Repairing and Restoring Historic Roofs

• By Ellen Kollie
• 11/01/07

Historic buildings are an asset to a campus, speaking to an institution’s rich legacy of education. They add character to a campus setting while serving as flagships. To maintain these qualities, it’s critical that historic buildings be well preserved. The roof system is an important component of that preservation, as it protects all of a building’s internal systems.

Repairing and restoring historic roofs involves two major elements: materials and maintenance. Here’s an explanation of how to manage both for the best possible outcome.

An excellent place to begin resolving a roof challenge on a historic building is with an architect who specializes in historic facilities. Many reasons can be given for this, but the most compelling is that a historic roof may look and act like it needs replaced but, in fact, only needs repair. Paying for an analysis is well worth the savings gleaned from repairing as opposed to replacing.

If replacement is needed, the good news is that facility managers can choose from historic materials like copper, slate, and tile, or from contemporary materials like asphalt shingle. There are even imitation materials available, designed to look like historic materials, which may be worth investigating as roofing solutions.

For example, rubber is being recycled into a roofing product that looks like slate.“At first appearance, it looks good,” said Michael J. Mills, FAIA, partner in charge of preservation for Princeton, NJ-based Farewell Mills Gatsch Architects, LLC, and vice chair of AIA’s Historic Resources Committee.“However, it doesn’t weather like slate. Still, it’s a creative use of recycled rubber, and looking for environmentally responsible roofing products is a good thing.”

If it’s important to replace the roof with the same material that was originally used, know that that material is available from a manufacturer somewhere. Finding it may involve some research and talking with manufacturers about their capability to match size and shape and do custom orders. “To say that the material is no longer available is simply not valid,” said Elizabeth Corbin Murphy, FAIA, principal of Akron, OH-based Chambers Murphy & Burge Restoration Architects, Ltd., and a member of AIA’s Historic Resources Committee. “There has to be another reason to change from the original to something else.”

When considering the use of contemporary materials — like asphalt shingle — evaluate the life-cycle cost, and not just first cost. The explanation is that an asphalt shingle roof will be replaced at least three times before a slate roof will need to be replaced, making long-term costs much higher. “We did life-cycle costing for a client who chose to put slate on the roof of a historic building,” said Murphy. “The original slate roof had been replaced with asphalt shingle, and the client saw the value in returning to the slate to minimize future costs and maintenance.” He cautions that not every project turns out that way, but strongly recommends that facility managers look at longevity as part of the initial capital expense.

Another thing to consider when doing a complete replacement is the history of the building. “Each building has its own history,” said Jack Pyburn, FAIA, principal and director of Atlanta-based Lord Aeck Sargent Architecture’s historic preservation studio. He notes that it’s not always a straightforward exercise to choose to use the original material. For example, a facility may have been built in 1840 and modified in 1900, including a different roof material. If a person of renown used the building after 1900, it might have become more significant to the university after 1900 than it was before. In replacing the roof today, it’s important to choose the material according to what existed during the facility’s period of significance.

A final thing to consider when doing a complete replacement is the historic appearance. If a material is chosen that is not the original, the appearance of the building is dramatically changed, said Mills. This is a critical consideration if the building is on the National Register of Historic Places.

Murphy agreed, noting that, “if all the buildings on the campus were built at one time and all the roofs are the same, then replacing one roof with a different material results in the entire campus losing integrity. This doesn’t mean roof materials should not be changed. It does mean you really have to think about it before you do it.”

Once you invest in either a new roof or repair of an existing roof, the key to its effectiveness and long life is maintenance. This is sound advice for facilities of any age. “The best warranty on a roof is a good job,” said Pyburn. “You want to see a good roof system, well detailed and well executed. Then, you must systematically monitor it and respond to it as it ages through time.”

Clean the gutters at least once a year. The experts in this article recommend cleaning them two or three times a year. “Maple leaves and pine needles, if they start to rot, can create acids that eat away at the gutters,” said Murphy. Clean gutters prevent this, as well as icicles and ice backing up underneath the roofing material. Also check the flashings, that water drainage is effective and working well, and that you don’t have accumulating bird waste.

Inspect the roof at least once a year to see if there’s damage from severe weather like hail or wind storms. This may require a qualified contractor. “For example, a qualified slate person may be needed to crawl over a slate roof,” said Mills. “That person also can repair slate that is cracked, broken, or slipped, as well as make sure roof is well secured.”

Every time a roof is inspected, be sure to take notes about what is found. In this manner, when a small deterioration is discovered, it can be continually observed and a repair made before serious damage occurs.

By far the most important part of maintaining a historic roof is a maintenance budget. “It allows you to keep up with small challenges,” said Mills, pointing out that occasional repairs are much more affordable than an entire roof replacement.

While facility managers have been so busy maintaining and preserving historic buildings on their campuses, facilities built in the late 19th century and through the first quarter of the 20th century have been maturing. Many will be classified as historic.

For these facilities, low-slope roofs are the norm. Pyburn notes that there is a bit of a bias against low-slope roofs, which puts pressure on historic buildings to have an inappropriate roofing profile and system.

“I wish there was a greater comfort level for building managers in well-designed, well-installed, low-slope roof assemblies,” expressed Pyburn. “It comes back to the fact that the best warranty is a well-installed and well-maintained roof.”

Perhaps some day, Pyburn’s wish will come true.