In my capacity as a historic preservation contractor and consultant, I am often afforded the opportunity to become involved in exciting and challenging projects. Recently, we were awarded the contract to restore the clay tile roof turrets at the Longy School of Music’s Zabriskie House. Now a part of Bard College, the Zabriskie House is actually the historic Edwin H. Abbot House with a sympathetically designed addition built in 1969-70. The deteriorated condition of the turrets, as well as lead-coated copper gutter linings and masonry dormers, had attracted the attention of the Cambridge Historic Commission and a commitment to the proper restoration of these systems was struck between the CHC, building owner and a private donor.
Before I can specify historically appropriate treatments, I need to don my consultant’s cap and dig into the history of a building to best understand its evolution. Developing the background story will typically answer questions and fill in the blanks when examining traditional building systems. An 1890 newspaper clipping held by the CHC reports that “[t]he stately home of Mr. Abbot, with its walled-in grounds, on the site of the old Arsenal, promises to be the most costly private dwelling in the city.” An examination of records held by the Massachusetts Historical Commission and from the Library of Congress’ Historic American Building Survey reveal that the firm of Longfellow, Alden and Harlow designed the Richardsonian Romanesque portion of the building and that Norcross Brothers was the builder of record.
Alexander Wadsworth Longfellow, Jr., was the nephew of the famous poet and an important figure in architectural history of the United States. After graduating from Harvard University in 1876, he studied architecture at the Massachusetts Institute of Technology and the École des Beaux-Arts in Paris, after which he worked as a senior draftsman in Henry Hobson Richardson's office. After Richardson's death in 1886, Longfellow partnered with Frank Ellis Alden and Alfred Branch Harlow to found the firm of Longfellow, Alden & Harlow. With offices in Boston and Pittsburgh, the firm designed many important buildings including the Carnegie Library of Pittsburgh and the City Hall in Cambridge, Massachusetts.
Norcross Brothers Contractors and Builders was a prominent nineteenth-century American construction company, especially noted for their work, mostly in stone, for the architectural firms of H.H. Richardson and McKim, Mead & White. Following the death of Richardson, the brothers became the contractor for many of McKim, Mead & White's projects. As had been the case with Richardson, much of the value of the Norcross Brothers to architectural firms derived from Orlando Norcross's engineering skill. Though largely self-taught, he had developed the skills needed to solve the vast engineering problems brought to him by his clients. For example, the size of the dome at the Rhode Island Capitol was expanded very late in the design process, perhaps even after construction had begun, so that it would be larger than the one just completed by Cass Gilbert for the Minnesota Capitol.
The Edwin Abbot House is an interesting interpretation of the Richardsonian Romanesque style. Whereas the great majority of such buildings feature rusticated, pink Milford granite in an ashlar pattern, trimmed with East Longmeadow brownstone, Longfellow created a unique spin for Mr. Abbot. While trimmed with the brownstone, the field of the walls features coursed Weymouth granite of slightly varying heights. The motif of orange, brown and golden hues of the stone is continued in the brick wall surrounding the property. The roof is covered in a flat, square orange-red clay tile. This is typical of Richardsonian Romanesque buildings which are almost exclusively roofed in clay tile, Monson black slate, Granville, New York, red slate, or some combination thereof. It should be noted that because their need for stone was outpacing the supply, Norcross Brothers eventually acquired their own quarries in Connecticut, Maine, Massachusetts, New York, and Georgia.
The roof framing system of steel and terra cotta blocks is relatively rare but makes perfect sense when considered in context with what the latest flooring technologies of the era were. A network of steel beams was bolted together to form the rafters, hips and ridges of the frame. Across each was welded rows of double angle irons (or, inverted T beams.) Within these channels, in beds of Portland cement, was laid the terra cotta block. The tile were then fastened directly to the blocks with steel nails. Because of the ferrous nature of the fasteners, the normal passage of moisture vapor caused the nails to rust and expand slightly, anchoring them securely in place. Whether this element of the design was intentional or simply fortunate happenstance, the result made for a long-lasting roof.
What doesn’t last forever in traditional roofing systems like slate and clay tile is the sheet metal flashing assemblies. Over the years there must have been numerous failures which lead to the decision to remove the clay tile from the broad fields of the roof and replace them with red asphalt shingles in the 1980’s. Confronted with the dilemma of securing the new shingles to the terra cotta substrate, a decision was made to sheath the roof with plywood. Holes were punched through the blocks and toggles used to fasten plywood to the roof. In an area where the asphalt shingles were removed, more than 50% of the plywood exhibited varying degrees of rot due to the normal passage of vapor from the interior spaces.
