18th Century Building Poses Restoration Challenges

Staff | September 28, 2010

The three-year restoration of the historic Single Sisters House on the Salem Academy and College campus in Winston-Salem, North Carolina, has been completed, thanks to a lot of careful planning and creative problem-solving. The result is a building modernized for today's use as office and meeting space as well as a museum that will be open to the public in fall 2007. The museum illustrates Moravian life — particularly for girls and women — in the 18th and 19th centuries.

Frank L. Blum Construction Co.'s expert craftsmanship and attention, along with Marianna Thomas Architects of Philadelphia, has resulted in a restoration true to the history of the Sisters House, built in 1785 to serve as the residence and business headquarters of unmarried Moravian women in the town of Salem. However, it also offers modern amenities such as air conditioning and high-speed Internet access — with equipment expertly and creatively concealed throughout the three-story building. Along the way, there were many challenges and a few surprises.

One challenge was repairing the deteriorated mortar joints in the brick walls. A Blum employee traveled to a lime putty workshop offered by the U.S. Heritage Group in Chicago, Ill., where he learned how to mix water, lime and sand into a putty-like mortar, just as the Moravians did. U.S. Heritage analyzed the mortar in both the original 1785 building and the 1819 addition so that the ingredients could be exactly matched in each section, down to the same color and size of sand granules.

During the restoration of what is now a museum section, exposed brick pavers inside the building were taken out and numbered so that they could be set back in their original locations.

Although Blum expected to make significant repairs to the roof, the extent of water damage was a surprise, said Tom Brown, the Single Sisters project manager for Blum Construction. "There were many leaks that had allowed water to infiltrate the roof, particularly around the dormers, and this had led to significant deterioration of the oak timber rafters and the pine plank sheathing."

Repairing the roof structure posed an unusual challenge. The clay tile shingles were overlapping, so they had to be taken off in 30-foot sections from the top down. If Blum removed a section from the west side, an equal section had to be removed from the east side at the same time to keep the fragile roof timbers from buckling and causing the entire roof structure to shift to one side or possibly collapse.

A heavy timber framer who is an expert in 18th century construction came to Winston-Salem from Pilot, Virginia, to help Blum develop a strategy for repairing the roof structure. Instead of using glue and nails, the Moravians had attached the sloped oak timber rafters to the horizontal timbers of the third floor with wood dowels using a mortise-and-tenon joint, a popular technique of the 18th century. The Blum crew carefully replaced the damaged pieces using the same method. They also added a waterproof membrane barrier, with additional overlapping stainless steel flashing, to protect the roof from future water damage.

About 80 percent of the clay roof tiles were in good enough condition to be put back on the building, but new shingles had to be specially created and manufactured to blend in with the old ones. Although the new tiles are a beautiful, historically faithful recreation, they are different in an important way. Unlike the brittle, feather-light original shingles, the new clay ones weigh 4 pounds each. Blum carefully mapped out how to place the shingles back on the roof in a way that would evenly distribute the weight and color.

Because the building will house assembly rooms and offices as well as serving as a museum, modern electrical and heating and cooling infrastructure had become necessary. However, unlike a modern office building, there is no one place in the Sisters house that can serve as the equipment hub for the entire building. Instead, elaborate ductwork is now located throughout the building in unseen spaces hidden behind the historic plaster walls. Mechanical rooms were tucked into spaces in the basement and attic as well.

The restoration also revived some historic features that had been hidden by renovations over the years. The Moravians added to the 1785 structure in 1819. A corridor running the length of the building was added in 1841, which covered up some original doors. Using research and drawings done by Marianna Thomas Architects, Blum exposed some of these to view. Patches of plaster were left unpainted in several places to show graffiti written by the young girls who lived there so long ago.

Although Blum is no stranger to renovations on the historic Salem campus, having successfully completed numerous modernizing projects to residence halls, the Sisters project was one of its greatest challenges to date. "This project shows the careful planning, attention to detail and pride in workmanship that Frank L. Blum Construction Co. is known for," said Drew Hancock, president of Blum. "We are proud and honored that we were chosen to restore the oldest building on any college campus in North Carolina."