alloys. The winning projects are selected from among three different categories-New Construction, Restoration/Renovation and Ornamental Applications.
Langdell Hall, Harvard Law School, Cambridge, Mass.
Owner: Harvard Law School, Cambridge
Architect: Baker | Wohl Architects, Boston, www.baker-wohl.com
General contractor: Consigli Construction Co. Inc., Milford, Mass., www.consigli.com
Roofing contractor: Titan Roofing, Springfield, Mass., www.titanroofing.com
Envelope consultant: Simpson Gumpertz & Heger, Waltham, Mass., www.sgh.com
Copper manufacturer: Hussey Copper, Leetsdale, Pa., www.husseycopper.com
Photo: Mathew Kuzmik
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Stephen Knapp is the program manager of the Sheet, Strip, and Plate Council for the Copper Development Association Inc., and the executive director of the Canadian Copper
& Brass Development Association. He also is involved with guiding the market development and promotional efforts for a wide variety of copper and copper alloy applications. To learn more about copper applications and to learn about other NACIA award winners, visit copper.org.