Fortunately, the turrets had survived the renovations from thirty years before. A conical turret, in the rear, and an eight-sided hip-roofed turret on the north sided required only repairs which, while extensive, did not require addressing issues with the substrate. The sixteen-sided turret, on the primary façade of the building, was in poor condition. Over the years, prior “repairs” included the use of non-matching tiles, red roofing cement, tar, caulk and even red slate. A scaffold was erected to allow safe, unfettered access to the entire turret and the process of removing the tile began. Care was taken to conserve as many as possible for use in repairing the previously described turrets.
The substrate was examined closely and, save for thousands of tiny craters created by the original nails, found to be sound. A new system had to be devised that could be attached to the terra cotta blocks, allow for the replacement tiles to be securely fastened and resist the damaging forces of escaping moisture vapor. Cement board, comprised of 90% Portland cement and ground sand, was fastened to the blocks with ceramic-coated masonry screws. The entire turret was then covered with a self-adhering membrane. The replacement tiles were carefully matched and sourced from a salvage dealer in Illinois and secured with stainless steel fasteners. The flat tiles, no longer manufactured new, are referred to as “Cambridge” tiles for their prevalence on the roofs of great homes and institutional buildings in and around Cambridge, Massachusetts.
While I typically advocate for the retainage of all historic fabric when preserving and restoring traditional building systems, there are exceptions. In the case of the Abbot House roof, we encountered “modern” technologies which pointed us toward contemporary means and methods. Rusting steel nails in the terra cotta block was brilliant for initial installation but seemed ill-conceived for a second go around. Use of non-ferrous fasteners and a new substrate that is impervious to moisture infiltration will guarantee the turret’s new service life for the next 125 years or more. Contact us today by clicking here.
When the time is right: Appropriate use of modern materials in a traditional roof system
Is Greener Always Better? Problematic Use of Modern Materials in Traditional Building Systems
When new words and terminology enter our vernacular, they often take on a connotation larger and broader than they deserve. Today, “green” and “sustainable” are synonymous with responsible living and construction, their meanings understood as clearly by an architect or engineer as they are by the lay person. They are buzz words that make consumers feel good about their purchases; they’re doing their part to protect the environment and help save the world. But, in certain applications, use of these terms is more than a misnomer; it’s outright false advertising.
Do you care about historic buildings?
Proposed changes to the International Energy Conservation Code threaten to cause irreparable harm to thousands of historic buildings in the United States. I refer you to “International Code Council Approves Stringent New Requirements for Historical Structures” from Architect magazine.
When I recently attended the Massachusetts Historic Preservation Conference the first session I signed up for sounded enticing: Current Challenges in Applying the Secretary of the Interior’s Standards for Rehabilitation. The blurb in the program mentioned what you’d expect about how the “Standards for the Treatment of Historic Properties promote consistent and responsible preservation practices and help to protect the historic features that define the character of significant cultural resources.” It went on to advertise that expert panelists would present case studies that dealt with the challenges of adaptive re-use: energy efficiency, sustainability, code compliance, and accessibility. ‘Sign me up,’ I thought, ‘this is what I’m all about!’ The repurposing of existing buildings for new or continued use is the most important issue on the horizon of the built environment today. And preserving the “historic features that define the character of significant cultural resources” is a challenge close to the heart of those engaged in such endeavors.
Historic fabric is a term used quite regularly in the historic preservation world but what it is, or—better—how it comes to be, receives disproportionately little attention. McGraw-Hill’s Dictionary of Architecture and Construction defines historic fabric as “those portions of a building fabric that are of historic significance.” This definition implies that materials that are part of a building develop significance, presumably over time and as it relates to the life of the building. One might also infer from the definition that some parts of a building may not possess historic significance. What other sources provide a definition for historic fabric? It would be ideal to point to a definition supplied in the Secretary of the Interior’s Standards for the Treatment of Historic Properties but one does not exist. Surprised? There’s no definition of historic fabric in the National Park Service’s Cultural Resources Management Guideline’s glossary either.
Assessing and prioritizing a building’s needs, planning for work, hiring and supervising contractors, and then maintaining the systems of the building in a good serviceable condition is part of a systematic process. The first step is a conditions assessment performed by an architectural historian or qualified historic preservationist. The systems of the building and causes of deterioration are identified, historically appropriate treatments are specified, the work is prioritized, and a construction budget is generated.
While the internet may be a fantastic tool for sharing information, we must realize that good advice is transmitted as easily as bad. Consider this recent dialogue from a historic preservation message board in New England. An architect asked, “Has anyone had experience with use of cellular PVC to ‘replicate’ architectural details on a historic building?”
About the author
Ward Hamilton is a recognized expert in historic preservation and the owner of Olde Mohawk Historic Preservation. He provides consulting and contracting services to clients in Greater Boston and throughout New England.