Born-again cathedral

Masonry Construction, May, 2003 by Diana Granitto

Built of Sewanee sandstone and trimmed in Bowling Green limestone, the Christ Episcopal Church has weathered the elements for more than 100 years on the corner of 9th and Broadway in Nashville, Tenn. The main church was built in 1894, six years after the adjacent original chapel, which is now a parish house. Since that time, the buildings have been continually assailed by deposits from the coal-burning furnaces used in Nashville until 1960, from the locomotives frequenting nearby Union Station, and from vehicle emissions coming from nearby thoroughfares.

Thus it was fitting that the church, which is listed on the National Register of Historic Places, should undergo a facelift as it entered its second century. A close examination revealed that the sandstone was compromised by decades of relentless emissions and by early restoration attempts that might have used sandblasting or heavy chemicals. In addition, the mortar was so deteriorated that the entire building would have to be repointed.

The first step for restoration contractor WASCO Inc. was to determine whether the sandstone could be treated with a stone hardener. "You could just take your hand and rub off pieces of the stone from the face," said project manager Dallas Upchurch. "The original pitched-face texture was gone."

WASCO worked with PROSOCO, the consolidation treatment manufacturer, on the project. The manufacturer lab-tested 1 1/2-inch cores and found that it was feasible to apply one of its silicon dioxide pretreatments for friable substrates on the sandstone.

After removing the loose sandstone and cutting out the joints, the restorationists applied the pretreatment in three applications of three cycles each, followed by curing periods. A crew returned later to patch the damaged stone using a Cathedral Stone Products' cementitious, mineral-based material. Workers then tuckpointed the stone with a lime mortar. After allowing it to cure for up to two weeks, the crew lightly cleaned the stone once more. Finally, after all the treatments had dried and cured, the workers applied about 1200 gallons of a natural stone treatment to provide long-term water resistance.

Because of the numerous cycles of product applications and curing periods, WASCO expected the restoration to take about two years. "Luckily, we had a real mild winter," said Upchurch, "and the company's crew of eight to ten workers tended the $420,000 project for just over one year."

Project Participants

Restoration Contractor: WASCO Inc., Nashville, Tenn.

Suppliers: PROSOCO Inc., Lawrence, Kan. and Cathedral Stone Products, Hanover, Md.