Preserving a piece of history: scaffold design helps protect masonry in a historic courthouse restoration - restoration

Masonry Construction, Dec, 2002

Texan pride is legendary. This deep-rooted sense of legacy is attributed to the area's unique history that dates back to the 1700s and early Spanish colonization. And when it comes to remembering Texan history, it's no more important than in San Antonio.

While thousands of visitors share the story and bravery of the soldiers at the Alamo, the city also has a second important structure that its citizens look upon with another link to history.

The Bexar County Courthouse was completed in 1897 and in some respects is considered an important historical link in Texas history. According to research conducted by Sylvia Anti Santos, the four-story structure is "the direct heir of the oldest municipal government agency in Texas--the Cabildo of the Spanish colonial period."

Its importance was recognized in 1977 when the Texas Historical Commission nominated the Bexar County Courthouse for inclusion in the National Register of Historic Places. It is said to be the only remaining structure of the Romanesque style still in the San Antonio area. Also of interest is that the structure was designed by J. Riely Gordon, then a Texas architect who later moved to New York City to gain fame as the president of the New York Society of Architects.

When the county commissioners decided last year to go ahead with the extensive repairs and upgrades necessary to transform an 18th century landmark into a 21st century public use structure, they knew that they had to pay careful attention to the historical structure. The restoration task was made even more difficult because the courthouse had to remain fully functional with public access at all times.

To coordinate the extensive repair project, the Bexar County Commissioners Court hired 3D/International as the construction manager. The project was also divided into separate repair contracts. To help avoid construction problems, the general contractor selected a fixed scaffolding system to provide a structure shared by all of the contractors.

Revolutionary design

When the courthouse was originally constructed, the architect selected native granite and red sandstone for its exterior. The commissioners wanted to reuse and preserve these elements.

In its first phase of work, contractors needed to repair the courthouse's roof. Although its structural integrity was a concern to the engineers and designers, the most important issue was the preservation of the irreplaceable clay tile. The scaffolding system had to provide access to the repair contractor and be able to support any lifting devices needed to move repair items.

The restoration challenges caused the scaffold design engineers at BETCO, a San Antonio-based scaffold manufacturer, to develop a revolutionary design that would eventually encircle the deteriorating exterior of the historical building while not adding any weight or pressure to the historic cladding.

The engineer's design for the unique scaffolding system was based on a previous courthouse project where simple steel I-beams, resting on the scaffold supports, were used to span across the building's debilitating roof. However, a more sophisticated design was required at the Bexar County Courthouse.

To eliminate scaffolding from resting on the fragile tile roof, the scaffold engineers designed a truss network composed of six 140-foot-long trusses bolted and braced together and weighing in excess of 33,000 pounds. The massive truss systems were supported by two shoring towers to be built on the west and east sides of the courthouse.

Once laid to rest on the shoring towers, the truss would span across and hover over the existing roof on the north side of the building. Steel I-beams placed across the truss would complete the backbone to support a suspended scaffold system. This approach would enable the manufacturer's erection crew to construct scaffold on the truss to the height of the northeast and northwest towers and suspend scaffold 42 feet downward off of the steel I-beams without the risk of damage to the roof. The roof repair contractors could then perform their renovation work safely.

Six months of planning and collaboration with Ford Engineering determined the exact placement of the support towers. The erection crew rented a 365-ton crane used to hoist the truss and steel I-beams into place. The support towers were erected, the truss was assembled, and the system was put into place on May 5.

To learn more about the BETCO scaffolding system, visit their Web site at www.scaffold.com.